Viagra, generally referred to as sildenafil citrate tablets, is used orally, and for most patients, the recommended dose is 50mg, taken anytime between 0.5 and 4 hours before sexual activity. It should be taken up to once a day. And it is important to note that taking the drug requires sexual stimulation for it to work; when taken without sexual stimulation, sildenafil citrate tablets will not work. Sildenafil citrate tablets are indicated for the treatment of erectile dysfunction. Its adverse effects include blurred vision, nasal congestion, runny nose, back pain, muscle pain, nausea, dizziness, and rash. Nitrate drugs such as isosorbide nitrate tablets are contraindicated after taking sildenafil citrate tablets, otherwise it may lead to low blood pressure causing a series of serious symptoms. Sildenafil citrate tablets must be used under the guidance of a doctor or pharmacist, taken in accordance with medical advice, and must pay attention to contraindications.