by egpat 28 May 2024
Alfuzosin is an alpha-1 blocker. We have a few other drugs like prazosin, doxazosin, and terazosin, all of which end with the same suffix, -zosin, which indicates they belong to the category of alpha-1 blockers. Another drug, tamsulosin, has a similar suffix, and it is somewhat more selective towards the alpha-1 subtype A receptors. These alpha-1A receptors are located on the bladder as well as the prostate tissue. Likewise, alfuzosin is also selective for alpha-1A receptors. That's why alfuzosin can be used in the treatment of benign prostatic hyperplasia. However, it can also block other types of alpha-1 receptors.
Alfuzosin can block the alpha-1 receptors located at the bladder base, neck, prostate capsule, and urethra. By blocking the alpha-1 receptors at these target organs, alfuzosin can produce bladder relaxation, which may increase the urinary flow. In BPH, urinary flow is going to be reduced because of prostate enlargement and subsequent narrowing of the urethral pathway. Alfuzosin can produce relaxation, thereby increasing the urinary flow.
Similarly, alfuzosin also blocks the alpha-1 receptors located in the other organs, particularly the vascular smooth muscle. This results in hypotension, which may lead to syncope and fainting.
At the target organs, like the bladder or vascular smooth muscle, alpha-1 receptors are present, which are G-protein-coupled receptors with seven transmembrane units. These alpha-1 receptors can be activated by one of the important mediators, norepinephrine. Norepinephrine is the sympathetic mediator; when it acts on the alpha-1 receptors, it can produce the contraction. This norepinephrine can bind to these alpha receptors, which are G-protein-coupled receptors coupled with the phospholipase C system. So by stimulating these receptors, phospholipase C is going to be activated, which can cleave the phosphatidyl inositol biphosphate into the two important components. One is the IP 3, and the second is the DAG, diacyl glycerol. This IP3 can act on the internal stores that store calcium. IP3, which is released as a secondary messenger, can act on the IP3 receptors located on these internal calcium stores. This results in the release of calcium from the sarcoplasmic reticulum.
Diacyl glycerol can activate the protein kinase G, which is going to stimulate the inward-going calcium channels. Now calcium can more easily enter the cell, so the intracellular calcium levels are going to increase. Whenever these intracellular calcium levels are increased, they produce the contraction of the smooth muscle. In this way, norepinephrine can produce contractions in the bladder base, neck, prostate capsule, urethra, and vascular smooth muscle.
Alfuzosin acts as an antagonist at the alpha-1 receptors, thereby preventing the contraction of the smooth muscle. In this way, alfuzosin can produce bladder relaxation as well as vasodilation.
The important side effects include headache, dizziness, and fatigue, and particularly these three symptoms are closely associated with the vasodilatory effects that can be produced by alfuzosin. Similarly, alfuzosin can also produce a few upper respiratory tract infections. This drug is reported to produce bronchitis and pharyngitis, so these symptoms should be carefully monitored when this alfuzosin is used for longer periods.
Another important side effect is postural hypotension. Due to its alpha-1 block activity, it can produce vasodilation, resulting in postural hypotension. Other side effects include constipation, dyspepsia, and nausea. It can also produce some chest pain. That's why this drug should be carefully given to patients with preexisting cardiovascular complications.
Alfuzosin can produce priapism, the long-term erection of the erectile tissue, which may produce some pain. Because of the vasodilation, edema is also observed with alfuzosin. Here is a video explaining the mechanism, precautions, and side effects of alfuzosin.
As alfuzosin blocks the alpha-1 receptors, it can produce postural hypotension. Therefore, it can produce a few of the symptoms, like dizziness, blurred vision, syncope, fainting, weakness, and confusion. Therefore, these symptoms should be carefully monitored while using alfuzosin. Interestingly, these symptoms can be observed even with the first dose of alfuzosin. That's why these symptoms are called first-dose effects.
Another important precaution is that alfuzosin can cause renal impairment, so it should be carefully given to renally impaired patients. On long-term use, alfuzosin can reduce hepatic function. Therefore, for people with severe hepatic impairment, this drug should be strictly contraindicated.
Alfuzosin is available as an oral tablet. This is an extended-release tablet that delivers the medication slowly into the body for an extended period of time. To preserve its long-term action and to avoid the sudden release of medication, this tablet should not be crushed or broken. The correct dose of alfuzosin depends on the conditions of the patient and other medications co-administered. For benign prostatic hyperplasia, this drug is typically given at a dose of 10 mg once daily.
Alfuzosin is one of the alpha-1 blockers that has a quinazoline-4-amine moiety. This drug acts as an antagonist on alpha-1 receptors as well as alpha-1A receptors. That's why this drug is indicated for the treatment of benign prostatic hyperplasia. As this drug produces bladder relaxation and increases urinary flow, it can be used in the treatment of BPH, but at the same time it produces vasodilation, which may result in postural hypotension, resulting in dizziness and syncope in the patients. This drug is available as an extended-release tablet, which is given at a dose of 10 mg once daily.