You can take this medicine with or without food 30 minutes before sex, depending on the dose. Its effects might last longer if you have mild to moderate ED. These include a heart attack, stroke or a serious heart rhythm disorder in the past six months. Tadalafil Cialis. They enhance the effects of a chemical the body makes that relaxes muscles in the penis, called nitric oxide. Some people may also have ringing in their ears tinnitus or dizziness.Sildenafil generic Revatio and Viagra Used for Pulmonary Hypertension and Erectile Dysfunction MORE expand_more Check your prescription Prescription 20mg sildenafil (30 tablets) edit Choose your pharmacy moses lake, WA Safeway Walgreens Rite Aid info How to use this discount phone Need help? Show this coupon to your pharmacist. 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 ED. With ED, you. Clinically proven to treat men with erectile dysfunction (ED) Ongoing commitment to product quality and safety monitoring Learn More IF YOU CHOOSE BRAND-NAME VIAGRA, MAKE SURE YOU GET THE BRAND NAME Your prescription may have been filled with a generic version instead of brand-name VIAGRA.