This applies, for example, when you want to take Tadalafil brand name Cialis instead of Viagra. The body takes longer to absorb it after a high-fat meal or alcohol. Get an online prescription and buy from a reputable online service. Vardenafil usually works for 4 to 5 hours. You can also buy Viagra, generic unbranded Sildenafil , and other licensed ED treatments online, from approved sites, without needing to visit your GP. Its effects might last longer if you have mild to moderate ED. Avanafil Stendra.Currently, there are no over the counter alternatives to Viagra available. Viagra (sildenafil) is a prescription medication, meaning it’s not available over the counter from your. Generic Viagra (sildenafil) is an alternative to the branded Viagra drug that can be used for treating erectile dysfunction (ED). It’s now sold by many manufacturers, including online. The smallest available dose, 25 milligrams (mg), won’t last as long as the largest available dose, mg. Should Viagra Be an Over-the-Counter Drug? Viagra will soon be .