Mutagenesis Sildenafil was negative in in vitro bacterial and Chinese hamster ovary cell assays to detect mutagenicity, and in vitro human lymphocytes and in vivo mouse micronucleus assays to detect clastogenicity. Some medications should not be taken with sildenafil. Follow the manufacturer’s directions to use and clean the oral syringe. One-third to one-half of the subjects in these studies reported successful intercourse at least once during a 4-week, treatment-free run-in period. This increased blood flow can cause an erection. These effects on the metabolite are not expected to be of clinical consequence.Get sildenafil for as low as $, which is 95% off the average retail price of $ for the most common version, by using a GoodRx coupon. Prices Medicare Drug Info Side Effects Images Sildenafil (Viagra, Revatio) is a moderately priced drug used to treat erection problems in men. 1 day ago · Cost: If the price for branded Viagra is outside of your budget, Viagra is available in mg, mg, and mg doses and can be purchased in day and day supplies. Shipping is free, and. The smallest available dose, 25 milligrams (mg), won’t last as long as the largest available dose, mg. But taking a higher dose isn’t always recommended, as it may not be safe for you. Age.