Viagra, or sildenafil, primarily targets an enzyme called phosphodiesterase-5 (PDE5). This enzyme normally breaks down a molecule called cyclic guanosine monophosphate (cGMP).
CGMP and Blood Flow
CGMP plays a crucial role in the relaxation of smooth muscle tissue in the penis. When sexually stimulated, nitric oxide (NO) is released, leading to increased cGMP levels. This elevated cGMP causes the smooth muscles in the blood vessels of the penis to relax, allowing increased blood flow and creating an erection.
PDE5’s job is to degrade cGMP, thus limiting the duration of the erection. Viagra inhibits PDE5. By preventing the breakdown of cGMP, Viagra allows for sustained higher levels of cGMP, promoting and maintaining penile blood flow.
Viagra’s Mechanism of Action: A Step-by-Step Guide
Sexual stimulation triggers the release of nitric oxide (NO). NO activates an enzyme called guanylate cyclase. Guanylate cyclase increases the production of cGMP. Increased cGMP levels cause relaxation of smooth muscles in the penile arteries. Relaxed arteries allow increased blood flow into the penis. Viagra inhibits PDE5, preventing the breakdown of cGMP. Sustained high levels of cGMP maintain relaxation of penile arteries. This results in a sustained erection.
Specific Target and Resulting Effects
The specific target is PDE5, an enzyme found throughout the body, but its concentration is particularly high in the penis. Therefore, Viagra’s effects are most noticeable in erectile function. Side effects can occur because PDE5 is present in other areas, albeit at lower concentrations. These can include headaches, facial flushing, and nasal congestion.
In summary, Viagra’s mechanism enhances the natural physiological processes involved in achieving an erection by increasing and prolonging the effects of cGMP, a key molecule for blood vessel dilation in the penis.
