Viagra is the trade name, generic name of sildenafil citrate tablets, the first time to take to pay attention to the indications, dosing time, contraindications and so on. 1. Indications: This product has the effect of dilating penile blood vessels, promote penile erection, used in the treatment of erectile dysfunction. 2. Dosing time: This product is taken on demand roughly one hour before sexual activity, up to one time per day. 3. Contraindications: This product may enhance the antihypertensive effect of nitrate. Therefore, this product is contraindicated for people who take any dosage of nitrate regularly or intermittently. Combining this product with guanylate cyclase agonists such as leucovorin is prohibited and may cause symptomatic hypotension. It is contraindicated in persons with known hypersensitivity to the ingredients in this product. Adverse reactions to sildenafil citrate tablets can be seen as headache, dizziness, blurred vision, flushing, nasal congestion, nausea, and indigestion. Patients taking the drug for the first time should consult a doctor and use it appropriately under his or her guidance.