The generic versions are just as effective and much less expensive. It lasts 4 to 5 hours, or longer if you have mild to moderate ED. If approved, the provider will issue a prescription. Kidney disease that needs to be treated with dialysis. Payment options: Consider how you’d like to pay.Sildenafil (Viagra). Tadalafil (Cialis). Vardenafil. These medicines are called PDE5 inhibitors. They enhance the effects of a chemical the body makes that relaxes . Viagra (, 50, 25 and 20mg) takes about 30min to have full effect but cannot be taken with food, as it can diminish the result. The 20mg dose can also be compounded at . There is generic Viagra now. They have 20mg and mg tablets. It’s usually $/bottle depending on your pharmacy. Related Reddit Ask Online community Social media .