Viagra (sildenafil citrate) is a PDE5 medicine that has been specially designed for the treatment of male impotence. This condition affects males even if they are quiet young, and may be characterized by the loss of ability to perform sexually due to a number of factors. This drug has been intended for males only and is not supposed to be taken by women. Each dose of Viagra is supposed to be taken before you have sex, is it expected to give you up to 4 hours of efficiency. This means you will be able to attempt sexual intercourse at any moment within this period. Make sure you always discuss all the aspects with a qualified health care professional. Online pharmacies often offer this kind of services, and you can easily get a free consultation. Make sure you tell your doctor if you get irregular heartbeat, light-headedness, nausea, vision changes, sudden hearing loss, chest pain, general ill feeling, sweating, ringing in your ears, sudden vision loss, shortness of breath, or swelling in your hands, as those are considered serious side effects of Viagra. At the same time, however you may get a few mild side effects that do not need to be reported and include muscle ache, backache, headache, and stuffy nose.