Smith1; Mary Babos2. Contraindications Nitrates increase cGMP formation, while sildenafil inhibits cGMP degradation causing the combination to produce severe life-threatening hypotension synergistically; coadministration of sildenafil with nitrates is contraindicated. Most patients receive a prescription for 50 mg of oral sildenafil, taken as needed approximately 1 hour before sexual activity. Viagra is designed to improve your physical performance during sex — that is, your ability to get and maintain an erection. Sudden vision loss in one or both eyes can be a sign of a serious eye problem called non-arteritic anterior ischemic optic neuropathy NAION. We rely on peer-reviewed studies, academic research institutions, and medical associations. Viagra can also have an indirect psychological effect by making you feel more confident in bed, which may improve your sexual experience overall.Generic Viagra (sildenafil) is available as a , , , and milligram (mg) pill and in liquid form. It’s meant to be taken as needed — about an hour before sex — but shouldn’t be. What Is Viagra? Viagra® has one of the biggest glow-up stories in the world of ally designed as a blood pressure medication for people trying to avoid chest pain and stiff left arms, it quickly became clear that the little blue pill’s most curious side effect wasn’t causing low blood pressure, but making something else (yes, a penis) .  · Maximum dose: 20 mg orally three times a day. Injection: Initial dose: or 10 mg IV bolus three times a day. Comments: No greater efficacy was achieved with oral doses higher than the maximum recommended dose. A 10 mg injection dose is predicted to provide pharmacological effect equivalent to the 20 mg oral dose.