Viagra works by increasing blood flow to the penis to help a man get and maintain an erection during sexual arousal. It does this by inhibiting an enzyme called phosphodiesterase type 5 (PDE-5), which normally breaks down a chemical called cGMP responsible for relaxing the muscles in the penis and allowing blood to flow in. By blocking PDE-5, Viagra allows more cGMP to accumulate, leading to relaxed blood vessels, increased blood flow, and thus an erection when sexually stimulated. Viagra is effective only with sexual arousal and typically starts working within 30 to 60 minutes, lasting about 4 hours.
How Viagra Works Mechanistically
- Sexual arousal triggers the release of nitric oxide in the penis, which increases cGMP levels.
- cGMP relaxes smooth muscle cells and dilates blood vessels, allowing blood to fill the erectile tissue.
- PDE-5 breaks down cGMP to end the erection.
- Viagra blocks PDE-5, extending muscle relaxation and blood flow, making it easier to achieve and maintain an erection.
Timing and Effects
- Effects can begin as soon as 30 minutes after taking Viagra and usually peak around 1 hour.
- The erection hardness and duration improve, generally lasting around 4 hours.
- Viagra does not cause an erection without sexual stimulation and does not increase sexual desire directly.
In summary, Viagra assists erectile function by enhancing blood flow through chemical pathways that relax muscles in the penis during sexual excitement.
