As in the other titration studies, patients were started on 50 mg and allowed to adjust the dose up to mg or down to 25 mg of VIAGRA; all patients, however, were receiving 50 mg or mg at the end of the study. Your doctor may adjust your dose as needed and tolerated. Sildenafil may cause side effects. The best time to take sildenafil is about 1 hour before sexual activity, but you can take the medication any time from 4 hours to 30 minutes before sexual activity. Call your doctor right away if you have blurred vision, confusion, dizziness, faintness, or lightheadedness when getting up from a lying or sitting position suddenly, sweating, or unusual tiredness or weakness.Who may not be able to take sildenafil. Sildenafil is not suitable for some people. To make sure it’s safe for you, speak to your doctor or pharmacist before taking sildenafil if you: have ever had an allergic reaction to sildenafil or any other medicine. have recently had a stroke, heart attack or a heart problem – your doctor should. Is there a safe/reliable place to buy generics? I know there is no official generic, but it looks like there are a lot of sources outside of the US that make generics. Apparently our .  · The effects may be increased because of slower removal of the medicine from the body. Leukemia (blood related cancer) or. Multiple myeloma (blood related cancer) or. Sickle-cell anemia (blood disorder)—Sildenafil should be used with caution in these patients as problems with prolonged erection of the penis may occur.