4 known interactions • 3 major • 1 moderate • 0 minor
Always disclose all medications to your healthcare providers — prescription medicines, OTC medications, vitamins, and herbal supplements. This list may not include every possible interaction. Use our Medicine Interaction Checker to screen your complete medication list.
Potentially life-threatening or causing permanent damage. Avoid combination.
May worsen condition or require dose adjustment. Monitor closely.
Usually limited clinical effect. Manage with routine monitoring.
Nitrates (nitroglycerin, isosorbide mononitrate/dinitrate, amyl nitrite 'poppers')
ABSOLUTELY CONTRAINDICATED. Both sildenafil and nitrates lower blood pressure via cGMP/nitric oxide pathways. Combination causes severe, potentially fatal hypotension. Can occur even 24–48 hours after sildenafil dose.
Management: Absolutely contraindicated. Do not use within 24 hours of sildenafil (48 hours for tadalafil). In emergency nitrate use after sildenafil, aggressive IV hemodynamic support is required.
Alpha-blockers (tamsulosin, doxazosin, terazosin)
Additive hypotension. Combination can cause significant symptomatic hypotension, especially with doxazosin.
Management: Use with caution; start sildenafil at 25mg. Separate dosing by ≥4 hours. Tamsulosin has least interaction.
Strong CYP3A4 inhibitors (ritonavir, ketoconazole, erythromycin)
CYP3A4 inhibitors markedly increase sildenafil plasma levels (ritonavir increases AUC by 11-fold).
Management: With ritonavir: max 25mg every 48 hours for ED. With ketoconazole: max 25mg/day.
Antihypertensives
Additive hypotension possible, though usually mild with monotherapy at standard doses.
Management: Monitor blood pressure; advise patients about postural hypotension.
Always ask your pharmacist about potential interactions with food, alcohol, and supplements specific to Sildenafil. Some medicines have significant interactions with grapefruit juice, high-fat meals, dairy products, or vitamin K-rich foods.