How does Viagra work?
Viagra · sildenafil · by Pfizer
Reviewed by the glpzoom Editorial Team against primary clinical sources — FDA labeling, peer-reviewed trials, and specialty-society guidelines.
Content current as of June 2026; updated when guidance or availability changes.
Sildenafil blocks the PDE5 enzyme, which breaks down cGMP in penile tissue. With cGMP preserved, blood vessels stay relaxed and erection is maintained when sexually stimulated. Does not cause erection without arousal.
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Frequently asked
How does Viagra work in the body?+
Sildenafil blocks the PDE5 enzyme, which breaks down cGMP in penile tissue. With cGMP preserved, blood vessels stay relaxed and erection is maintained when sexually stimulated. Does not cause erection without arousal.
How long until Viagra starts working?+
Most patients notice appetite changes within 1-2 weeks. Meaningful weight or clinical change typically follows the full titration period (3-5 months).