Recent from talks
Alpha-1 blocker
Knowledge base stats:
Talk channels stats:
Members stats:
Alpha-1 blocker
Alpha-1 blockers (also called alpha-adrenergic blocking agents or alpha-1 antagonists) constitute a variety of drugs that block the effect of catecholamines on alpha-1-adrenergic receptors. They are mainly used to treat benign prostatic hyperplasia (BPH), hypertension and post-traumatic stress disorder. Alpha-1-adrenergic receptors are present in vascular smooth muscle, the central nervous system, and other tissues. When alpha blockers bind to these receptors in vascular smooth muscle, they cause vasodilation.
Over the last 40 years, a variety of drugs have been developed from non-selective alpha-1 receptor antagonists to selective alpha-1 antagonists and alpha-1 receptor inverse agonists. The first drug that was used was a non-selective alpha blocker, named phenoxybenzamine and was used to treat BPH. Currently, several relatively selective alpha-1 antagonists are available. As of 2018, prazosin is the only alpha-1 blocker known to act as an inverse agonist at all alpha-1 adrenergic receptor subtypes; whereas tamsulosin and terazosin are both selective antagonists for all alpha-1 subtypes. Tamsulosin is not centrally active due to poor blood-brain barrier penetration, but terazosin and prazosin are centrally-active. Drugs that act as selective antagonists at specific alpha-1 adrenergic receptor subtypes have also been developed.
Benign prostatic hyperplasia (BPH) is an enlarged prostate gland. Alpha-1 blockers are the most commonly used medicine to treat BPH. Alpha-1 blockers are first line treatment for the symptoms of BPH in men. Doxazosin, terazosin, alfuzosin, and tamsulosin have all been well established in treatment to reduce lower urine tract symptoms (LUTS) caused by benign prostatic hyperplasia. They are all believed to be similarly effective for this purpose. First generation alpha-1 blockers, like prazosin are not recommended to treat lower urinary tract symptoms because of their blood-pressure-lowering effect. Later generation drugs in this class are used for this purpose. In some cases alpha-1 blockers have been used in combined therapy with 5α-reductase inhibitors. Dutasteride and tamsulosin are on the market as combined therapy and results have shown that they improve symptoms significantly versus monotherapy.
Alpha-1 blockers are used as second line treatment for high blood pressure. They are not thought to be good as first line treatment because there are other more selective agents, although they can be good for treating men with hypertension and BPH. Doxazosin has been shown to improve symptoms of BPH in the elderly and reduce blood pressure at the same time. BPH and hypertension are both very common in men over 60 years old.
In patients with neurogenic hypertension who fail in achieving blood pressure control with angiotensin converting enzyme inhibitors (ACEi), Angiotensin receptor blockers (ARB) and calcium channel blockers (CCB), alpha- and beta- adrenergic receptor blockers constitute the main treatment options. This is supported by studies that show surprisingly though consistently that neither alpha- nor beta-blocker mono- therapy reduces sympathetically mediated blood pressure reactivity to acute experimental stressors. Studies of combined oral alpha- and beta-blockade using an alpha-blocker (e.g., doxazosin or terazosin) in combination with a nonlipophilic beta-blocker with more reliable bioavailability (e.g., betaxolol, bisoprolol, atenolol and others) have shown a larger antihypertensive effect. This approach also enables separate titration of alpha- and beta-blocking effects. In these studies, doxazosin was prescribed at the low dose of 1–2 mg.
Post-traumatic stress disorder (PTSD) is a disabling mental condition that can develop following a traumatic experience; for example, it is especially common in military veterans and sexual assault survivors. Prazosin is commonly used as an antihypertensive, but because alpha-1-adrenergic activity has been connected to fear and startle responses, it sees use as a PTSD treatment. Prazosin has been established as an effective and safe centrally active alpha-1-adrenergic receptor antagonist. It can be used to treat trauma-related nightmares, sleep disturbance, and other chronic PTSD symptoms.
As Alpha-1a blockers affect the symptoms of BPH more specifically than non-selective Alpha-1 blockers, the adverse effects seem to be more linked to the reproductive system while minimizing the effect on the blood pressure system. Hypotension and its complications (e.g., weakness, dizziness) are a constant risk, however, even though selective alpha-1a blockers are being used. It is therefore important when starting treatment with an alpha-1 blocker to monitor blood pressure to minimize the risk for adverse effects connected to low blood pressure.[citation needed]
By reducing alpha-1-adrenergic activity of the blood vessels, these drugs may cause hypotension (low blood pressure) and interrupt the baroreflex response. In doing so, they may cause dizziness, lightheadedness, or fainting when rising from a lying or sitting posture (known as orthostatic hypotension or postural hypotension). For this reason, it is generally recommended that alpha blockers should be taken at bedtime. The risk of first dose phenomenon may be reduced or eliminated by gradual-dose titration, since the adverse effects of Prazosin are dose-related. This is also the case for Tamsulosin and it may be assumed that the others alpha-1 blockers work in a similar manner, since Tamsulosin is an alpha-1-a blocker and Prazosin is an alpha-1 blocker. The risk for floppy iris syndrome during cataract surgery is elevated when the patient is using an alpha-1 blocker. This is especially the case for Tamsulosin and other alpha-1-a blockers, since alpha-1-a receptors are present also in the iris dilator muscle, which allows unopposed action of the parasympathetically innervated iris constrictor muscle and loss of iris tone. This however can be treated if the eye surgeon is experienced and has knowledge of the use of alpha-1 blocker.
Hub AI
Alpha-1 blocker AI simulator
(@Alpha-1 blocker_simulator)
Alpha-1 blocker
Alpha-1 blockers (also called alpha-adrenergic blocking agents or alpha-1 antagonists) constitute a variety of drugs that block the effect of catecholamines on alpha-1-adrenergic receptors. They are mainly used to treat benign prostatic hyperplasia (BPH), hypertension and post-traumatic stress disorder. Alpha-1-adrenergic receptors are present in vascular smooth muscle, the central nervous system, and other tissues. When alpha blockers bind to these receptors in vascular smooth muscle, they cause vasodilation.
Over the last 40 years, a variety of drugs have been developed from non-selective alpha-1 receptor antagonists to selective alpha-1 antagonists and alpha-1 receptor inverse agonists. The first drug that was used was a non-selective alpha blocker, named phenoxybenzamine and was used to treat BPH. Currently, several relatively selective alpha-1 antagonists are available. As of 2018, prazosin is the only alpha-1 blocker known to act as an inverse agonist at all alpha-1 adrenergic receptor subtypes; whereas tamsulosin and terazosin are both selective antagonists for all alpha-1 subtypes. Tamsulosin is not centrally active due to poor blood-brain barrier penetration, but terazosin and prazosin are centrally-active. Drugs that act as selective antagonists at specific alpha-1 adrenergic receptor subtypes have also been developed.
Benign prostatic hyperplasia (BPH) is an enlarged prostate gland. Alpha-1 blockers are the most commonly used medicine to treat BPH. Alpha-1 blockers are first line treatment for the symptoms of BPH in men. Doxazosin, terazosin, alfuzosin, and tamsulosin have all been well established in treatment to reduce lower urine tract symptoms (LUTS) caused by benign prostatic hyperplasia. They are all believed to be similarly effective for this purpose. First generation alpha-1 blockers, like prazosin are not recommended to treat lower urinary tract symptoms because of their blood-pressure-lowering effect. Later generation drugs in this class are used for this purpose. In some cases alpha-1 blockers have been used in combined therapy with 5α-reductase inhibitors. Dutasteride and tamsulosin are on the market as combined therapy and results have shown that they improve symptoms significantly versus monotherapy.
Alpha-1 blockers are used as second line treatment for high blood pressure. They are not thought to be good as first line treatment because there are other more selective agents, although they can be good for treating men with hypertension and BPH. Doxazosin has been shown to improve symptoms of BPH in the elderly and reduce blood pressure at the same time. BPH and hypertension are both very common in men over 60 years old.
In patients with neurogenic hypertension who fail in achieving blood pressure control with angiotensin converting enzyme inhibitors (ACEi), Angiotensin receptor blockers (ARB) and calcium channel blockers (CCB), alpha- and beta- adrenergic receptor blockers constitute the main treatment options. This is supported by studies that show surprisingly though consistently that neither alpha- nor beta-blocker mono- therapy reduces sympathetically mediated blood pressure reactivity to acute experimental stressors. Studies of combined oral alpha- and beta-blockade using an alpha-blocker (e.g., doxazosin or terazosin) in combination with a nonlipophilic beta-blocker with more reliable bioavailability (e.g., betaxolol, bisoprolol, atenolol and others) have shown a larger antihypertensive effect. This approach also enables separate titration of alpha- and beta-blocking effects. In these studies, doxazosin was prescribed at the low dose of 1–2 mg.
Post-traumatic stress disorder (PTSD) is a disabling mental condition that can develop following a traumatic experience; for example, it is especially common in military veterans and sexual assault survivors. Prazosin is commonly used as an antihypertensive, but because alpha-1-adrenergic activity has been connected to fear and startle responses, it sees use as a PTSD treatment. Prazosin has been established as an effective and safe centrally active alpha-1-adrenergic receptor antagonist. It can be used to treat trauma-related nightmares, sleep disturbance, and other chronic PTSD symptoms.
As Alpha-1a blockers affect the symptoms of BPH more specifically than non-selective Alpha-1 blockers, the adverse effects seem to be more linked to the reproductive system while minimizing the effect on the blood pressure system. Hypotension and its complications (e.g., weakness, dizziness) are a constant risk, however, even though selective alpha-1a blockers are being used. It is therefore important when starting treatment with an alpha-1 blocker to monitor blood pressure to minimize the risk for adverse effects connected to low blood pressure.[citation needed]
By reducing alpha-1-adrenergic activity of the blood vessels, these drugs may cause hypotension (low blood pressure) and interrupt the baroreflex response. In doing so, they may cause dizziness, lightheadedness, or fainting when rising from a lying or sitting posture (known as orthostatic hypotension or postural hypotension). For this reason, it is generally recommended that alpha blockers should be taken at bedtime. The risk of first dose phenomenon may be reduced or eliminated by gradual-dose titration, since the adverse effects of Prazosin are dose-related. This is also the case for Tamsulosin and it may be assumed that the others alpha-1 blockers work in a similar manner, since Tamsulosin is an alpha-1-a blocker and Prazosin is an alpha-1 blocker. The risk for floppy iris syndrome during cataract surgery is elevated when the patient is using an alpha-1 blocker. This is especially the case for Tamsulosin and other alpha-1-a blockers, since alpha-1-a receptors are present also in the iris dilator muscle, which allows unopposed action of the parasympathetically innervated iris constrictor muscle and loss of iris tone. This however can be treated if the eye surgeon is experienced and has knowledge of the use of alpha-1 blocker.