Viagra / Zeagra (Sildenafil Citrate)

Sildenafil citrate is a medication most commonly known under the brand name Viagra (and also used in Revatio). It belongs to a drug class called PDE5 inhibitors.

• Erectile dysfunction (ED): Helps increase blood flow to the penis during sexual stimulation.
• Pulmonary arterial hypertension (PAH): Marketed as Revatio for lowering blood pressure in the lungs and improving exercise ability.
• Raynaud’s phenomenon (off-label): Sometimes prescribed to reduce episodes.

• Sildenafil blocks the enzyme phosphodiesterase type 5 (PDE5).
• This increases cyclic GMP (cGMP) levels, which helps relax smooth muscle and dilate blood vessels.
• In ED, this means better blood flow to the penis.
• In PAH, it lowers pulmonary blood pressure.
• Dosage (typical ranges):
• ED: 25 mg, 50 mg, or 100 mg as needed, about 30–60 minutes before sexual activity (not more than once daily).
• PAH (Revatio): 20 mg three times daily.

• Headache, flushing, nasal congestion
• Indigestion
• Vision changes (blue/blurred vision)
• Dizziness, low blood pressure
• Rare but serious: priapism (prolonged erection), sudden hearing or vision loss, cardiovascular events.

• Do not take with nitrates (e.g., nitroglycerin) → can cause dangerous drops in blood pressure.
• Caution with heart disease, recent stroke/MI, severe liver or kidney impairment.
• Interaction with certain drugs (alpha-blockers, CYP3A4 inhibitors).