Yes, ED pills can cause side effects. An inherited eye disease that affects the retina. Concomitant administration of strong CYP3A4 inducers, such as rifampin, is expected to cause greater decreases in plasma levels of sildenafil. Here are some steps that might help: If you smoke, quit. If you have trouble quitting, get help. They’re often the first line of treatment for trouble getting or keeping an erection, called erectile dysfunction ED.Viagra is absorbed quickly into your body. It can start working within 30 minutes, but it may take a couple hours for some people. However, one study on Viagra found that about 70% of men achieved erections in 30 minutes, and more than 80% of men achieved erections within 45 minutes. For most men, the effects of Viagra will start within .  · 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. Don’t take sildenafil (Viagra) more than once a day because doing so can put you at higher risk for serious side effects, such as vision loss or low blood pressure. It’s available as a .