Take sildenafil exactly as directed. Sildenafil Viagra. New Zealand Sildenafil was reclassified in New Zealand in so it could be bought over the counter from a pharmacist. Generic versions of sildenafil, vardenafil and tadalafil are available. These are commonly prescribed for an enlarged prostate or male pattern baldness. If you experience chest pain, dizziness, or nausea during sexual activity, call your doctor immediately and avoid sexual activity until your doctor tells you otherwise.Sildenafil (Liqrev, Revatio) is used to improve the ability to exercise in adults (Liqrev, Revatio) and children 1 year of age and older (Revatio) with pulmonary arterial . Cost Overdose Ask your doctor Q&A Drug Images What is Viagra? If you have erectile dysfunction (ED), your doctor may recommend that you take Viagra. It’s a prescription . Sildenafil (Viagra). Tadalafil (Cialis). Vardenafil. These medicines are called PDE5 inhibitors. They enhance the effects of a chemical the body makes that relaxes muscles .