Viagra Vigo is the trade name and generic name for sildenafil citrate tablets, and the dosage instructions are for a recommended dose of 50 mg for the average patient. Currently sildenafil citrate tablets, taken up to once daily, are recommended to be taken for the first time by most patients at a dose of 50 milligrams, to be taken on an as-needed basis approximately one hour prior to sexual activity. Subsequent doses may be increased to a maximum of 100 mg or decreased to 25 mg taken prior to each sexual encounter based on efficacy and tolerability. Note that the recommended dose of sildenafil does not work in the absence of sexual stimulation. Sildenafil is contraindicated in patients taking any dosage form of nitrate; in patients with known hypersensitivity to any of the components of the product; and in patients whose cardiovascular status precludes sexual activity. Adverse reactions such as present headache, dizziness, flushing, nasal congestion, dyspepsia, and visual abnormalities may occur during administration. The drug is a prescription drug, please use it under the guidance of a doctor, do not blindly take it by yourself, so as not to cause side effects.