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Capsule (pharmacy)
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In the manufacture of pharmaceuticals, encapsulation refers to a range of dosage forms—techniques used to enclose medicines—in a relatively stable shell known as a capsule, allowing them to, for example, be taken orally or be used as suppositories. The two main types of capsules are:
- Hard-shelled capsules, which contain dry, powdered ingredients or miniature pellets made by e.g. processes of extrusion or spheronization. These are made in two-halves: a smaller-diameter "body" that is filled and then sealed using a larger-diameter "cap".
- Soft-shelled capsules, primarily used for oils and for active ingredients that are dissolved or suspended in oil.
Both of these classes of capsules are made from aqueous solutions of gelling agents, such as animal protein (mainly gelatin) or plant polysaccharides or their derivatives (such as carrageenans and modified forms of starch and cellulose). Other ingredients can be added to the gelling agent solution including plasticizers such as glycerin or sorbitol to decrease the capsule's hardness, coloring agents, preservatives, disintegrants, lubricants and surface treatment.
Since their inception, capsules have been viewed by consumers as the most efficient method of taking medication.[citation needed] For this reason, producers of drugs such as OTC analgesics wanting to emphasize the strength of their product developed the "caplet", a portmanteau of "capsule-shaped tablet",[1] to tie this positive association to more efficiently produced tablet pills, as well as being an easier-to-swallow shape than the usual disk-shaped tablet medication.
Single-piece gel encapsulation ("soft capsules")
[edit]
In 1833, Mothes and Dublanc were granted a patent for a method to produce a single-piece gelatin capsule that was sealed with a drop of gelatin solution. They used individual iron molds for their process, filling the capsules individually with a medicine dropper. Later on, methods were developed that used sets of plates with pockets to form the capsules. Although some companies still use this method, the equipment is no longer produced commercially. All modern soft-gel encapsulation uses variations of a process developed by R. P. Scherer in 1933. His innovation used a rotary die to produce the capsules. They were then filled by blow molding. This method was high-yield, consistent, and reduced waste.[citation needed]
Softgels can be an effective delivery system for oral drugs, especially poorly soluble drugs. This is because the fill can contain liquid ingredients that help increase the solubility or permeability of the drug across the membranes in the body. Liquid ingredients are difficult to include in any other solid dosage form, such as a tablet. Softgels are also highly suited to potent drugs (for example, where the dose is <100 μg), where the highly reproducible filling process helps ensure each softgel has the same drug content, and because the operators are not exposed to any drug dust during the manufacturing process.
In 1949, the Lederle Laboratories division of the American Cyanamid Company developed the "Accogel" process, allowing powders to be accurately filled into soft gelatin capsules.
Two-piece gel encapsulation ("hard capsules")
[edit]
James Murdoch of London patented the two-piece telescoping gelatin capsule in 1847.[2] The capsules are made in two parts by dipping metal pins in the gelling agent solution. The capsules are supplied as closed units to the pharmaceutical manufacturer. Before use, the two halves are separated, and the capsule is filled with powder or more normally pellets made by the process of extrusion and spheronization (either by placing a compressed slug of powder into one half of the capsule or by filling one half of the capsule with loose powder) and the other half of the capsule is pressed on. With the compressed slug method, weight varies less between capsules. However, the machinery required to manufacture them is more complex.[3]
The powder or spheroids inside the capsule contains the active ingredients and any excipients, such as binders, disintegrants, fillers, glidant, and preservatives.
Manufacturing materials
[edit]Gelatin capsules, informally called gel caps or gelcaps, are composed of gelatin manufactured from the collagen of animal skin or bone.[4]
Vegetable capsules, introduced in 1989,[5] are made from cellulose, a structural component in plants. The main ingredient of vegetarian capsules is hydroxypropyl methyl cellulose. In the 21st century, gelatin capsules are more broadly used than vegetarian capsules because the cost of production is lower.[citation needed]
Manufacturing equipment
[edit]The process of encapsulation of hard gelatin capsules can be done on manual, semi-automatic, and automatic capsule filling machines. Hard gelatin capsules are manufactured by the dipping method which is dipping, rotation, drying, stripping, trimming, and joining.[6] Softgels are filled at the same time as they are produced and sealed on the rotary die of a fully automatic machine. Capsule fill weight is a critical attribute in encapsulation and various real-time fill weight monitoring techniques such as near-infrared spectroscopy (NIR) and vibrational spectroscopy are used, as well as in-line weight checks, to ensure product quality.[7]
Volume is measured to the full line, which is customary to the top of the smaller-diameter body half.[citation needed] After capping, some ullage volume (airspace) remains in the finished capsule.
Standard sizes of two-piece capsules
[edit]| Size | Volume (mL)[A] | Locked length (mm)[A] | External diameter (mm)[A] |
|---|---|---|---|
| 5 | 0.13 | 11.1 | 4.91 |
| 4 | 0.20 | 14.3 | 5.31 |
| 3 | 0.27 | 15.9 | 5.82 |
| 2 | 0.37 | 18 | 6.35 |
| 1 | 0.48 | 19.4 | 6.91 |
| 0 | 0.67 | 21.7 | 7.65 |
| 0E | 0.7 | 23.1 | 7.65 |
| 00 | 0.95 | 23.3 | 8.53 |
| 000 | 1.36 | 26.14 | 9.91 |
| 13 | 3.2 | 30 | 15.3 |
| 12 | 5 | 40.5 | 15.3 |
| 12el | 7.5 | 57 | 15.5 |
| 11 | 10 | 47.5 | 20.9 |
| 10 | 18 | 64 | 23.4 |
| 7 | 24 | 78 | 23.4 |
| Su07 | 28 | 88.5 | 23.4 |
| A Approximate |
See also
[edit]References
[edit]- ^ Safire, William (March 9, 1986). "On Language; The Caplet Solution". The New York Times. Retrieved December 6, 2017.
- ^ "History of dosage forms and basic preparations". Encyclopedia of Pharmaceutical Technology. Vol. 7. Informa Health Care. 1998. pp. 304–306. ISBN 0-8247-2806-8.
- ^ Bill Bennett; Graham Cole (2003). Pharmaceutical Production, an Engineering Guide. IChemE. pp. 126–129. ISBN 0-85295-440-9.
- ^ Prakash, A.; Soni, H.; Mishra, A.; Sarma, P. (2017). "Are your capsules vegetarian or nonvegetarian: An ethical and scientific justification". Indian Journal of Pharmacology. 49 (5): 401–404. doi:10.4103/ijp.IJP_409_17. PMC 5830853. PMID 29515283.
- ^ Tatham KC, Patel KP (2014). "Why can't all drugs be vegetarian?" (PDF). BMJ. 348: g401. doi:10.1136/bmj.g401. PMID 24496281. S2CID 42628750.
- ^ Bhakar, Naresh (December 28, 2020). "Capsules, Types, and formulation (Complete guide) » Pharmaguddu". Pharmaguddu.
- ^ "Pharmaceutical Encapsulation". PharmaCMC. Archived from the original on October 6, 2016. Retrieved September 27, 2016.
- L. Lachman; H.A. Lieberman; J.L. Kanig (1986). The Theory and Practice of Industrial Pharmacy (Third ed.). Lea & Febiger, Philadelphia. ISBN 0-8121-0977-5.
- US Patent 8728521, Hemant N. Joshi, issued May 20, 2014
- US Patent 9884024, Hemant N. Joshi, issued February 6, 2018
- US Patent 10357461, Hemant N. Joshi, issued July 23, 2019
- Sant, Harshada (April 2018). ""Joshi Capsules" US patent numbers – 8728521 and 9884024". American Pharmaceutical Review: 60.
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Capsule (pharmacy)
View on Grokipediafrom Grokipedia
Overview
Definition and Purpose
A capsule is a solid oral dosage form in which one or more medicinal substances are enclosed within a soluble shell, typically available in hard or soft varieties.[7] The primary purposes of capsules include masking unpleasant tastes, odors, or appearances of the enclosed medication, protecting sensitive drugs from environmental factors such as moisture or light, enabling controlled release profiles for sustained or targeted delivery, and facilitating ease of swallowing for patients who may struggle with other forms.[4][8] Capsules offer several advantages, such as precise unit dosing, compatibility with a range of fill materials including powders, liquids, and semi-solids, and cost-effectiveness for small-batch production since they require no compression machinery. Compared to tablets, capsules generally dissolve more rapidly in the stomach, leading to quicker absorption, and avoid the need for compression which can degrade certain active ingredients.[4][9]Historical Development
The development of pharmaceutical capsules began in the early 19th century as pharmacists sought reliable methods to enclose bitter or unpleasant-tasting medicines. In 1833, French pharmacists Joseph Dublanc and François Mothes patented the first single-piece soft gelatin capsule, formed by dipping molds into a gelatin solution and sealing it with a drop of gelatin, marking an initial effort to create hermetic enclosures for liquid or semi-solid formulations.[10][11] This innovation laid the groundwork for soft capsules, though early production was labor-intensive and limited to small scales. Hard gelatin capsules emerged shortly thereafter, with London inventor James Murdock patenting the first two-piece telescoping design in 1847, which consisted of a body and cap formed by dipping metal pins into gelatin and allowing it to dry.[12][13] This structure facilitated easier filling with powders or granules and became the dominant form for solid-dose pharmaceuticals. Key advancements followed in the late 19th and early 20th centuries; Eli Lilly & Company introduced the first automated production line for hard gelatin capsules in 1913, enabling mass manufacturing.[12] Concurrently, the shift to machine filling accelerated around this period, with semi-automatic devices like the Model No. 8 machine emerging to handle industrial-scale powder dosing, reducing manual labor and improving consistency.[14][15] Soft capsule technology advanced significantly in the 1930s through Robert Pauli Scherer's invention of the rotary die encapsulation machine in 1933, which automated the forming, filling, and sealing process, making commercial production viable for pharmaceuticals such as vitamin E formulations derived from wheat germ oil, first marketed in capsules by Glaxo Laboratories in 1933.[16][11][17] World War II disrupted gelatin supplies, as the material was diverted for medical uses like plasma substitutes, prompting postwar shortages that influenced capsule manufacturing and spurred innovations in supply chains.[18][19] By the 1990s, concerns over bovine spongiform encephalopathy (BSE) and demands from religious, vegetarian, and vegan consumers drove the development of non-gelatin alternatives, such as hydroxypropyl methylcellulose (HPMC)-based hard capsules, which entered mainstream production around the mid-1990s to provide animal-free options without compromising functionality. In the 21st century, further innovations include pullulan- and starch-based capsules for improved sustainability and reduced environmental impact, as of 2025.[20][21][22] These milestones reflect capsules' evolution from artisanal enclosures to versatile, scalable dosage forms essential in modern pharmacy.Types
Hard Capsules
Hard capsules consist of two telescoping pieces—a longer body and a shorter cap—that fit together to form a sealed enclosure for pharmaceutical formulations. These shells are manufactured by dipping pairs of stainless steel pins into a controlled-temperature gelatin solution, where the gelatin adheres and dries to form the capsule halves; the pins are then cooled, trimmed, and the empty capsules are separated from the molds. This process results in rigid, pre-formed containers typically supplied empty to pharmaceutical manufacturers for subsequent filling with powders, granules, or compatible liquid and semi-solid formulations.[23][24][25][26] The rigid structure of hard capsules arises from their firm gelatin walls, making them ideal for non-flowable solid fills that require protection from environmental factors without the need for additional sealing beyond the telescoping fit. To ensure integrity, they incorporate locking mechanisms such as interlocking grooves on the body and cap or advanced features like notches and SNAP-FIT designs that prevent accidental separation during transport or handling. However, their gelatin-based composition renders them highly moisture-sensitive, with shells containing 13–16% water; low humidity can cause brittleness and cracking, while excess moisture may lead to softening or deformation, necessitating controlled storage conditions.[27][28][29][5] In pharmaceutical applications, hard capsules are commonly employed for immediate-release dosage forms, including antibiotics such as minocycline hydrochloride and nutraceuticals like vitamins and minerals, where they mask unpleasant tastes and odors while enabling rapid disintegration in the gastrointestinal tract. Their design supports fill weights typically ranging from 0.05 g in smaller sizes (e.g., size 5) to approximately 1 g in larger sizes (e.g., size 000), accommodating a variety of powder-based formulations. Compared to soft capsules, hard capsules lack a hermetic seam, facilitating easier opening for content inspection or tampering verification, and their production occurs in larger batches due to the straightforward dry-filling processes. Shell materials, primarily gelatin, are discussed in detail in the Materials section.[29][30][23][31][5]Soft Capsules
Soft gelatin capsules, also known as softgels, consist of a hermetically sealed, one-piece shell that encloses oils, suspensions, or semi-solids, providing a tamper-evident and airtight container for the active ingredients.[32] The shell is formed through a rotary die encapsulation process, where molten gelatin is extruded into ribbons that are fed between two synchronized rotating dies; these dies simultaneously shape the capsule, inject the fill material, and seal the edges by heat and pressure in a continuous, single-step operation.[33] These capsules exhibit flexibility due to their gelatin-based construction, allowing them to withstand compression without breaking, and they can be manufactured as transparent for visual inspection of contents or opaque to shield sensitive fills from light exposure.[32] With a moisture content typically ranging from 6% to 13%, soft capsules maintain pliability while offering enhanced protection against oxygen permeation compared to other dosage forms, making them suitable for oxidation-prone compounds.[34] Soft capsules are particularly advantageous for encapsulating low-dose liquid or semi-solid formulations, such as vitamins, hormones, or essential oils, where uniform distribution and stability are critical.[35] Representative applications include fish oil supplements, which benefit from the shell's barrier properties to prevent rancidity, and ibuprofen suspensions for improved patient compliance through taste masking and ease of swallowing.[36] The fill compositions compatible with these capsules, including non-aqueous solvents and gelling agents, are addressed in the Materials section.Materials
Shell Composition
The shells of pharmaceutical capsules are predominantly composed of gelatin for both hard and soft varieties, derived from animal collagen through controlled hydrolysis processes. Type A gelatin is produced via acid processing, typically from porcine skins, resulting in a material with an isoelectric point around pH 9 and high clarity. Type B gelatin, obtained through alkaline processing of bovine bones or hides, has an isoelectric point near pH 5 and is more commonly used due to its availability and cost-effectiveness. In hard gelatin capsules, the dried shell typically comprises 86–90% gelatin by weight, with 13–16% water serving as the primary plasticizer to maintain flexibility and prevent brittleness. Soft gelatin capsules, in contrast, feature a formulation with 40–50% gelatin (primarily protein content), 20–30% non-volatile plasticizers such as glycerin or sorbitol to enhance pliability, and 4–10% residual moisture after drying.[37][38][39] Non-gelatin alternatives have gained prominence to address dietary restrictions, religious concerns, and allergen sensitivities, with hydroxypropyl methylcellulose (HPMC) being the most widely adopted plant-based option for vegetarian and vegan applications. HPMC shells are formulated from purified cellulose derivatives, typically including 70–90% HPMC polymer, along with water, plasticizers like polyethylene glycol, and gelling agents such as carrageenan or gellan gum to achieve the necessary film-forming properties. These shells offer superior stability in low-humidity conditions (moisture content 4–8%) and reduced risk of cross-linking with aldehydes in fills, but they can exhibit slower dissolution rates—often 5–10 minutes longer than gelatin in acidic media—potentially delaying drug release, though this is rarely clinically significant. Starch-based shells, derived from sources like potato or modified corn starch, provide hypoallergenic profiles and good barrier properties against moisture and oxygen, with compositions centered on 60–80% starch, water, and plasticizers; they are ideal for sensitive actives but may require higher processing temperatures. Pullulan capsules, produced via fungal fermentation of Aureobasidium pullulans, consist mainly of the polysaccharide (80–95%) with minimal additives, excelling in oxygen impermeability (up to 250 times better than HPMC) and hypoallergenic suitability, though they are more costly and less mechanically robust.[5][40][41] Additives are incorporated into capsule shells to improve aesthetics, functionality, and stability while adhering to strict regulatory standards. Common colorants include certified FD&C dyes (e.g., Blue No. 1, Red No. 40) for water-soluble tinting and iron oxides for opaque pigmentation, applied at levels below 2% to avoid impacting dissolution. Titanium dioxide serves as an opacifier and white pigment, limited to no more than 1% in finished products per FDA guidelines to ensure safety and light protection for light-sensitive fills; however, as of 2025, TiO2 faces ongoing safety reviews with bans in EU food products since 2022 and petitions for restrictions in US pharmaceuticals due to genotoxicity concerns.[42][43][44] Preservatives like methylparaben are occasionally added at trace levels (<0.2%) in soft shells to prevent microbial growth, though they are generally omitted in hard capsules under good manufacturing practices. Regulatory limits on heavy metals in gelatin, per the USP Gelatin monograph, restrict total heavy metals to not more than 50 ppm and arsenic to not more than 0.8 ppm to mitigate contamination risks from raw materials.[45] Key stability factors for gelatin shells include Bloom strength, a measure of gel rigidity determined by the force required to depress a plunger into a 6.67% gelatin gel, with pharmaceutical-grade material typically ranging from 150–250 Bloom units to balance hardness and solubility—higher values (200–250) are preferred for hard capsules to withstand mechanical stress during filling. Gelatin shells demonstrate pH compatibility in the range of 2.5–7.5 for fill formulations, beyond which hydrolysis or precipitation may occur, compromising shell integrity; optimal performance is observed at pH 4–6 for most oral applications. Non-gelatin shells like HPMC exhibit broader pH tolerance (1–14) and lower moisture sensitivity, enhancing their suitability for hygroscopic or acidic fills.[37][39][46]Fill Composition
The fill composition of hard capsules typically consists of dry powders or granules that include the active pharmaceutical ingredient (API) blended with excipients to ensure proper flow, compressibility, and content uniformity during encapsulation. Common excipients include diluents such as lactose or microcrystalline cellulose to bulk up the formulation and improve powder flow, and lubricants like magnesium stearate at concentrations of 0.25–2% to reduce friction and prevent sticking to machinery.[47][5] Other additives, such as glidants (e.g., colloidal silicon dioxide) at 0.1–1%, enhance powder mobility, while disintegrants like croscarmellose sodium (1–5%) promote rapid breakdown in gastrointestinal fluids for efficient drug release.[48] In contrast, soft capsules are filled with liquids or semi-solids, often comprising oils, polyethylene glycol (PEG) solvents, or suspensions to solubilize or suspend the API. Lipophilic fills, such as vegetable oils or medium-chain triglycerides, are common for poorly water-soluble drugs, while hydrophilic fills using PEG 400 or 600 provide better compatibility for water-soluble actives.[26] The viscosity of these fills must be suitable for the rotary die process, typically below 50,000 cps at filling temperatures of 35–50°C, to ensure smooth injection into the gelatin ribbon, seal integrity, and prevent leakage.[26] Formulation considerations for capsule fills emphasize compatibility with the shell material, particularly for gelatin-based capsules, where high-humidity or hygroscopic fills can lead to moisture migration, softening the shell, or cross-linking that delays dissolution.[26] Dose uniformity is achieved through uniform blending and particle size control, with regulatory standards requiring relative standard deviation below 6% for low-dose APIs to ensure consistent drug delivery.[49] Disintegration aids, such as croscarmellose sodium in hard capsule powders, are selected to swell upon contact with fluids, aiding rapid API release without compromising stability.[50] Special fill types include modified-release beads or pellets encapsulated in hard shells for sustained or controlled drug action; these multiparticulate systems, often coated with polymers like ethylcellulose, provide even distribution in the gastrointestinal tract, reducing peak-trough fluctuations in plasma levels compared to single-unit dosage forms.[51][52]Manufacturing
Production Equipment
The production of hard gelatin capsules begins with specialized equipment for shell formation, including gelatin dipping tanks where preheated gelatin solutions are maintained at controlled temperatures and viscosities before being dipped onto stainless steel pins arranged on rotating plates. These pins, typically cooled to around 20–25°C, are immersed into the gelatin bath to form uniform shell layers, with multiple dipping cycles used to achieve the desired thickness of 100–200 micrometers per shell half. Following dipping, the pins enter drying kilns or multi-zone drying tunnels, where forced hot air (at 30–50°C) circulates to gradually dry the shells over 4–8 hours, preventing defects like brittleness or adhesion. Rectifying machines, often integrated into filling lines, use vibratory or roller systems to orient and separate capsule bodies from caps, achieving up to 99% accuracy in alignment for subsequent filling.[53][54][55] Automatic filling machines for hard capsules, such as MG2's Planeta and G-series models or Bosch's GKF series, employ dosator systems to measure and dispense powder fills volumetrically. In the dosator mechanism, a rotating dosing disc with hollow nozzles draws powder from a hopper, compresses it into a metered plug using a spring-loaded piston, and ejects it into the capsule body, allowing precise control over fill weights as low as 5–45 mg with variability under 2%. These machines operate at speeds ranging from 6,000 to 250,000 capsules per hour, depending on the model, and incorporate vacuum-assisted powder beds for consistent density in free-flowing or cohesive formulations.[56][57][58] Soft capsule production relies on rotary die machines, exemplified by systems like the Scherer KS series, which form gelatin ribbons from heated gel sheets fed through wedge-shaped distributors to ensure even thickness of 0.3–0.5 mm. The ribbons converge at a filling wedge where liquid or semi-solid fills are injected, and synchronized rotating dies seal and cut the capsules in a continuous rotary motion, producing oblong, round, or custom shapes with fill volumes of 0.2–2 mL. Encapsulation speeds on these machines can reach up to 100,000 capsules per hour, with die roll diameters of 150–250 mm enabling high throughput while minimizing waste through precise synchronization.[59][60][61] Auxiliary equipment supports the overall process, including mixing blenders such as V-blenders or ribbon mixers that homogenize powder or granular fills to achieve uniformity within 5% relative standard deviation before transfer to filling hoppers. Capsule polishers, often using rotating nylon brushes and vacuum extraction, remove residual powder and oils post-filling, achieving surface cleanliness compliant with USP standards. Inspection stations, equipped with high-speed cameras or laser sensors, detect defects like cracks, incomplete fills, or foreign particles at rates up to 300,000 units per hour, rejecting non-conforming capsules via pneumatic ejection.[62][63][64] Production scales vary from lab-scale manual fillers, which handle 100–3,000 capsules per batch for R&D and small runs with minimal automation, to industrial high-speed lines capable of 100,000–400,000 capsules per hour for commercial manufacturing. Rotary die machines for soft capsules typically require 20–30 kW of power for operations involving heating, pumping, and die rotation, while larger hard capsule lines may consume up to 50 kW, incorporating energy-efficient features like variable frequency drives to optimize consumption.[65][66][58]Encapsulation Processes
The encapsulation process for hard capsules begins with shell formation, where preheated stainless steel pins or molds are dipped into a warm gelatin solution to coat them evenly, followed by spinning to remove excess solution and controlled drying in temperature- and humidity-regulated chambers to form the cap and body halves.[67] The dried shells are then stripped from the pins, trimmed to precise lengths, and temporarily joined for storage or transport until filling.[67] Once ready for filling, the joined capsules are separated into caps and bodies on automated machines, with the bodies dosed using either tamping (where powder is compressed into multiple slugs via pins and transferred) or dosing disc methods (where powder is volumetrically metered into the body).[68][69] The filled bodies are rejoined with the caps, and the assembled capsules undergo polishing with soft brushes or cloths to remove any adhering powder residue.[69] For soft capsules, the process starts with gel preparation, involving the mixing of gelatin with water and plasticizers in a heated kettle to form a viscous mass at around 50-60°C, which is then deaerated to eliminate air bubbles.[39] This gel is extruded onto cooled rotating drums to form two continuous ribbons of uniform thickness, which are fed between synchronized rotary dies preheated to 37-40°C.[39] The fill material—typically a liquid, semisolid, or suspension—is injected between the ribbons via syringes or pumps as the dies rotate, simultaneously forming pockets, sealing the edges through heat and pressure from the dies, and cutting the individual capsules.[39] The resulting soft capsules are collected, washed to remove excess gelatin, and dried in tumbling drums under controlled airflow for several hours until they reach equilibrium moisture content.[69] Quality control during encapsulation includes in-process weight checks on sampled capsules to ensure fill uniformity, with automated checkweighers rejecting those exceeding specified variation limits (typically ±7.5% for average weight).[70] Leak testing for soft capsules involves visual inspection for defects or submersion in dye solutions to detect breaches, while hard capsules are examined for cap-body separation or cracks.[71] Environmental controls are critical, particularly for gelatin-based capsules, maintaining room temperatures of 20-25°C and relative humidity of 40-60% to prevent shell softening, brittleness, or microbial growth.[72] Variations in encapsulation include manual methods for small-scale or R&D batches, where operators hand-separate, fill, and join capsules using plates or simple tools, offering flexibility but lower precision and throughput compared to automated systems that achieve rates up to 200,000 capsules per hour with integrated dosing and quality checks.[49] For hygroscopic fills prone to moisture absorption, dehumidifiers maintain low humidity levels (below 30% RH in filling areas) to ensure powder flowability and prevent clumping during dosing.[73]Sizes and Standards
Standard Dimensions
Standard two-piece hard capsules in pharmacy are designated by a numerical sizing system that inversely corresponds to their volume capacity, ranging from size 000 (the largest, approximately 1.37 mL) to size 5 (the smallest, approximately 0.13 mL). This system allows for consistent dosing across formulations, with external diameters typically spanning 6.4 mm to 12.2 mm and locked lengths from 11 mm to 26 mm, enabling compatibility with filling equipment and patient swallowability.[74][75] The following table summarizes key dimensions for common sizes, based on industry specifications from leading manufacturers:| Size | Volume (mL) | Locked Length (mm) | Cap Diameter (mm) | Body Diameter (mm) |
|---|---|---|---|---|
| 000 | 1.37 | 26.1 ± 0.5 | 12.2 | 11.8 |
| 00 | 0.95 | 23.3 ± 0.5 | 11.8 | 11.4 |
| 0 | 0.68 | 21.7 ± 0.5 | 11.0 | 10.7 |
| 1 | 0.50 | 19.4 ± 0.5 | 9.9 | 9.6 |
| 2 | 0.37 | 17.6 ± 0.5 | 8.9 | 8.6 |
| 3 | 0.30 | 15.9 ± 0.5 | 8.2 | 7.9 |
| 4 | 0.21 | 14.3 ± 0.5 | 7.5 | 7.2 |
| 5 | 0.13 | 11.1 ± 0.5 | 6.4 | 6.1 |