Sildenafil citrate is the active ingredient in Viagra®. It belongs to the PDE5 inhibitor class. All generic brands below contain the same pharmaceutical-grade sildenafil. Reviewed by Dr. Priya Sharma, MD.
Sildenafil inhibits the enzyme phosphodiesterase type 5 (PDE5), which is responsible for the breakdown of cGMP in smooth muscle cells. By inhibiting PDE5, sildenafil allows cGMP to accumulate, causing smooth muscle relaxation and increased blood flow to the corpus cavernosum of the penis during sexual stimulation.
It does not cause erections without sexual arousal — stimulation is still required. Effect begins 30–60 minutes after ingestion and lasts 4–6 hours.
Sildenafil inhibits the enzyme phosphodiesterase type 5 (PDE5), which is responsible for the breakdown of cGMP in smooth muscle cells. By inhibiting PDE5, sildenafil allows cGMP to accumulate, causing smooth muscle relaxation and increased blood flow to the corpus cavernosum of the penis during sexual stimulation.
It does not cause erections without sexual arousal — stimulation is still required. Effect begins 30–60 minutes after ingestion and lasts 4–6 hours.
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