PDE5 inhibitors treating erectile dysfunction work by which mechanism?

PDE5 inhibitors treating erectile dysfunction work by which mechanism?

• A. Directly stimulate testosterone production
• B. Block adrenergic receptors in the penis
• C. Increase calcium influx into smooth muscle
• D. Inhibition of phosphodiesterase-5 leading to increased cGMP and smooth muscle relaxation

Answer: (D)

PDE5 inhibitors work by enhancing the nitric oxide–cGMP pathway to promote smooth muscle relaxation in the penis. During sexual arousal, nitric oxide is released and activates guanylate cyclase, raising cGMP levels. cGMP causes the penile smooth muscle to relax, increasing blood flow and leading to an erection. PDE5 normally breaks down cGMP; blocking PDE5 keeps cGMP elevated longer, amplifying and prolonging the relaxation response in response to sexual stimulation. Directly stimulating testosterone production doesn’t acutely trigger the vascular changes needed for erection. Blocking adrenergic receptors isn’t the mechanism here, as it doesn’t specifically boost the NO–cGMP relaxation pathway. Increasing calcium influx would promote contraction, not relaxation, whereas PDE5 inhibitors reduce the signaling that leads to contraction, allowing prolonged relaxation and improved erection in response to arousal.

PDE5 inhibitors work by enhancing the nitric oxide–cGMP pathway to promote smooth muscle relaxation in the penis. During sexual arousal, nitric oxide is released and activates guanylate cyclase, raising cGMP levels. cGMP causes the penile smooth muscle to relax, increasing blood flow and leading to an erection. PDE5 normally breaks down cGMP; blocking PDE5 keeps cGMP elevated longer, amplifying and prolonging the relaxation response in response to sexual stimulation.

Directly stimulating testosterone production doesn’t acutely trigger the vascular changes needed for erection. Blocking adrenergic receptors isn’t the mechanism here, as it doesn’t specifically boost the NO–cGMP relaxation pathway. Increasing calcium influx would promote contraction, not relaxation, whereas PDE5 inhibitors reduce the signaling that leads to contraction, allowing prolonged relaxation and improved erection in response to arousal.