Sildenafil is an on-demand pill that lasts for up to five hours. But if someone takes Viagra with cocaine, they’re at risk for priapism, heart attack or stroke. In psychogenic erectile dysfunction, psychological issues prevent maintaining or getting an erection — nothing physical. The effectiveness of Sildenafil has been reviewed in clinical studies. The bottom line: It’s safe to take as prescribed. · Before taking this medicine. You should not use sildenafil if you are allergic to it, or: if you take other medicines to treat pulmonary arterial hypertension, such as . Generic name: sildenafil (oral) [ sil-DEN-a-fil ] Brand names: Revatio, Viagra Drug class: Impotence agents Medically reviewed by Sophia Entringer, PharmD. .  · 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 .