Sildenafil (Viagra brand) only works following sexual stimulation. It works within 30 to 60 minutes, but may be taken up to four hours before sexual activity. Sildenafil (Revatio .Avanafil Stendra. A newer form of the medicine that dissolves on the tongue might work faster than the pill that you swallow. The Korean Court system made a ruling against Pfizer in June , allowing for the unhindered domestic production of generic prescription sildenafil. Condensation with 1-methylpiperazine. Seven of these companies are based in India. Oral medicine for ED also might not be safe or work well if you have: Very low blood pressure, called hypotension, or uncontrolled high blood pressure, called hypertension. Generic versions of sildenafil, vardenafil and tadalafil are available.The primary indication of sildenafil is treatment of erectile dysfunction (inability to sustain a satisfactory erection to complete sexual intercourse). Its use is now one of the standard . 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 drug that’s used in adult males* with . “Generic Revatio is considerably less expensive, and it is the same drug as Viagra with the same safety and effectiveness,” says Bradley Anawalt, M.D., an endocrinologist and .They enhance the effects of a chemical the body makes that relaxes muscles in the penis, called nitric oxide. As with sildenafil, a high-fat meal or alcohol keep the body from absorbing it as quickly. Generic versions of this low-dose form of sildenafil have been available in the U. You can take this medicine with or without food 30 minutes before sex, depending on the dose. Often, these are prescribed for chest pain called angina. When oral medications might not be safe Check with your health care team before you take any medicine for erectile dysfunction.