If you are a Mayo Clinic patient, this could include protected health information. However, if you take sildenafil with a high-fat meal, it will take longer for the medication to start to work. Perhaps most striking is that the generic will not have the signature blue color. As with sildenafil, a high-fat meal or alcohol keep the body from absorbing it as quickly. Your doctor or other health care professional can recommend one for you based on these factors, other health conditions you have and any other medicines you take. These include itraconazole Sporanox, Tolsura , ketoconazole Extina, Ketozole, others and ritonavir Norvir. The best time to take sildenafil is about 1 hour before sexual activity, but you can take the medication any time from 4 hours to 30 minutes before sexual activity.Generic versions of sildenafil, vardenafil and tadalafil are available. When oral medications might not be safe Check with your health care team before you take any medicine for erectile dysfunction. Costs. Viagra is a brand-name drug, while sildenafil is a generic form of Viagra. Brand-name medications usually cost more than generics. The actual price you’ll pay for either drug depends. According to price-comparison site test1.ru, generic Revatio will cost you as little as $ per pill, depending on where you fill your prescription. That’s compared with more than $50 per.