The most common side effects of sildenafil reported by Ro members include: stuffy/runny nose, flushing, headaches, heartburn, dizziness, muscle aches, and nausea.

Do not take Viagra if you take any medicines called nitrates, often prescribed for chest pain, or guanylate cyclase stimulators like Adempas (riociguat) as this can result in a sudden, dangerous drop in blood pressure. You should not use Viagra if you are not healthy enough for sex. Seek emergency treatment if an erection lasts more than 4 hours. Use caution when taking Viagra with alpha-blockers or other anti-hypertensives because it may lead to a drop in blood pressure. Stop Viagra and seek medical care if a sudden loss of vision occurs in one or both eyes, which could be a sign of non-arteritic anterior ischemic optic neuropathy (NAION). Stop Viagra and seek medical care if sudden decrease or loss of hearing occurs. The most common side effects are headache, flushing, upset stomach, abnormal vision, stuffy or runny nose, back pain, muscle pain, nausea, dizziness, and rash. For more information, see Important Safety Information.