Very rarely, Viagra can lead to temporary memory loss, heart attack, seizures, chest pain, shortness of breath, irregular heartbeat, low blood pressure accompanied with dizziness, fainting and light-headedness, stroke and pulmonary hemorrhage. The effect of the tablet lasts for up to 4 hours. Kidney Disease or reduced kidney function may cause Viagra Sildenafil to build up in the body, causing side effects. The contents herein are for informational purposes only. The orders are usually shipped in working days after the processing of the order. Prolonged erection: If an erection lasts longer than 4 hours a rare occurrence , seek immediate medical assistance.Sildenafil (Viagra). Tadalafil (Cialis). Vardenafil. These medicines are called PDE5 inhibitors. They enhance the effects of a chemical the body makes that relaxes muscles . DIN (Drug Identification Number) How does this medication work? What will it do for me? Sildenafil belongs to a group of medications called phosphodiesterase type 5 inhibitors. . The medication Viagra is manufactured by Pfizer Canada Inc and it comes in 25 mg, 50 mg and mg dosage forms in a blister pack of 4 tablets. Do not drink alcohol while .