Keep from freezing. It might work longer if you have mild to moderate erectile dysfunction. Adults 65 years of age and older—25 mg as a single dose no more than once a day, 1 hour before sexual intercourse. This medication is taken with or without food an hour before sex. Side effects Side effects of oral ED medicines are often mild.Learn about uses, how it works, and more for Viagra (sildenafil). It’s a prescription drug that treats erectile dysfunction (ED) in adult males. Brand: Viagra. Form: oral tablet; Strengths: 25 mg, 50 mg, mg; Adult dosage (ages 18–64 years) Typical dosage: 50 mg, taken as needed about 1 hour before sexual activity. It can be taken The original little blue pill prescribed by doctors for over 20 years Clinically proven to treat men with erectile dysfunction (ED) Ongoing commitment to product quality and safety monitoring Learn More IF YOU CHOOSE BRAND-NAME VIAGRA, MAKE SURE YOU GET THE BRAND NAME.