Which of the following drugs is a HMG-CoA reductase inhibitor?

HMG-CoA reductase inhibitors, commonly known as statins, work by blocking the enzyme HMG-CoA reductase, which is a key player in the cholesterol synthesis pathway in the liver. By inhibiting this enzyme, statins effectively reduce the production of cholesterol, leading to decreased levels of low-density lipoprotein (LDL) cholesterol in the bloodstream. This mechanism not only helps in managing hyperlipidemia but also contributes to cardiovascular risk reduction.

Statins are particularly beneficial for patients with elevated LDL levels and those with a history of cardiovascular disease. In addition to lowering cholesterol, they can have other favorable effects on the vascular endothelium and potentially reduce inflammation.

The other choices do not fall under the category of HMG-CoA reductase inhibitors or have different mechanisms. For example, trimethoprim is an antibiotic that inhibits bacterial dihydrofolate reductase, penicillin is a β-lactam antibiotic that interferes with bacterial cell wall synthesis, and carvedilol is a non-selective beta-blocker and alpha-1 blocker used primarily for hypertension and heart failure. Therefore, statins stand out as the correct answer for this question regarding HMG-CoA reductase inhibitors.