Amazon Pharmacy: Teva Pharma SILDENAFIL 25 MG TABLET Viagra takes around 30 minutes to become effective and lasts about 4 hours. Cialis lasts much longer - up to 36 hours in some cases. Stendra can start doing its thing in as little as 15 minutes Viagra 50mg is the standard starting dose for most people, and is what we recommend if you ve never tried Viagra before. 50mg is the most popular dosage of...