Description
Sildenafil is a potent and selective inhibitor of the enzyme phosphodiesterase type 5 (PDE5), primarily prescribed for the treatment of erectile dysfunction (ED). By enhancing blood flow to specific tissues, Sildenafil facilitates the achievement and maintenance of an erection sufficient for sexual activity. Its mechanism, while targeted, has also led to its application in treating pulmonary arterial hypertension.
Mechanism of Action
The mechanism of action for Sildenafil centers on its inhibition of PDE5 in the smooth muscle of the corpus cavernosum in the penis. During sexual stimulation, nitric oxide (NO) is released, which activates the enzyme guanylate cyclase. This increases levels of cyclic guanosine monophosphate (cGMP), leading to smooth muscle relaxation and vasodilation, which allows blood to flow into the penis. PDE5 normally breaks down cGMP, terminating the signal. Sildenafil blocks PDE5, thereby preserving elevated cGMP levels, intensifying the natural erectile response to sexual stimulation. It has no effect in the absence of such stimulation.
Clinical Application and Dosage
The primary clinical application of Sildenafil is the treatment of erectile dysfunction of various etiologies (organic, psychogenic, or mixed). It is also used under the brand name Revatio® (at a different dose) for pulmonary arterial hypertension.
The dosage of Sildenafil is individualized. For erectile dysfunction, the recommended starting dose is 50 mg, taken orally approximately 30 minutes to 1 hour before anticipated sexual activity. Based on efficacy and tolerance, the dose may be increased to 100 mg or decreased to 25 mg. The maximum recommended dosing frequency is once per day. The 50 mg tablet strength of this Sildenafil formulation provides a standard and effective dose for most users. It can be taken with or without food, though a high-fat meal may delay its onset of action.
Treatment Protocol and Monitoring
Sildenafil is used on an as-needed, intermittent basis. Its effects typically begin within 30-60 minutes and can last for up to 4-6 hours. While monitoring specific blood markers is not required for occasional use, men with underlying cardiovascular conditions require careful evaluation before use. Blood pressure should be monitored, as Sildenafil can cause a transient decrease. It is not intended for continuous daily use for ED unless prescribed under a specific daily low-dose regimen.
Pharmacological Profile
Sildenafil is rapidly absorbed after oral administration, with an absolute bioavailability of about 40%. It reaches peak plasma concentrations within 30 to 120 minutes. It is extensively metabolized in the liver by cytochrome P450 enzymes (primarily CYP3A4) and has an elimination half-life of approximately 4 hours. Its duration of action often exceeds its plasma half-life due to its pharmacological effect at the tissue level.
Common Side Effects
Sildenafil is generally well-tolerated, but its vasodilatory effects can cause a range of side effects. The most common include:
- Headache: The most frequently reported side effect due to vasodilation.
- Flushing: A feeling of warmth and redness in the face, neck, or chest.
- Dyspepsia (Indigestion): Related to relaxation of the lower esophageal sphincter.
- Nasal Congestion: Due to vasodilation in the nasal passages.
- Dizziness: Can occur due to a transient drop in blood pressure.
- Visual Disturbances: A mild, transient blue-tinge to vision (cyanopsia) or increased light sensitivity, caused by mild inhibition of PDE6 in the retina.
- Myalgia and Back Pain: Reported in a subset of users.
Sildenafil is contraindicated in patients using any form of organic nitrates (e.g., nitroglycerin) due to the risk of a severe, potentially fatal drop in blood pressure. It is also contraindicated in men with severe cardiovascular disease, recent stroke or heart attack, or certain eye conditions like retinitis pigmentosa.
You can buy Sildenafil made by Apoxar in bulk in Canada via our website. Navigate to the “Purchase” tab and fill the contact form with details of your wholesale order. Please note: we do not sell single packs or ship directly to consumers, Apoxar is a wholesale fitness medication manufacturer and we work exclusively with our approved distributors.