Description

Overview

Sildenafil, commonly known by its brand name Viagra, is a phosphodiesterase-5 (PDE-5) inhibitor used primarily for the treatment of erectile dysfunction (ED) and pulmonary arterial hypertension (PAH). It was the first FDA-approved oral ED medication and remains one of the most widely used treatments for men experiencing difficulty achieving or maintaining an erection.

Unlike Tadalafil (Cialis), which has a longer half-life, Sildenafil works for about 4 to 6 hours, making it ideal for on-demand use.

Mechanism of Action

Sildenafil works by blocking the PDE-5 enzyme, which is responsible for breaking down cyclic guanosine monophosphate (cGMP) in the penis. By inhibiting PDE-5:

• cGMP levels increase, causing smooth muscle relaxation and vasodilation in the penile blood vessels.
• This allows greater blood flow, leading to a stronger and more sustained erection when sexually aroused.
• Sildenafil does not cause an erection on its own; sexual stimulation is required for it to be effective.

Benefits & Indications

1. Erectile Dysfunction (ED)

• Helps men achieve and maintain firm erections
• Works within 30–60 minutes after ingestion
• Effective in mild, moderate, and severe ED cases
• Available in 25 mg, 50 mg, and 100 mg doses

2. Pulmonary Arterial Hypertension (PAH)

• Sold under the brand Revatio for lowering blood pressure in pulmonary arteries
• Improves exercise capacity in PAH patients

3. Off-label Uses

• Studied for altitude sickness prevention
• Potentially helpful in Raynaud’s phenomenon (cold-induced blood vessel spasms)

Possible Side Effects

• Headache, flushing, and dizziness
• Nasal congestion and indigestion
• Blurred vision or a blue-tinted vision (cyanopsia)
• Hypotension (low blood pressure), especially when taken with nitrates
• Priapism (prolonged erection lasting over 4 hours, requiring emergency treatment)

Drug Interactions

• Nitrates (e.g., Nitroglycerin, Isosorbide Mononitrate): Can cause severe blood pressure drops
• Alpha-blockers (Tamsulosin, Doxazosin): Can lead to fainting and dizziness
• CYP3A4 inhibitors (Ritonavir, Ketoconazole): Can increase Sildenafil levels in the blood
• Alcohol: May worsen dizziness and hypotension