Viagra, also known as sildenafil citrate tablets, is mainly used to improve erectile dysfunction in men, and its effects usually last for 2-4 hours. It is generally recommended to be taken 1 hour before sexual intercourse, as the peak concentration time after oral administration of this drug is usually 30-120 minutes, with an average time to peak of about 1 hour for most patients. Studies have shown that the effective duration of action of this drug can last up to 4 hours, but for most patients, there is usually a better therapeutic effect in the first 2 hours, and the effect in the last 2 hours is actually weaker. In addition, when taking the drug, it should be noted that the drug can only have a therapeutic effect under conditions of sexual stimulation, so it is necessary to have sexual stimulation in order for the drug to have a better therapeutic effect. It is recommended that patients must take it on an empty stomach or 2 hours after a meal, if eating high-fat, greasy food will significantly delay the onset of action. At the same time before and after taking the drug should not drink alcohol, and should not take a hot bath, to maintain a good state of mind.