Informational only — Not medical advice. Always consult a licensed healthcare provider.

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Community data Updated 23 hours ago
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Indications

Hypertension Erectile Dysfunction

Sildenafil Citrate is used to treat men with erectile dysfunction, which means being unable to get or keep an erection firm enough for satisfactory sexual performance. The medicine only works when there is sexual stimulation. Sildenafil Citrate is also used for pulmonary arterial hypertension.

⚠️ Always consult a registered physician before taking any medicine.

Pharmacology

Mechanism of Action

Erection of the penis depends on the release of nitric oxide (NO) in the corpus cavernosum during sexual stimulation. NO activates the enzyme guanylate cyclase, which raises the level of cyclic guanosine monophosphate (cGMP). This relaxes the smooth muscle in the corpus cavernosum and lets blood flow in. Sildenafil has no direct relaxant effect on isolated human corpus cavernosum. Instead, it strengthens the effect of NO by inhibiting phosphodiesterase type 5 (PDE5), the enzyme that breaks down cGMP in the corpus cavernosum. So when sexual stimulation releases NO locally, the inhibition of PDE5 by Sildenafil lets cGMP rise, the smooth muscle relaxes and blood flows into the corpus cavernosum. At the recommended doses, Sildenafil has no effect without sexual stimulation.

Pharmacokinetics and Metabolism

Sildenafil is absorbed rapidly after oral dosing, with a mean absolute bioavailability of 41% (range 25 to 63%). It is removed mainly by hepatic metabolism (mainly cytochrome P450 3A4) and is converted to an active metabolite with properties similar to Sildenafil itself. Both Sildenafil and the metabolite have terminal half lives of about 4 hours.

Absorption and Distribution

Maximum observed plasma concentrations are reached within 30 to 120 minutes (median 60 minutes) of oral dosing in the fasted state. If Sildenafil is taken with a high fat meal, the rate of absorption is reduced.

Metabolism and Excretion

Hepatic microsomal isoenzymes clear Sildenafil from the body. After oral or intravenous dosing, it leaves as metabolites, mostly in the feces (approximately 80% of the oral dose) and to a lesser extent in the urine (approximately 13% of the oral dose).

Pharmacokinetics in Special Populations

Geriatrics: Healthy elderly volunteers (65 years or over) cleared Sildenafil more slowly. Their plasma AUC values were approximately 84% and 107% higher than those seen in healthy younger volunteers.

Pregnancy & Breastfeeding

Sildenafil is pregnancy category B. No adequate and well-controlled studies of Sildenafil have been done in pregnant women, and the medicine is not indicated for use by women. In animal studies, Sildenafil showed no evidence of teratogenicity or embryotoxicity.

⚠️ Talk to your doctor before taking any medicine during pregnancy or while breastfeeding.

Dosage Reference

⚠️ Reference ranges from official sources only. Consult your doctor for personalized dosing.

Adults: Erectile dysfunction: For most patients, the recommended dose of Sildenafil is 50 mg, taken as needed about 1 hour before sexual activity. It can be taken anywhere from 4 hours to 0.5 hour before. Depending on how well it works and how well the patient tolerates it, the dose may be raised to a maximum of 100 mg or lowered to 25 mg. It should not be taken more than once per day. Some factors are linked with higher plasma levels of Sildenafil: age over 65, hepatic impairment, severe renal impairment, and use together with potent cytochrome P450 3A4 inhibitors (ketoconazole, itraconazole, erythromycin, saquinavir). Higher plasma levels may increase both the effect and the number of adverse events, so a starting dose of 25 mg should be considered in these patients. Sildenafil was shown to increase the blood pressure lowering effect of nitrates. For this reason, it is contraindicated in patients who use nitric oxide donors or nitrates in any form. When Sildenafil is given with an alpha-blocker, the patient should be stable on the alpha-blocker before Sildenafil is started, and Sildenafil should be started at the lowest dose. Pulmonary arterial hypertension: The recommended dose of sildenafil citrate is 20 mg three times a day, taken about 4 to 6 hours apart, with or without food.

Side Effects & Interactions

Side Effects

No side-effect data recorded yet.