By controlling the enzyme, sildenafil helps to maintain an erection after the penis is stroked. Here are some key factors to consider when deciding: Pricing: Know how much your monthly supply will cost with shipping and tax. You’ll also need to fill out a medical questionnaire with answers about your medical history, current medications, and lifestyle habits. Recent heart or blood vessel problems. Privacy: Confirm that your personal data and payment details are confidential. Side effects Side effects of oral ED medicines are often mild.In addition to Viagra, REX MD also offers brand-name Cialis and generic Cialis (tadalafil). Both Viagra and sildenafil are available in mg, mg, and mg doses. Typical dosing for Sildenafil (Viagra) The typical dose is to take 50 mg of sildenafil (Viagra) by mouth, about 1 hour before sex, as needed. The maximum recommended dose is mg. Don’t take sildenafil (Viagra) more than once daily (at any dose). Written by Brian Leonard, PharmD, BCACP, BCGP. Common Brand(S): Viagra Generic Name(S): sildenafil. Uses; Side Effects; Precautions; Interactions; Overdose; nor should it be construed to indicate that use of a particular drug is safe.