Viagra generally refers to sildenafil, and it is important to be aware of the contraindications and adverse reactions when taking sildenafil for the first time. Sildenafil is indicated for the treatment of erectile dysfunction, and it is important to be aware of contraindications and adverse reactions when taking sildenafil for the first time. Contraindications are: contraindicated for those who are allergic to the product; contraindicated for patients taking any dosage form of nitrates, either regularly or intermittently. Use with caution in patients who have had a myocardial infarction, hypotension, hypertension, shock, heart failure, or multiple myeloma in the last 6 months Sildenafil is not indicated in women. Common adverse reactions include headache, flushing, dyspepsia, nasal congestion and visual abnormalities; long-term use of large quantities may also produce drug dependence. It is recommended to follow the doctor’s instructions to avoid increasing the dosage privately, and if serious adverse reactions occur after the use of the drug, it is necessary to consult a doctor in time to avoid serious consequences.