Overview Of Sildenafil Troche
Dosage Power Of Sildenafil Troche
Generic Details
Sildenafil citrate is a vasoactive medication belonging to the drug class of phosphodiesterase – 5 enzyme (PDE-5) inhibitors; it is a competitive antagonist of this enzyme. PDE-5 can be found all over the human body especially in the corpus cavernosum within the penis, striated and smooth musculature, as well as in platelets. However, PDE-5 has the largest distribution in the penile corpus cavernosum which is why sildenafil citrate is able to work selectively in this part of the body.
Sildenafil citrate is generally administered orally. However, it can also be administered intravenously or sublingually. Even though its most popular clinical indication for use is in the management of erectile dysfunction, it is also used in the management of pulmonary hypertension, persistent pulmonary hypertension of the newborn, Raynaud’s phenomenon resistant to other vasodilators, as well as in the prevention of pulmonary edema at high altitudes. After oral ingestion, absorption of sildenafil citrate rapidly occurs mainly in the small intestine from where it is then transported in the bloodstream to its area of action. Sildenafil citrate is metabolized in the liver through the action of the hepatic isoenzymes cytochrome P450 3A4 and cytochrome P450 2C9. Following hepatic metabolism, the metabolites are excreted mainly in the stool and, to a lesser degree, in the urine.
Sildenafil citrate is classified as a pregnancy category B drug by the Food and Drug Administration. Studies have not demonstrated definite risks to fetuses when sildenafil is administered to pregnant mothers. At present, there are no definite clinical indications that warrant the administration of sildenafil citrate in women. Studies done till date have not indicated that sildenafil citrate has comparable benefits in women as they do in men. There are other studies that are still ongoing, however, and their outcomes may provide further insight regarding the utility and benefits of sildenafil in women.
MOA
Clinical Pharmacokinetics
Metabolism of sildenafil citrate occurs primarily in the liver through the action of the hepatic microsomal isoenzymes cytochrome P450 3A4 and 2C9. After the action of the isoenzymes on sildenafil, it is broken down into an N-desmethyl metabolite. Both sildenafil citrate as well as its N-desmethyl metabolite breakdown product are tightly bound to plasma proteins and they have an approximate half-life of four hours. it is estimated that about 96 percent of sildenafil and its metabolite are bound to plasma proteins after oral ingestion. Following its metabolism, the majority of sildenafil citrate is excreted in the stool; a lesser amount, about 13 percent of sildenafil metabolites, is excreted in the urine.
There are a number of factors that can interfere with the metabolism of sildenafil, thereby increasing or decreasing its concentration in the body. Some of these factors include the following:
Hepatic impairment: Individuals who have significant hepatic disease such as liver cirrhosis may experience a significant increase in plasma sildenafil levels. This is because the production of the hepatic isoenzymes cytochrome P450 3A4 and 2C9 are markedly diminished in liver cirrhosis. As a result of this diminished production of the hepatic isoenzymes, the body is not able to adequately metabolize sildenafil citrate, resulting in increased plasma levels.
Renal impairment: Individuals with significant renal disease as evidenced with a creatinine clearance of less than 30mL/min will have a marked increase in plasma sildenafil levels after oral ingestion. Since sildenafil and its metabolites are excreted through the kidneys, renal diseases will impair the ability of the kidneys to perform this task adequately.
Age: For reasons that are yet to be fully determined, there is a 40 percent increase in the plasma levels of sildenafil and its N-desmethyl metabolite when administered to men greater than 65 years of age.
Cytochrome P450 3A4 inhibitors: The concomitant use of drugs known to inhibit the hepatic cytochrome P450 enzymes may result in increased plasma levels of sildenafil. Examples of drugs that are known P450 inhibitors are macrolide antibiotics such as erythromycin, antifungal agents such as ketoconazole, and protease inhibitors such as indinavir. By inhibiting the production of cytochrome P450, hepatic metabolism of sildenafil does not occur, leading to its increased levels in plasma.
Precautions
Hypersensitivity: Sildenafil is absolutely contraindicated in individuals who have a demonstrated hypersensitivity to the drug or any of its components.
Nitrate therapy: Individuals who are not nitrate therapy should not be administered sildenafil citrate. Nitrates are potent vasodilators typically used in the management of cardiac conditions such as angina pectoris. Since sildenafil also a vasodilatory effect through its actions on cGMP, it can potentiate the effects of nitrates when used concurrently which may result in severe hypotension, syncope, and myocardial infarction.
Hepatic disease: Since sildenafil is metabolized by hepatic isozymes, hepatic diseases may lead to increased plasma levels of sildenafil and a prolongation of its effects. Care should be exercised when administering sildenafil to individuals with hepatic disease.
Renal disease: Similar to hepatic diseases, renal diseases may prolong the effects of sildenafil citrate due to increased plasma levels as a result of diminished renal excretion. Caution should also be exercised when administering sildenafil to individuals with renal diseases.
Visual abnormalities: There have been some instances of vision loss in individuals taking sildenafil citrate. The loss of vision is due to a reduction in blood flow to the optic nerve, a condition known as non-arteritic anterior ischemic optic neuropathy (NAION). Individuals with pre-existing visual disturbances may be administered sildenafil only when the benefits clearly outweigh the risks.
Cardiovascular disorders: Caution should be exercised when administering sildenafil to individuals with known cardiac disorders such as arrhythmias, aortic stenosis, heart failure, and myocardial infarction, among others.
Pregnancy
Breast-Feeding
Slidenafil Troche Side Effects & Reactions
How To Store
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