Hubbry Logo
Lipid emulsionLipid emulsionMain
Open search
Lipid emulsion
Community hub
Lipid emulsion
logo
8 pages, 0 posts
0 subscribers
Be the first to start a discussion here.
Be the first to start a discussion here.
Lipid emulsion
Lipid emulsion
Lipid emulsion
View on Wikipedia
from Wikipedia
A lipid emulsion (intralipid) 20%

Lipid emulsion or fat emulsion refers to an emulsion of fat for human intravenous use, to administer nutrients to critically-ill patients that cannot consume food. It is often referred to by the brand name of the most commonly used version, Intralipid, which is an emulsion containing soybean oil, egg phospholipids and glycerin, and is available in 10%, 20% and 30% concentrations. The 30% concentration is not approved for direct intravenous infusion, but should be mixed with amino acids and dextrose as part of a total nutrient admixture.

Medical uses

[edit]

Nutrition

[edit]

Intralipid and other balanced lipid emulsions provide essential fatty acids, linoleic acid (LA), an omega-6 fatty acid, alpha-linolenic acid (ALA), an omega-3 fatty acid. The emulsion is used as a component of intravenous nutrition for people who are unable to get nutrition via an oral diet. These nutrients are combined with the intention of administering parenteral nutrition, where nutrients are delivered in an alternative pathway other than the gastrointestinal tract.

Local anaesthetic toxicity

[edit]

Lipid emulsions are effective in treating experimental models of severe cardiotoxicity from intravenous overdose of local anaesthetic drugs such as bupivacaine.[1][2][3][4]

They have been effective in people unresponsive to the usual resuscitation methods. They have subsequently been used off-label in the treatment of overdose from other fat-soluble medications.[5]

Vehicle for other medications

[edit]

Propofol is dissolved in a lipid emulsion for intravenous use. Sometimes etomidate (the usual vehicle for etomidate is propylene glycol) is supplied using a lipid emulsion as a vehicle. The possibility of lipid emulsions as an alternative drug delivery medium is under works.

History

[edit]

Intravenous lipid emulsions have been used experimentally since at least the 19th century. An early product marketed in 1957 under the name Lipomul was briefly used in the United States but was subsequently withdrawn due to side effects.[6] Intralipid was invented by the Swedish physician and nutrition researcher Arvid Wretlind, and was approved for clinical use in Sweden in 1962.[7] In the United States, the Food and Drug Administration initially declined to approve the product due to prior experience with another fat emulsion. It was approved in the United States in 1972.

Research

[edit]

Intralipid is also widely used in optical experiments to simulate the scattering properties of biological tissues.[8] Solutions of appropriate concentrations of intralipid can be prepared that closely mimic the response of human or animal tissue to light at wavelengths in the red and infrared ranges where tissue is highly scattering but has a rather low absorption coefficient.

Cardioprotective agent

[edit]

Intralipid is currently being studied for its potential use as a cardioprotective agent, specifically as a treatment for ischemic reperfusion injury. The rapid return of myocardial blood supply is critical in order to save the ischemic heart, but it also has the potential to create injury due to oxidative damage (via reactive oxygen species) and calcium overload.[9] Myocardial damage with the resumption of blood flow after an ischemic event is termed "reperfusion injury".

The mitochondrial permeability transition pore (mPTP) is normally closed during ischemia, but calcium overload and increased reactive oxygen species (ROS) with reperfusion open mPTP allowing hydrogen ions to flow from the mitochondrial matrix into the cytosol. The hydrogen flux disrupts the mitochondrial membrane potential and results in mitochondrial swelling, outer membrane rupture, and the release of pro-apoptotic factors.[9][10] These changes impair mitochondrial energy production and drive cardiac myocyte apoptosis.

Intralipid (5mL/kg) provided five minutes before reperfusion delays the opening of mPTP in vivo rat models, making it a potential cardioprotective agent[11] Lou et al. (2014) found that the cardioprotection aspect of Intralipid is initiated by the accumulation of acylcarnitines in the mitochondria and involves inhibition of the electron transport chain, an increase in ROS production during early (3 min) reperfusion, and activation of the reperfusion injury salvage kinase pathway (RISK).[9] The mitochondrial accumulation of acylcarnitines (primarily palmitoyl-carnitine) inhibits the electron transport chain at complex IV, generating protective ROS.[12] The effects of ROS are both "site" and "time" sensitive, meaning that both will ultimately determine whether the ROS are beneficial or detrimental.[12] The generated ROS, which are formed from electrons leaking from the electron transport chain of the mitochondria, first act directly on mPTP to limit opening.[13] ROS then activate signalling pathways that act on the mitochondria to decrease mPTP opening and mediate protection.[13] Activation of the RISK pathway by ROS increases the phosphorylation of other pathways, such as phosphatidylinositol 3-kinase/Akt and extracellular-regulated kinase (ERK) pathways,[11] both of which are found in pools localized at the mitochondria.[14] The Akt and ERK pathways converge to alter glycogen synthase kinase-3 beta (GSK-3β) activity. Specifically, Akt and ERK phosphorylate GSK-3β, inactivating the enzyme, and inhibiting the opening of mPTP.[11] The mechanism by which GSK-3β inhibits the opening of the mPTP is controversial. Nishihara et al. (2007) proposed that it is achieved through interaction of GSK-3β with ANT subunit of mPTP, inhibiting the Cyp-D–ANT interaction, resulting in the inability of the mPTP to open.[15]

In a study by Rahman et al. (2011) Intralipid-treated rat hearts were found to required more calcium to open mPTP during ischemia-reperfusion. The cardiomyocytes are therefore, better able to tolerate the calcium overload, and increase the threshold for opening of the mPTP with the addition of Intralipid.[11]

References

[edit]
[edit]
Revisions and contributorsEdit on WikipediaRead on Wikipedia

Lipid emulsion

View on Grokipedia
from Grokipedia
A lipid emulsion is an intravenous colloidal dispersion of droplets in an aqueous phase, stabilized by emulsifying agents such as phospholipids, designed to deliver s and non-protein calories to patients unable to receive adequate nutrition enterally. These emulsions are a cornerstone of total parenteral nutrition (TPN), providing up to 30-40% of caloric needs while preventing deficiency in critically ill, postoperative, or malnourished individuals. Common formulations include soybean oil-based emulsions rich in omega-6 fatty acids like , medium- and long-chain mixtures for improved metabolic clearance, olive oil-based variants high in monounsaturated , and fish oil-containing types supplying anti-inflammatory omega-3 fatty acids such as (EPA) and (DHA). Emulsifiers, often derived from egg yolk phospholipids, maintain droplet stability with particle sizes typically under 1 micrometer to ensure and avoid risks. In nutritional applications, lipid emulsions support immune function, reduce inflammation in certain compositions, and minimize complications like hepatic steatosis when balanced with carbohydrates and . Beyond nutrition, intravenous lipid emulsion (ILE) serves as a rescue for life-threatening toxicities from lipophilic substances, particularly local anesthetic systemic toxicity (LAST) caused by agents like bupivacaine or , where it is the established . The proposed mechanism, known as the "lipid sink" or shuttle hypothesis, involves sequestration of toxins into the emulsion's lipid phase, redistributing them from vital organs to sites of metabolism like the liver and muscle, while also potentially enhancing through direct cardioprotective effects. Emerging evidence supports its use in overdoses of other lipophilic drugs, including tricyclic antidepressants, , and beta-blockers, though outcomes vary and guidelines emphasize prompt administration in scenarios. First demonstrated in animal models in 1998 and applied clinically since 2006, ILE has transformed management of these emergencies.

Overview

Definition

A lipid emulsion is a heterogeneous colloidal system comprising an oil-in-water dispersion, where droplets are suspended in an aqueous phase and stabilized by emulsifiers to prevent coalescence. These emulsions feature droplets typically ranging from 100 to 500 nm in diameter, with a mean droplet size often around 300 nm, ensuring stability and biocompatibility for therapeutic applications. The core components of a lipid emulsion include primarily in the form of triglycerides derived from sources such as or , which provide essential fatty acids and energy. Emulsifiers, such as egg yolk phospholipids, form a stabilizing around the lipid droplets to maintain dispersion, typically at a concentration of 1.2% w/v. Stabilizers like are incorporated to achieve isotonicity with , preventing osmotic imbalances during administration. Unlike general emulsions used in or , lipid emulsions for therapeutic purposes are specifically formulated for parenteral administration, rendered sterile and pyrogen-free to minimize risks of and immune such as fever. The term "lipid emulsion" historically denotes these intravenous formulations, which gained approval for human use in the 1960s following advancements in stable oil-phospholipid combinations that resolved earlier instability issues. These emulsions serve as vehicles for and toxicity reversal, with further applications detailed in subsequent sections.

Composition

Lipid emulsions for medical use are oil-in-water colloidal systems primarily composed of triglycerides as the lipid phase, emulsified in an aqueous medium. The lipid phase typically constitutes 10-30% w/v triglycerides derived from various sources, including , safflower oil, , medium-chain triglycerides (MCTs) from coconut or , and structured lipids such as rich in omega-3 fatty acids like (EPA) and (DHA). These oils provide essential fatty acids and non-protein calories, with -based formulations often containing 44-62% and 4-11% alpha-linolenic acid. Emulsifying agents, usually 1-2% phospholipids, stabilize the formulation by forming micelles around lipid droplets. Common sources include egg yolk phospholipids, though synthetic alternatives exist for allergen concerns; for instance, Intralipid 20% uses 1.2% egg yolk phospholipids. The aqueous phase includes 2-3% to achieve isotonic osmolarity of approximately 300 mOsm/L and prevent during . Antioxidants such as (dl-alpha-tocopherol, 0.15-0.3 mg/mL in emulsions) are added to inhibit , alongside minor components like sodium oleate for adjustment.
Commercial ExampleLipid Sources and ConcentrationsEmulsifier and AdditivesKey Properties
Intralipid (soybean-based)20% 1.2% egg yolk phospholipids; 2.25% glycerin; 6-8.9; osmolarity 260 mOsm/L; 2 kcal/mL
Omegaven (fish oil-based, for )10% 1.2% egg yolk phospholipids; 2.5% glycerin; 0.15-0.3 mg/mL 6-9; osmolarity 273 mOsm/L; 1.12 kcal/mL
SMOFlipid (mixed oils)6% , 6% MCTs, 5% , 3% (total 20%)1.2% egg yolk phospholipids; 2.5% glycerin; 16.3-22.5 mg/100 mL 6-9; osmolarity 270 mOsm/L; 2 kcal/mL
Clinolipid (mixed oils, approved for neonatal use in 2024)16% , 4% (total 20%)1.2% egg yolk phospholipids; 2.25% glycerin; 5-9; osmolarity 260 mOsm/L; 2 kcal/mL
Formulations vary in packaging, such as all-in-one admixtures combining , , and dextrose versus multi-chamber bags where occupy a separate compartment to enhance stability and reduce . Allergen-free options, like soy- and egg-free variants, address sensitivities, with fish oil-based products avoiding allergens. Physicochemical properties include a caloric of 9 kcal/g from , range of 6-9 for , and particle sizes of 200-500 nm to mimic chylomicrons. Shelf-life under (2-8°C) typically exceeds 12-24 months for unopened bags, though admixtures require shorter storage to maintain integrity. These emulsions serve as a source of essential fatty acids in .

Clinical Applications

Parenteral Nutrition

Lipid emulsions are a cornerstone of total parenteral nutrition (TPN), delivering essential caloric and nutritional support to patients unable to ingest food orally or enterally due to conditions like severe gastrointestinal dysfunction. They provide 20-40% of total daily calories in TPN regimens, offering a dense energy source while supplying critical essential fatty acids, including linoleic acid (an omega-6 fatty acid) and alpha-linolenic acid (an omega-3 fatty acid), to prevent deficiencies that can lead to dermatologic, hematologic, and neurologic complications during prolonged intravenous feeding. Standard dosage guidelines recommend 1-2 g/kg/day of for adults, infused continuously over 12-24 hours to prevent metabolic overload and ensure steady assimilation. Safety monitoring includes regular assessment of serum triglycerides, targeting levels below 400 mg/dL to avoid and associated risks like . In pediatric populations, such as neonates and infants, dosages start at 1-2 g/kg/day and advance to 2-3 g/kg/day based on tolerance and age-specific guidelines, with adjustments for growth requirements and lower tolerance thresholds compared to adults. These emulsions are routinely used in critically ill patients in intensive care units, post-surgical cases requiring recovery support, and malnourished individuals with chronic conditions like cancer or , where enteral intake is insufficient or contraindicated. Compared to dextrose-only TPN, lipid-inclusive formulations reduce by distributing caloric load away from glucose, thereby stabilizing blood sugar and minimizing . Emulsions containing omega-3 fatty acids further enhance immune function by attenuating excessive and supporting resolution of acute-phase responses in stressed states. Evidence from randomized controlled trials in ICU settings indicates that lipid emulsions improve nitrogen balance by promoting protein synthesis and sparing for tissue repair, while also lowering rates through better nutritional equilibrium. For example, omega-6-sparing lipid strategies have been associated with reduced nosocomial infections and shorter lengths of stay in critically ill adults. In clinical practice, lipid emulsions are compounded directly into TPN admixtures alongside and glucose to form a complete, isotonic solution that fulfills macronutrient, , and demands without requiring separate infusions. Fish oil-containing blends, when incorporated, may provide supplementary effects in patients with heightened .

Toxicity Treatment

Lipid emulsions are primarily indicated as a rescue therapy for local systemic toxicity (LAST), a potentially life-threatening condition arising from inadvertent intravascular injection or excessive dosing of local anesthetics such as bupivacaine, which can lead to and excitation or depression. The standard protocol for lipid rescue therapy involves administering a 1.5 mL/kg bolus of 20% lipid emulsion intravenously over 2-3 minutes, followed by a continuous at 0.25 mL/kg/min until hemodynamic stability is achieved, with a maximum total dose of approximately 12 mL/kg. This approach is integrated into algorithms for LAST-induced . The primarily involves the emulsion acting as a " sink," sequestering lipophilic toxins like bupivacaine into droplets, thereby reducing their free plasma concentrations and facilitating redistribution from critical tissues such as the myocardium (detailed further in the section). Beyond LAST, lipid emulsions have been used off-label for toxicities from other lipophilic drugs, including bupropion, verapamil, and antidepressants, with evidence derived from case reports demonstrating hemodynamic improvement and case series supported by animal models showing reversal of cardiovascular collapse. As of 2025, narrative reviews continue to support in overdoses of and beta-blockers, with improving evidence from case series, though randomized trials remain needed. The American Society of Regional Anesthesia and Pain Medicine (ASRA) provides the primary guidelines endorsing lipid emulsion therapy for LAST, recommending its immediate use in cases of cardiovascular collapse, with reported success rates exceeding 70% in resuscitating patients from associated with local anesthetic overdose based on registry data and systematic reviews. Contraindications include known severe to soy or egg components in the emulsion, as most formulations contain and egg phospholipids. Additionally, administration can interfere with laboratory tests, such as causing falsely elevated levels due to lipemia, necessitating careful timing of blood draws.

Drug Delivery

Lipid emulsions serve as effective vehicles for the delivery of lipophilic drugs, enhancing their in aqueous environments and enabling intravenous administration without the need for toxic organic solvents. By encapsulating hydrophobic active pharmaceutical ingredients within the oil droplets stabilized by emulsifiers such as phospholipids, these formulations improve drug and reduce local tissue irritation at the infusion site compared to traditional aqueous solutions. A prominent example is , formulated as Diprivan, an injectable containing 1% in a oil-based vehicle with as the emulsifier, which allows for rapid onset of while minimizing pain on injection associated with aqueous formulations. Similarly, is available in forms like Diazemuls, which demonstrated pain on injection in only 0.4% of 2,435 patients, with no associated skin reddening or tenderness. has also been incorporated into emulsions to facilitate safe intravenous delivery, avoiding glycol-related adverse effects in conventional preparations. These emulsions offer advantages including sustained drug release due to partitioning into the phase, which prolongs circulation time, and reduced toxicity by serving as cremophor-free alternatives that avoid solvent-induced . In , lipid-based formulations, such as nanoemulsions, have shown clinical evidence of decreased infusion site reactions and overall compared to cremophor EL-containing Taxol, with approvals in regions like for products such as Lipusu demonstrating comparable antitumor efficacy but improved tolerability. Nanoemulsions further extend applications to oral and topical routes, where lipid droplets enhance across mucosal barriers and , improving absorption of poorly soluble actives without gastrointestinal irritation. In , are typically incorporated into the core via solubilization in the oil phase during or adsorbed onto droplet surfaces, followed by rigorous stability testing to monitor for , droplet coalescence, or creaming over storage at various temperatures. Phospholipids aid in encapsulation by forming a stabilizing interfacial layer, though excessive loading can compromise integrity. Despite these benefits, limitations include potential drug-lipid interactions that may alter , such as reduced hypnotic potency of certain anesthetics when co-administered with lipid emulsions, necessitating careful compatibility assessments to maintain therapeutic .

Pharmacology

Mechanisms of Action

In , lipid emulsions serve as a source of s and energy, undergoing hydrolysis primarily by endothelial to release free fatty acids that are taken up by tissues for beta-oxidation and incorporation into cell membranes. This process mimics the metabolism of endogenous chylomicrons, with the emulsions' cores being cleaved to provide non-esterified fatty acids bound to for transport, thereby preventing essential fatty acid deficiency by supplying linoleic and alpha-linolenic acids at levels of at least 1-3.2% of total caloric intake. Medium-chain s within some emulsions are hydrolyzed more rapidly than long-chain variants, enhancing their availability for mitochondrial beta-oxidation and ATP production. In the context of toxicity treatment, particularly for local anesthetic systemic toxicity, lipid emulsions operate via the partitioning , wherein the emulsion droplets act as a lipid sink that preferentially binds lipophilic toxins such as bupivacaine (logP ≈ 3.4), sequestering them from aqueous plasma and tissue compartments to expand the volume of distribution and reduce free drug concentrations at target sites like the myocardium and . This redistribution lowers the toxin's availability to bind sodium channels, mitigating cardiovascular collapse, as evidenced by rapid reductions in plasma bupivacaine levels following emulsion infusion in animal models. The binding affinity is quantified by the K=[drug in lipid][drug in aqueous]K = \frac{[\text{drug in lipid}]}{[\text{drug in aqueous}]}, which exceeds 100 for effective sinks with bupivacaine showing values around 1,870 in soybean oil-based s like Intralipid. For , lipid emulsions enhance the solubility and absorption of lipophilic payloads (logP > 5) by promoting their incorporation into chylomicron-like particles within enterocytes, facilitating lymphatic uptake that bypasses hepatic first-pass and increases systemic . This mechanism improves membrane permeability through association with fatty acid-binding proteins and lipid transporters, allowing sustained release and targeted delivery, as seen with formulations like achieving 83-84% via lymph in preclinical studies. At the cellular level, lipid emulsions exert effects by modulating (PPAR) activity; for instance, Intralipid blocks lysophosphatidylcholine-induced inhibition of PPARγ in dendritic cells, thereby suppressing maturation and promoting resolution of inflammatory responses. In cardioprotection, they activate voltage-gated calcium channels to increase intracellular Ca²⁺ levels, enhancing and countering toxin-induced depression, while also stimulating the PI3K/Akt pathway to inhibit mitochondrial permeability transition and . Emulsion composition influences these actions; omega-3-rich variants, containing eicosapentaenoic and docosahexaenoic acids from , upregulate such as resolvins, protectins, and maresins, which actively resolve by modulating immune cell function and reducing pro-inflammatory production in settings.

Pharmacokinetics

Lipid emulsions administered intravenously achieve immediate , entering the systemic circulation directly without gastrointestinal processing. In contrast, oral lipid emulsions are subject to gastrointestinal , where gastric and pancreatic lipases initiate the breakdown of triglycerides into free fatty acids and monoglycerides, facilitating absorption primarily via the intestinal as chylomicron-like particles. Following intravenous infusion, lipid emulsions rapidly distribute to tissues, with significant uptake by the , including the liver, , and lungs, mimicking the behavior of endogenous chylomicrons. The emulsion particles, typically 200-400 nm in diameter, acquire apolipoproteins such as apo-E and apo-CII from high-density and very low-density lipoproteins within minutes, enabling receptor-mediated distribution. The plasma of these chylomicron-like particles is short, ranging from 10-20 minutes for soybean oil-based emulsions like Intralipid, reflecting rapid clearance. Metabolism of intravenous lipid emulsions occurs primarily through hydrolysis by lipoprotein lipase in peripheral tissues and hepatic lipase in the liver, converting triglycerides to free fatty acids and sn-2 monoglycerides for utilization or re-esterification. Phospholipids in the emulsion are similarly metabolized to lysophospholipids and free fatty acids by phospholipases. Clearance rates vary by emulsion composition; medium-chain triglyceride-containing formulations exhibit faster and elimination compared to long-chain triglyceride-based ones, with half-lives around 34 minutes for mixed emulsions like SMOFlipid versus 59 minutes for pure long-chain types. Excretion of lipid emulsion components is predominantly hepatic, with remnants processed via low-density lipoprotein receptors and eliminated through biliary secretion as cholesterol esters, followed by fecal elimination; renal excretion remains minimal, accounting for less than 1% of the dose due to the hydrophobic nature of lipids. Several factors influence . impairs activity, prolonging clearance and extending beyond 30 minutes by saturating metabolic pathways. In pediatric patients, is generally faster than in adults due to higher activity, though preterm neonates may exhibit slower clearance. Lipid emulsions interact with lipophilic drugs by sequestering them into emulsion droplets, increasing and potentially delaying their clearance, as observed with anesthetics like bupivacaine. Pharmacokinetics can be monitored through plasma clearance rates, assessed via turbidimetry or nephelometry to measure triglyceride levels and lipemic index, ensuring safe infusion rates and detecting impaired elimination.

Administration and Safety

Preparation and Delivery

Lipid emulsions for clinical use are manufactured through a multi-step process that ensures sterility, uniformity, and stability. The primary method involves high-pressure homogenization, where the oil-in-water emulsion is subjected to pressures up to 500 bar to reduce droplet sizes to less than 400 nm, achieving the fine particle distribution required for safe intravenous administration. This step follows the initial mixing of lipid sources, emulsifiers such as phospholipids, and aqueous phases, with subsequent terminal sterilization or aseptic processing to eliminate microbial contaminants. The final product is aseptically filled into glass vials or flexible plastic bags under controlled environmental conditions to prevent contamination. Quality control measures are rigorously applied to verify the emulsion's safety and efficacy. Sterility is confirmed through testing per (USP) Chapter <71>, which involves incubation of samples in growth media to detect viable microorganisms. , typically using light scattering techniques, ensures compliance with USP Chapter <729> limits for globule size distribution, with a volume-weighted mean diameter below 500 nm and minimal large-diameter globules exceeding 5 μm to reduce risk. Endotoxin levels are limited to less than 0.5 EU/mL via the test outlined in USP Chapter <85>, preventing pyrogenic reactions. Storage conditions are critical to maintain emulsion integrity, as exposure to heat, light, or oxygen can promote peroxidation and . Unopened lipid emulsions are stored refrigerated at 2–8°C and protected from , with a typical of up to 24 months from the date of manufacture, depending on the formulation. Once opened or compounded, they should be used promptly or refrigerated for short-term stability, avoiding freezing which may cause irreversible damage to the emulsion structure. Delivery of lipid emulsions occurs via intravenous , suitable for both central and peripheral lines due to their low osmolarity (typically 270–410 mOsm/L). pumps are employed to regulate flow rates precisely, with a maximum recommended rate of 0.1 g/kg/hour to minimize risks such as fat overload syndrome. Administration begins slowly, often at 0.02–0.05 g/kg/hour for the first 15–30 minutes, to monitor for tolerance before increasing to the target rate over 12–24 hours. Compatibility considerations guide co-administration practices. Lipid emulsions are generally compatible for Y-site with electrolytes and many aqueous solutions, provided the remains stable (around 8 for optimal emulsifier function). However, they are incompatible with , which can cause immediate precipitation and emulsion destabilization, necessitating separate lines or sequential administration. In settings, lipid emulsions are often compounded into total (TPN) admixtures under sterile conditions, combining them with , dextrose, and micronutrients in a single bag for convenience. Patients receive education on proper handling, including of the bag for signs of instability such as creaming (layering of lipid droplets on top) or cracking ( into oily and aqueous layers), which indicate compromised stability and require discarding the solution. Such inspections, performed before each , help prevent infusion of unstable emulsions that could lead to adverse events.

Adverse Effects

Lipid emulsions used in parenteral nutrition can elicit a range of adverse effects, primarily related to , infusion dynamics, and component sensitivities. Common effects include , where serum levels exceed 500 mg/dL, often resulting from infusion rates surpassing 0.1 g/kg/hour or cumulative doses approaching metabolic limits. Additional frequent manifestations encompass , fever, and infusion-related due to transient inflammatory responses or fat overload. More serious risks arise from excessive or prolonged exposure, notably fat overload syndrome, which presents with hepatomegaly, splenomegaly, fever, and potential organ dysfunction when daily doses exceed 2.5 g/kg. This syndrome stems from overwhelmed lipid clearance mechanisms, leading to fat accumulation in tissues. Pulmonary embolism represents another grave concern, particularly in vulnerable populations like neonates, where large lipid droplets can obstruct pulmonary vasculature; autopsy findings have shown lipid deposits in cases involving prolonged infusions. Allergic reactions, including anaphylaxis, occur in response to emulsifiers such as egg lecithin or soy phospholipids, with a low incidence (<1%); these hypersensitivity events manifest as urticaria, dyspnea, or hypotension shortly after initiation. Alternatives with different lipid compositions, such as olive oil-based emulsions, may be considered, but patients should be screened for allergies to components like egg or soy. Long-term administration may result in excess essential fatty acids, particularly omega-6 polyunsaturated fatty acids from soybean-based formulations, contributing to via reduced clearance by up to 40% after repeated dosing. Routine monitoring through is essential to detect early hepatic stress or . Contraindications encompass severe , where baseline triglyceride elevations contraindicate use, and , especially when accompanied by , as lipids may exacerbate pancreatic inflammation. Precautions are warranted in , where impaired heightens complication risks. Effective management prioritizes dose reduction to below 2 g/kg/day in at-risk patients, alongside inline using 1.2 μm filters to eliminate oversized droplets and prevent . Infusion should be discontinued if triglycerides surpass 1000 mg/dL, with temporary withholding typically resolving elevations within 5 days. Meta-analyses of total regimens report severe adverse events, such as fat overload or , in fewer than 2% of cases, underscoring the overall favorable safety profile when guidelines are followed.

History

Early Development

Early attempts at intravenous fat administration date back to the , when English naturalist William Courten infused into dogs in 1712, resulting in fatal due to the oil's insolubility and tendency to form large droplets. In the , further experiments included Edward Hodder's 1873 infusion of into patients, where some recovered but many suffered severe adverse effects from instability and contamination. By the , researchers in the United States and developed numerous -based emulsions using various emulsifiers, but these consistently failed in clinical trials due to droplet aggregation, risks, and pyrogenic reactions, preventing safe human use. The drive for viable intravenous lipid emulsions intensified during and after , amid food shortages and the need for protein-sparing to support malnourished patients unable to eat orally. In the 1950s, Swedish physician and biochemist Arvid Wretlind addressed these challenges by formulating a stable emulsion using purified as the lipid source and egg yolk phospholipids as the emulsifier, creating Intralipid to mimic natural chylomicrons and ensure biocompatibility. This innovation stemmed from Wretlind's work at , where he refined earlier concepts to provide essential fatty acids and calories without the toxicity of prior formulations. Initial hurdles included preventing droplet coalescence and eliminating pyrogen contamination through rigorous sterilization and quality controls, which Wretlind overcame via optimized manufacturing processes. in dogs demonstrated safe hepatic clearance and minimal adverse effects, confirming the emulsion's tolerability at doses up to 3 g/kg body weight daily. The first commercial version, 10% Intralipid with 1.2% phospholipids, was approved for clinical use in in 1962 following successful trials in malnourished patients, who showed improved nitrogen balance and . It received U.S. FDA approval in 1975 after additional refinements to address regulatory concerns over long-term safety.

Key Milestones

Building on the foundational work of Arvid Wretlind in the 1960s, subsequent decades saw significant refinements in lipid emulsion formulations to enhance clinical utility and patient tolerance in parenteral nutrition. In the 1980s, advancements included the introduction of 20% lipid emulsions, such as Liposyn 20% by Abbott in 1981, which allowed for more concentrated delivery of calories and essential fatty acids while reducing fluid volume load. Concurrently, medium-chain triglyceride/long-chain triglyceride (MCT/LCT) blends emerged, exemplified by Lipofundin in the mid-1980s, offering improved metabolic clearance and reduced risk of hypertriglyceridemia compared to pure LCT emulsions. The 1990s and early 2000s marked the advent of omega-3 enriched emulsions, with Omegaven (a oil-based lipid emulsion) receiving approval in in 1998 for use in preventing parenteral nutrition-associated in pediatric patients requiring long-term support. In the 2000s, lipid s expanded beyond into toxicology, as the American Society of Regional Anesthesia and Pain Medicine (ASRA) incorporated intravenous lipid therapy into its 2010 practice advisory for treating local anesthetic systemic toxicity (LAST), recommending a 1.5 mL/kg bolus of 20% followed by infusion to sequester lipophilic toxins. regulatory progress included the 2016 FDA approval of SMOFlipid, a mixed-lipid combining , MCT, , and , providing a balanced profile to mitigate and deficiency in adults. This was followed by FDA approval of SMOFlipid for pediatric patients in 2022. In 2018, Omegaven received FDA approval for pediatric use in parenteral -associated . Further expansion occurred in 2024 with FDA approval of Clinolipid, another mixed-oil , for neonatal and pediatric patients. From the 2010s onward, innovations focused on advanced delivery systems, including lipid nanoemulsions for , which improved of poorly soluble drugs through enhanced solubility and lymphatic uptake, as evidenced in formulations developed for therapeutics like . The in 2020 disrupted supply chains, leading to shortages of intravenous lipid emulsions, particularly for formulations, which strained availability and prompted contingency protocols for rationing. Further innovations encompassed structured lipids, such as randomized triglycerides combining MCT and LCT on the same backbone for optimized oxidation and reduced liver burden, and all-in-one total bags, which integrate , , and carbohydrates to minimize handling steps and contamination risks during preparation and administration.

Research

Cardioprotective Effects

Lipid emulsions, particularly those enriched with omega-3 fatty acids, have demonstrated cardioprotective effects in preclinical models of myocardial ischemia-reperfusion . In rat models, pretreatment with ω-3 fat emulsion significantly reduced infarct size by approximately 25-30%, alongside decreased incidence of ventricular arrhythmias, attributed to the anti-arrhythmic properties of (EPA) and (DHA). Similarly, acute administration of n-3 rich emulsions in murine ischemia-reperfusion models provided cardioprotection by mitigating and apoptotic pathways in cardiomyocytes. These findings highlight the potential of lipid emulsions to limit myocardial damage during ischemic events through omega-3 mediated stabilization of . The cardioprotective mechanisms of lipid emulsions involve stabilization and modulation of activity, including inhibition of excessive calcium influx during reperfusion. Omega-3 components incorporate into cardiac cell membranes, enhancing fluidity and reducing susceptibility to arrhythmias by altering sodium and function. In models, lipid emulsions reverse mitochondrial calcium overload and restore , a process analogous to ischemia-reperfusion protection. Some randomized trials suggest intralipid postconditioning may attenuate myocardial markers like , though meta-analytic evidence from five RCTs is mixed with no overall significant reduction. For instance, in off-pump CABG patients, 1.5 mL/kg intralipid infusion after sternotomy decreased ischemic markers, including , though not kinase-MB. Human studies, primarily randomized controlled trials (RCTs) in , suggest perioperative lipid emulsion infusion may lower postoperative arrhythmia rates. Some meta-analyses suggest a reduction in post-operative incidence with omega-3 supplementation, including intravenous forms, linked to effects on atrial tissue. Perioperative infusions of -based emulsions (0.2 g/kg) in CABG patients increased plasma EPA/DHA levels and reduced , correlating with fewer arrhythmias over 48 hours. However, results vary; one RCT found no significant prevention of with infusion post-CABG, underscoring the need for optimized dosing. Fish oil-based lipid emulsions are preferred for cardioprotection due to their high EPA and DHA content, typically administered at 1-2 g per dose to achieve therapeutic plasma levels. These formulations, such as Omegaven 10%, deliver 0.1-0.2 g/kg EPA/DHA intravenously, promoting incorporation without adverse hemodynamic effects. Doses around 1.8 g EPA daily have shown plaque stabilization benefits in coronary patients when combined with standard therapy. Despite promising data, limitations persist; clinical trials in chronic yield mixed results, with some showing no significant improvement in or symptoms from omega-3 emulsions. Lipid emulsions lack FDA approval for cardioprotective indications beyond nutritional support. As of 2025, ongoing phase II trials explore adjunctive uses, such as emulsions in high-risk to reduce , though specific STEMI applications remain investigational.

Emerging Therapeutic Uses

Lipid emulsions enriched with omega-3 fatty acids have shown promise in managing and by mitigating storms, particularly in (ARDS) models, through reductions in pro-inflammatory markers such as interleukin-6 (IL-6) and tumor necrosis factor-alpha (TNF-α). A 2024 in critically ill patients demonstrated that omega-3 supplementation in significantly lowered inflammatory biomarkers like and IL-6, alongside improvements in clinical outcomes including reduced ventilator days. Meta-analyses of clinical trials indicate that omega-3 polyunsaturated fatty acids (PUFAs) in enteral formulations for ARDS patients enhance oxygenation parameters, such as the PaO2-to-FiO2 ratio, by up to 20% in early and late phases, potentially decreasing ICU length of stay without altering overall mortality rates. Meta-analyses, including a 2022 review of RCTs, indicate omega-3 lipid emulsions may reduce mortality in (RR 0.74), attributed to immunomodulatory effects on hyper; a 2024 narrative review notes a trend toward reduced 28-day mortality without increased harm. As of 2025, a narrative review highlights potential benefits of omega-3 emulsions in critical care. In neurological disorders, lipid emulsion formulations akin to propofol have been investigated for sedation protocols that minimize respiratory depression, offering alternatives for prolonged use in intensive care. Fospropofol, a delivered via , demonstrates neuroprotective potential in preclinical models of cerebral ischemia and by modulating cerebral blood flow and reducing neuronal damage, potentially leveraging transient blood-brain barrier (BBB) permeability to enhance . Studies indicate that propofol-based emulsions can increase BBB permeability at clinical doses, facilitating targeted transport of therapeutics across the barrier in scenarios without exacerbating respiratory compromise when dosed appropriately. For cancer therapy, doxorubicin-loaded nanoemulsions have emerged as a strategy to reduce while improving tumor targeting through the enhanced permeability and retention (EPR) effect in preclinical models. These nanoemulsions encapsulate within matrices, achieving high drug loading and sustained release, which preclinical data show minimizes cardiac toxicity by limiting systemic exposure and enhances antitumor efficacy via passive accumulation in tumor vasculature leaky to nanoparticles larger than 50 nm. and animal studies confirm that such formulations reduce -induced markers by over 50% compared to free drug, while exploiting the EPR effect for up to 10-fold higher intratumoral drug concentrations. Lipid emulsions encapsulating antimicrobials like have demonstrated enhanced penetration into , addressing limitations in treating persistent infections such as those caused by (MRSA). Fusogenic liposomes loaded with exhibit superior eradication, reducing viable by 3-4 logs in mature S. aureus biofilms compared to free , due to lipid-mediated fusion and intracellular delivery. Preclinical evaluations of lipid-coated hybrid nanoparticles further validate this approach, showing improved disruption in infections with minimal to host cells. Recent developments include lipid nanoparticles (LNPs) as vectors for , with ongoing clinical trials for RNA-based and CRISPR-enabled editing as of 2025. LNPs facilitate efficient delivery, protecting payloads from degradation and enabling targeted , as evidenced by FDA approvals for LNP-delivered therapies in rare genetic disorders. In , omega-3-enriched lipid emulsions accelerate by promoting epithelialization and deposition, with topical applications showing 20-30% faster closure rates in animal models through anti-inflammatory and pro-resolving lipid mediators. Multifunctional lipid nanoparticles further support tissue regeneration by controlled release of growth factors at sites. Despite these advances, challenges in and long-term safety persist for lipid emulsions in emerging applications, including variability in reproducibility and potential from repeated dosing. As of 2025, preclinical studies, including NIH-funded research on LNP delivery, address concerns, such as lipid accumulation in organs.

References

  1. https://www.mayoclinic.org/drugs-supplements/fat-emulsion-intravenous-route/description/drg-20063792
  2. https://www.frontiersin.org/journals/pharmacology/articles/10.3389/fphar.2020.00506/full
  3. https://www.ncbi.nlm.nih.gov/books/NBK549897/
  4. https://www.sciencedirect.com/topics/chemical-engineering/lipid-emulsion
  5. https://www.drugfuture.com/pharmacopoeia/usp32/pub/data/v32270/usp32nf27s0_c729.html
  6. https://pmc.ncbi.nlm.nih.gov/articles/PMC3011075/
  7. https://med.virginia.edu/ginutrition/wp-content/uploads/sites/199/2014/06/IVLE-August-17.pdf
  8. https://www.gastrojournal.org/article/0016-5085%2886%2990884-X/pdf
  9. https://www.accessdata.fda.gov/drugsatfda_docs/label/2022/018449s049lbl.pdf
  10. https://publications.aap.org/neoreviews/article/21/2/e109/92240/Intravenous-Lipid-Emulsions-in-the-NICU
  11. https://pmc.ncbi.nlm.nih.gov/articles/PMC7201073/
  12. https://www.freseniuskabinutrition.com/products/intralipid/
  13. https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=5d9d0b24-e139-48bf-ab2d-536fb59cf8e0
  14. https://www.accessdata.fda.gov/drugsatfda_docs/label/2020/207648s003lbl.pdf
  15. https://www.accessdata.fda.gov/drugsatfda_docs/label/2021/204508s015lbl.pdf
  16. https://www.bapen.org.uk/education/nutrition-support/parenteral-nutrition/parenteral-nutrition-formulation/
  17. https://pmc.ncbi.nlm.nih.gov/articles/PMC4561835/
  18. https://aspenjournals.onlinelibrary.wiley.com/doi/full/10.1002/ncp.11278
  19. https://www.drugs.com/dosage/fat-emulsion.html
  20. https://www.hopkinsmedicine.org/-/media/files/allchildrens/clinical-pathways/iv-lipid-emulsions-management-clinical-pathway-5_3_24.pdf
  21. https://aspenjournals.onlinelibrary.wiley.com/doi/10.1002/jpen.1733
  22. https://www.mdpi.com/2072-6643/12/6/1566
  23. https://pmc.ncbi.nlm.nih.gov/articles/PMC4810105/
  24. https://ccforum.biomedcentral.com/articles/10.1186/s13054-022-03896-3
  25. https://jtd.amegroups.org/article/view/18833/html
  26. https://www.ncbi.nlm.nih.gov/books/NBK559036/
  27. 00037-7/fulltext
  28. https://asra.com/docs/default-source/guidelines-articles/local-anesthetic-systemic-toxicity-rgb.pdf?sfvrsn=33b348e_2
  29. https://pmc.ncbi.nlm.nih.gov/articles/PMC10939703/
  30. https://jmedicalcasereports.biomedcentral.com/articles/10.1186/1752-1947-5-399
  31. https://www.thieme-connect.com/products/ejournals/abstract/10.1055/s-0039-1693483
  32. https://www.longdom.org/open-access/tricyclic-antidepressant-drug-intoxication-is-there-a-role-for-lipid-emulsion-therapy-52172.html
  33. https://annalsofintensivecare.springeropen.com/articles/10.1186/s13613-025-01601-5
  34. https://www.clintox.org/wp-content/uploads/2016/05/Systematic-review-of-the-effect-of-intravenous-lipid-emulsion-therapy-for-local-anesthetic-toxicity.pdf
  35. https://www.tandfonline.com/doi/full/10.1080/15563650.2017.1288911
  36. https://www.accessdata.fda.gov/drugsatfda_docs/label/2025/017643s085%2C018449s054%2C019942s025%2C020248s031lbl.pdf
  37. https://pmc.ncbi.nlm.nih.gov/articles/PMC4469727/
  38. https://pmc.ncbi.nlm.nih.gov/articles/PMC4590796/
  39. https://www.accessdata.fda.gov/drugsatfda_docs/label/2017/019627s066lbl.pdf
  40. https://pmc.ncbi.nlm.nih.gov/articles/PMC10224337/
  41. https://pmc.ncbi.nlm.nih.gov/articles/PMC7075337/
  42. https://pmc.ncbi.nlm.nih.gov/articles/PMC5723209/
  43. https://pmc.ncbi.nlm.nih.gov/articles/PMC11597327/
  44. https://pmc.ncbi.nlm.nih.gov/articles/PMC6779084/
  45. https://pubmed.ncbi.nlm.nih.gov/9756113/
  46. https://pmc.ncbi.nlm.nih.gov/articles/PMC3709755/
  47. https://pmc.ncbi.nlm.nih.gov/articles/PMC10658092/
  48. https://pubmed.ncbi.nlm.nih.gov/8576643/
  49. https://www.mdpi.com/1999-4923/15/5/1396
  50. https://pubmed.ncbi.nlm.nih.gov/16857549/
  51. https://www.researchgate.net/publication/23980630_Binding_of_Long-lasting_Local_Anesthetics_to_Lipid_Emulsions
  52. https://pmc.ncbi.nlm.nih.gov/articles/PMC7103284/
  53. https://www.frontiersin.org/journals/drug-delivery/articles/10.3389/fddev.2023.1232012/full
  54. https://pubmed.ncbi.nlm.nih.gov/14688309/
  55. https://www.frontiersin.org/journals/medicine/articles/10.3389/fmed.2021.756866/full
  56. https://pubmed.ncbi.nlm.nih.gov/32049394/
  57. https://pubmed.ncbi.nlm.nih.gov/26607242/
  58. https://pmc.ncbi.nlm.nih.gov/articles/PMC10244607/
  59. https://journals.sagepub.com/doi/10.1177/0004563221990686
  60. https://pmc.ncbi.nlm.nih.gov/articles/PMC2795378/
  61. https://pubmed.ncbi.nlm.nih.gov/23460566/
  62. https://www.mdpi.com/1999-4923/14/8/1603
  63. https://www.usp.org/sites/default/files/usp/document/harmonization/gen-method/q11_pf_ira_34_6_2008.pdf
  64. https://www.usp.org/harmonization-standards/pdg/general-methods/bacterial-endotoxins
  65. https://www.accessdata.fda.gov/drugsatfda_docs/label/2023/017643s083%2C018449s050s051%2C019942s021%2C020248s027s028lbl.pdf
  66. https://publications.ashp.org/display/book/9781585286720/chPT002.pdf
  67. https://publications.ashp.org/display/book/9781585285402/back-4.pdf
  68. https://www.mskcc.org/cancer-care/patient-education/home-total-parenteral-nutrition
  69. https://www.clintox.org/wp-content/uploads/2016/05/Systematic-review-of-clinical-adverse-events-reported-after-acute-intravenous-lipid-emulsion-administration.pdf
  70. https://publications.aap.org/pediatrics/article/128/4/e1025/30779/Hypersensitivity-to-Total-Parenteral-Nutrition-Fat
  71. https://aspenjournals.onlinelibrary.wiley.com/doi/abs/10.1002/ncp.10443
  72. https://eajm.org/Content/files/sayilar/232/205-212.pdf
  73. https://aspenjournals.onlinelibrary.wiley.com/doi/am-pdf/10.1002/jpen.1737
  74. https://pubmed.ncbi.nlm.nih.gov/21799190/
  75. https://karger.com/anm/article/80/5/253/910560/Safety-Profile-of-Lipid-Emulsion-in-Clinical
  76. https://pmc.ncbi.nlm.nih.gov/articles/PMC5409727/
  77. https://pubmed.ncbi.nlm.nih.gov/6788972/
  78. https://aspenjournals.onlinelibrary.wiley.com/doi/10.1177/0148607114560825
  79. https://www.accessdata.fda.gov/drugsatfda_docs/nda/98/020181_S000_CLIN_PHARM_BIOPHARM.PDF
  80. https://ajcn.nutrition.org/article/S0002-9165%2823%2928052-1/pdf
  81. https://www.accessdata.fda.gov/drugsatfda_docs/nda/2018/210589Orig1s000OtherR.pdf
  82. https://asra.com/news-publications/asra-updates/blog-landing/guidelines/2020/11/01/checklist-for-treatment-of-local-anesthetic-systemic-toxicity
  83. https://www.accessdata.fda.gov/drugsatfda_docs/nda/2016/207648Orig1s000Admincorres.pdf
  84. https://www.fresenius-kabi.com/us/news-and-events/fresenius-kabi-announces-fda-approval-of-smoflipid--lipid-inject
  85. https://www.baxter.com/baxter-newsroom/baxter-secures-fda-approval-clinolipid-lipid-injectable-emulsion-neonatal-and
  86. https://www.semanticscholar.org/paper/Composition-of-Lipid-Based-Nanoemulsion-for-Oral-of-Vaishali-Lalita/3291e7e4d35b54b0d5bdbcba8245420350655eee
  87. https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0331651
  88. https://www.sciencedirect.com/science/article/abs/pii/S089990079900249X
  89. https://pmc.ncbi.nlm.nih.gov/articles/PMC8309029/
  90. https://www.sciencedirect.com/science/article/pii/S0753332219314532
  91. https://www.annualreviews.org/content/journals/10.1146/annurev-nutr-082018-124539
  92. https://karger.com/crm/article/8/3/173/87057/3-Polyunsaturated-Fatty-Acid-Postconditioning
  93. https://www.ahajournals.org/doi/10.1161/circep.109.880773
  94. https://link.springer.com/article/10.1007/s10557-024-07594-w
  95. https://asja.springeropen.com/articles/10.1186/s42077-021-00174-2
  96. https://www.sciencedirect.com/science/article/abs/pii/S0261561416301091
  97. https://www.sciencedirect.com/science/article/pii/S0002916523054035
  98. https://pubmed.ncbi.nlm.nih.gov/25027101/
  99. https://pmc.ncbi.nlm.nih.gov/articles/PMC4404291/
  100. https://pmc.ncbi.nlm.nih.gov/articles/PMC8767101/
  101. https://www.ahajournals.org/doi/10.1161/cir.0000000000000482
  102. https://www.clinicaltrials.gov/study/NCT06279793
  103. https://www.sciencedirect.com/science/article/pii/S0964339725002903
  104. https://www.researchgate.net/publication/383940037_Impact_of_Omega-3_Fatty_Acid_Supplementation_in_Parenteral_Nutrition_on_Inflammatory_Markers_and_Clinical_Outcomes_in_Critically_Ill_COVID-19_Patients_A_Randomized_Controlled_Trial
  105. https://pmc.ncbi.nlm.nih.gov/articles/PMC10019281/
  106. https://pmc.ncbi.nlm.nih.gov/articles/PMC9185164/
  107. https://ccforum.biomedcentral.com/articles/10.1186/s13054-024-05053-4
  108. https://pubs.acs.org/doi/10.1021/acsptsci.4c00745
  109. https://pmc.ncbi.nlm.nih.gov/articles/PMC12240524/
  110. https://pubmed.ncbi.nlm.nih.gov/39044046/
  111. https://pubs.acs.org/doi/10.1021/acsomega.2c04238
  112. https://www.mdpi.com/2227-9059/10/6/1259
  113. https://www.researchgate.net/publication/369119156_Recent_Preclinical_and_Clinical_Progress_in_Liposomal_Doxorubicin
  114. https://pmc.ncbi.nlm.nih.gov/articles/PMC6895244/
  115. https://pubs.acs.org/doi/10.1021/acsomega.2c04008
  116. https://bmcbiotechnol.biomedcentral.com/articles/10.1186/s12896-024-00874-1
  117. https://www.cell.com/molecular-therapy-family/methods/fulltext/S2329-0501(25)00113-5
  118. https://finance.yahoo.com/news/lipid-nanoparticles-gene-therapy-market-130500487.html
  119. https://pubmed.ncbi.nlm.nih.gov/29264725/
  120. https://www.sciencedirect.com/science/article/pii/S0001868623001690
  121. https://reporter.nih.gov/project-details/11203689
Add your contribution
Related Hubs
User Avatar
No comments yet.