This boosts blood flow and helps you get an erection from sexual activity. Sildenafil Viagra. Tadalafil Cialis. Some examples of nitrates are nitroglycerin Nitro-Dur, Nitrostat, others , isosorbide mononitrate Monoket and isosorbide dinitrate Bidil. Oral ED medicines might not work or might be dangerous if you also take any of the following: Nitrate medicines. Its effects often last for 4 to 5 hours. The best online pharmacies are accredited by the National Association of Boards of Pharmacy and are licensed in every state in which they trade.Sildenafil (Viagra). Tadalafil (Cialis). Vardenafil. These medicines are called PDE5 inhibitors. They enhance the effects of a chemical the body makes that relaxes muscles in the penis, called nitric oxide. This boosts blood flow and helps you get an erection from sexual activity. How oral medicines differ. Key takeaways: Muse, Caverject, and Trimix can be good substitutes for Viagra (sildenafil). But they require insertion or injection into the penis. There’s some evidence that L-arginine might help with ED as an oral supplement. But it may not be safe for everyone. There’s not much evidence that trazodone, ginseng, or yohimbine help with .  · There’s a Free, Low-Risk Alternative to Viagra, Study Shows. Regular exercise sessions can be as effective as popping Viagra pills when it comes to dealing with erectile dysfunction (ED). According to new research, just three 30 minute sessions per week could be enough to see a difference. Researchers from the Baylor College of Missing: without.