They’re often the first line of treatment for trouble getting or keeping an erection, called erectile dysfunction ED. Online pharmacies can be broadly categorized as: Mail-order pharmacies are operated by pharmacy benefits managers PBMs on behalf of health insurers or providers. Cialis tadalafil : This ED medication works with the same principle as Viagra, but lasts up to 36 hours. Shipping: Discreet, fast shipping is a must. More serious side effects may include a drop in blood pressure or an erection that lasts longer than four 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 . sildenafil citrate or viagra Savings, Coupons and Information. | SILDENAFIL (sil DEN a fil) treats erectile dysfunction (ED). It works by increasing blood flow to the penis, which . Sildenafil generic Revatio and Viagra Used for Pulmonary Hypertension and Erectile Dysfunction MORE expand_more Check your prescription Prescription 20mg sildenafil .