Click here for an email preview. You can take it in a small dose daily or in a larger dose as needed. The best time to take sildenafil is about 1 hour before sexual activity, but you can take the medication any time from 4 hours to 30 minutes before sexual activity. These medicines all work well for ED. It was initially studied for use in hypertension high blood pressure and angina pectoris a symptom of ischaemic heart disease.In fact, a recent review of studies found that some counterfeit drugs contained a very high, dangerous level of sildenafil that far exceeded a typical . Sildenafil (Viagra). This medicine works best when you take it on an empty stomach an hour before sex. The body takes longer to absorb it after a high-fat meal or .  · Descriptions Sildenafil is used to treat men who have erectile dysfunction (also called sexual impotence). Sildenafil belongs to a group of medicines called .