When taken at the correct time and paired with sexual stimulation, the erection lasts long enough for successful intercourse. Some examples of nitrates are nitroglycerin Nitro-Dur, Nitrostat, others , isosorbide mononitrate Monoket and isosorbide dinitrate Bidil. Erectile dysfunction medications require a prescription from a licensed provider. A phone or video consultation is sometimes required for legal purposes. More serious side effects may include a drop in blood pressure or an erection that lasts longer than four hours.Can you buy legitimate and legal Viagra online? Counterfeit Viagra is known to contain amphetamines, toxic chemicals, the wrong dose of active ingredients, and even blue . Medical Consultation Required: Yes. Medications Prescribed: Viagra, Cialis, sildenafil, tadalafil. Generic offered: Yes. Why We Chose It. Sildenafil. Generic name: sildenafil (oral) [ sil-DEN-a-fil ] Brand names: Revatio, Viagra. Drug classes: Agents for pulmonary hypertension, Impotence agents. Medically reviewed .