He defines erectile dysfunction as the inability to get or keep an erection for satisfactory sexual performance. You should only be treated with one of these products at a time. Rarely reported side effects include: an erection that will not go away priapism. Some examples of nitrates are nitroglycerin Nitro-Dur, Nitrostat, others , isosorbide mononitrate Monoket and isosorbide dinitrate Bidil. Side effects of medications used to treat other health problems negatively impact erections.Viagra is approved for this use in males ages 18 years and older. Viagra contains the drug sildenafil. It belongs to a class of drugs called phosphodiesterase type 5 (PDE5) . Specifically, you may have a lower starting dosage than usual if you’re over age For example, a year-old might start at a dose of 50 milligrams (mg), while a year-old . Sildenafil (Viagra brand) only works following sexual stimulation. It works within 30 to 60 minutes, but may be taken up to four hours before sexual activity. Sildenafil (Revatio .