This information is reviewed by a licensed practitioner who will assess your eligibility for the medication. This increased blood flow can cause an erection. Levitra vardenafil : This medication is taken one hour before sex and can last up to 24 hours. All PDE5 inhibitors, including Viagra and Cialis, require a valid prescription regardless of the pharmacy or provider. This can happen if you are sick with fever, diarrhea, or vomiting; sweat a lot; or do not drink enough liquids. The information provided is for educational purposes only and is not intended to replace discussions with a healthcare provider.Sildenafil (Viagra) is used to treat erectile dysfunction (impotence; inability to get or keep an erection) in men. 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 hypertension (PAH; high blood pressure in the vessels carrying blood to the . Examples of Viagra’s more commonly reported side effects include: headache. flushing (temporary warmth, redness, or deepening of skin color) stuffy nose. indigestion (upset stomach) mild vision. DRUG_DESCRPTION Compare DRUG_NAME prices and find coupons that could save you up to 80% instantly at pharmacies near you such as CVS, Walgreens, Walmart, and .