If you prefer, you may contact the U. If you are taking sildenafil for erectile dysfunction, your doctor will probably start you on an average dose of sildenafil and increase or decrease your dose depending on your response to the medication. Phosphodiesterase type 5 PDE5 inhibitors. Always talk to your doctor about the risks and benefits of any treatment. Tell your doctor if sildenafil is not working well or if you are experiencing side effects. Sildenafil treats PAH by relaxing the blood vessels in the lungs to allow blood to flow easily.FUTRELL PHARMACY OF LITTLETON. $ E S Main St. Littleton, NC mi. Closed. () Get Coupon. Add to Pricing Basket. Sildenafil is a generic drug, which is an exact copy of the active drug in a brand-name medication. The generic is considered to be as safe and effective as the original drug. . 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.