Viagra is an erectile dysfunction medication manufactured by Pfizer. It contains Sildenafil Citrate. Viagra is available in different strengths however the most popular strength of Viagra is 100mg. Men buy Viagra across the globe, however the proper way to use a Viagra tablets is to consume this medication on doctor’s prescription. The duration for which Viagra tablet effects can be observed is 4-5 hours. Ishoppharmacy.com provides complete information on Viagra and its alternatives.