Erectile Dysfunction medications such as sildenafil, tadalafil, and vardenafil belong to which class of drugs?

• A. PDE-5 inhibitors
• B. Beta blockers
• C. ACE inhibitors
• D. Calcium channel blockers

Answer: (A)

These medications are phosphodiesterase type-5 inhibitors. They boost erections by blocking the enzyme that normally breaks down cGMP, a molecule that promotes smooth muscle relaxation in the penis after sexual stimulation. When you’re aroused, nitric oxide releases and increases cGMP, which relaxes the smooth muscle of the corpora cavernosa and allows more blood to fill the penis. PDE-5 would normally shorten this signal by degrading cGMP, so inhibiting PDE-5 keeps cGMP around longer and enhances the erectile response in the presence of stimulation. They require sexual arousal to work and do not cause an erection on their own. Important interactions include nitrates, which can cause dangerous drops in blood pressure, and various other meds that can affect blood pressure or alertness. These other drug classes act through different mechanisms—beta blockers affect heart rate and contractility, ACE inhibitors target the renin-angiotensin system, and calcium channel blockers reduce calcium entry in smooth muscle—so they don’t work by preserving cGMP in penile tissue.