The mechanism of action of sildenafil used in erectile dysfunction is:
A
Angiotensin-converting enzyme inhibitor
B
Phosphodiesterase type 5 inhibitor
C
HMG-CoA reductase inhibitor
D
Cholinesterase inhibitor
Correct Option:
B
Explanation
Sildenafil selectively inhibits phosphodiesterase type 5 (PDE5). Nitric oxide normally increases cGMP in corpus cavernosum smooth muscle. PDE5 breaks that cGMP down. By inhibiting PDE5, sildenafil prolongs cGMP-mediated smooth-muscle relaxation and facilitates penile blood flow during sexual stimulation. It does not act as an ACE inhibitor, HMG-CoA reductase inhibitor or cholinesterase inhibitor.
