Do not take it more than 3 times a day. This medicine also works best when you take it an hour before sex on an empty stomach. The FDA has approved a daily pill called flibanserin Addyi — originally developed as an antidepressant — as a treatment for low sexual desire in premenopausal women. Tadalafil Cialis. As a rough guide to the differences between treatments, listed below are the basic costs of medicines before a dispensing charge is added. If you experience chest pain, dizziness, or nausea during sex, seek immediate medical help. · Take sildenafil exactly as it was prescribed for you. Follow all directions on your prescription label and read all medication guides or instruction sheets. Revatio is usually taken three times each day, about 4 to 6 hours apart. Viagra is usually taken only when needed, 30 minutes to 1 hour before sexual activity. If VIAGRA is prescribed to patients taking ritonavir, caution should be used. Data from subjects exposed to high systemic levels of sildenafil are limited. Decreased blood pressure, syncope, and prolonged erection were reported in some healthy volunteers exposed to high doses of sildenafil ( mg).  · Unless you are prescribed generic sildenafil, the strict criteria for NHS treatment means your GP can only provide ED treatment as a private prescription. However they can’t charge you for doing so.