Medicines that block an enzyme called CYP3A4. Stendra avanafil : This is an as-needed medication taken 30 minutes before sex and can last up to six hours. These PDE5 inhibitors may cause headache, flushing, drop in blood pressure, or other adverse effects. People taking nitrates like nitroglycerin Nitrostat or isosorbide mononitrate Imdur should not take PDE5 inhibitors, as doing so could result in a dangerous drop in blood pressure. Vardenafil usually works for 4 to 5 hours.It may also be used to treat the enlargement of the prostate gland. This drug is slightly more popular than comparable drugs. It is available in both brand and generic versions. Cialis . Cialis is only available by prescription in the United States. Viagra: Additionally, a study from Trusted Source. found that combining L-arginine and . Published on October 18, warning This article is no longer being updated and some information may not be current. Visit the GoodRx Healthhomepage for our latest articles. .