If you are having trouble maintaining or achieving an erection during sexual intercourse, you may be suffering from a condition called erectile dysfunction. This is a very common medical condition that afflicts men of all ages and backgrounds around the world. Fortunately, a pharmaceutical company called Pfizer created a small blue pill called Viagra that was first made available to the public in 1998. Viagra works by stopping the breakdown of an enzyme called CGMP specific phosphodiesterase type 5. This enzyme regulates blood flow to the penis, which helps men to achieve an erection. The pill is available in 25mg, 50mg and 100mg doses and is taken orally. The effects normally start within 30 minutes of taking the pill and last approximately 3 to 4 hours afterwards. It’s also important to note that Viagra only works in conjunction with sexual stimulation. So, if you having trouble with erections, be sure to talk to your doctor about Viagra or conduct a search online for the drug.