Tadalafil belongs to which class of drugs?

• A. Beta Blockers
• B. PDE5 Inhibitors
• C. ARBs
• D. ACE Inhibitors

Answer: (B)

This question tests drug class based on how the drug works. Tadalafil is a PDE5 inhibitor. In erection, sexual stimulation releases nitric oxide, which increases cyclic GMP (cGMP) in the smooth muscle of the corpus cavernosum, causing relaxation and filling with blood. PDE5 normally breaks down cGMP, ending the erection. By inhibiting PDE5, tadalafil keeps cGMP levels higher, promoting and sustaining an erection in response to arousal. This mechanism is specific to the penile tissue and explains its use for erectile dysfunction (and related conditions). The other listed classes do not act via this cGMP pathway: beta blockers affect adrenergic receptors, ARBs block angiotensin II receptors, and ACE inhibitors block the enzyme that makes angiotensin II.