This medicine is available only with your doctor’s prescription. Shipping: Discreet, fast shipping is a must. An erection results from an increase in blood flow to the penis. Alpha-blockers are sometimes prescribed for prostate problems or high blood pressure. Contact your medical provider if you experience any side effects during treatment. Sildenafil belongs to a group of medicines called phosphodiesterase 5 PDE5 inhibitors.Drug Facts. Common Brands Viagra. Drug Class PDE-5 inhibitor. Controlled Substance Classification Not a controlled medication. Generic Status Lower-cost generic available. Availability Prescription only. How Sildenafil (Viagra) works. Sildenafil (Viagra) is a phosphodiesterase-5 (PDE-5) inhibitor. How to Get Generic Viagra – Consumer Reports. An inexpensive blood pressure medication might be an option for some men who suffer from erectile dysfunction. By Ginger Skinner. Last updated: June. A sildenafil (generic Viagra) membership starts at $20 monthly for six tablets of 30 mg. For $ each month, you’ll receive 34 sildenafil tablets of 45 mg each. Generic Viagra (sildenafil): $20 to $ per month. Generic Cialis (tadalafil): $20 to $ per month.