Viagra, also known as sildenafil citrate tablets, is a medication that is primarily used to treat erectile dysfunction in men, and is usually best taken about an hour before sexual activity. Studies have shown the drug to be effective when taken anytime between 0.5 and 4 hours before sexual activity. However, to make the medication work better, it is generally recommended to take it 1 hour before sexual activity. There is a better therapeutic effect, which is related to the metabolism of the drug, because the drug after oral intake usually in the range of 30-120 minutes can reach the peak blood concentration, the average time is 60 minutes, so it is generally recommended that patients take 1 hour before sexual activity, the effect is better. But when taking the drug, you need to pay attention, if the patient has cardiovascular and cerebrovascular diseases, must be taken under the guidance of the doctor. In short, it is generally recommended to take 1 hour before sexual activity, and there should be sexual stimulation, if there is no condition of sexual stimulation, this drug is not obvious effect. You should not drink alcohol or take a shower before or after taking sildenafil. It is also not suitable if you have low blood pressure or refractory hypertension, have had a myocardial infarction or stroke within six months. Although it is more widely used, try to take it under the guidance of a doctor and read the instructions in detail before taking it.