
Lab TestsViagra ® is a drug designed to help men who suffer from erectile dysfunction, or impotency, to achieve an erection. Men affected by erectile dysfunction are unable to achieve an erection while sexually aroused or are unable to maintain an erection during sexual intercourse or activity. Men can purchase Viagra ® which will allow them to achieve an erection that will last throughout sexual activity, enabling them to pursue an active, healthy sex life.

A man gets an erection when he is sexually excited or stimulated due to a complex set of chemical reactions that occur in his brain and blood which result in the arteries and blood vessels of the penis dilating. This dilation increases the blood flow to the corpa cavernosa, which are the two muscular structures that run along the length of the penis' shaft. The increased blood flow engorges and stiffens the tissue, resulting in an erection.
Viagra ®'s key active component is the chemical sildenafil citrate, which is classified as a PDE5 inhibitor. The sildenafil citrate acts on the PDE5 and makes it inert, which allows the blood vessels to dilate and increase blood flow to the penis, resulting in an erection. Viagra ® is taken at least thirty minutes prior to intended intercourse, giving the drug time to absorb and become effectual. The resulting erection can last anywhere up to four hours though it usually last for around two or until after ejaculation. The drug will only take effect if the man is sexually aroused as the PDE5 required are only present at this time.
Viagra ® has been available for many years and has enabled millions of men to achieve lasting erections. Those affected by erectile dysfunction have been able to purchase Viagra ® through a doctor since its release. However it is now possible to purchase Viagra ® over the counter at a pharmacy without a doctor's prescription. It is also possible to purchase Viagra ® over the internet through a number of accredited online pharmacies and websites. Erectile dysfunction can be a distressing condition but the effectiveness of Viagra ® means that it is highly treatable.