NAPLEX Question of the Week: Potency and Statins

We hear the term "potency" a lot with regards to drug therapy. How can we apply this principle to the exam and ultimately clinical practice?

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You are an internal medicine clinic pharmacist practicing at the VA medical center. During clinic one afternoon an internal medicine resident inquires of you regarding relative potency of various HMG-CoA reductase inhibitors and LDL cholesterol lowering.

Rank the following HMG-CoA reductase inhibitors effects on LDL cholesterol from least to most potent. Assume a 20mg dosage for each agent.

A. Atorvastatin

B. Pravastatin

C. Rosuvastatin

D. Simvastatin

Answer with rationale:

The correct answer is B-D-A-C. HMG-CoA reductase inhibitors (statins) are some of the most prescribed agents in medicine due to their beneficial effects on cholesterol and more importantly outcomes such as nonfatal MI, stroke, and overall mortality. Typically statins are recommended in a number of groups and discussed as "intensity" rather than potency but essentially this is the same idea. Rosuvastatin is the most potent statin followed by atorvastatin, simvastatin, and pravastatin at equivalent doses. High "potent" or intensity statins are recommended for the highest cardiovascular risk groups in order to decrease their risk of morbidity and mortality.

Ranking question are inherently subject to mistakes in selecting the correct order. Be sure and understand exactly what the question is asking. If this question would have been "Rank the following statins in order from lowest to highest dose required to achieve equivalent LDL lowering" then the order would be reversed because Crestor due to its highest potency would require the lowest dose to achieve LDL lowering.

Christopher M. Bland

Clinical Associate Professor, University of Georgia College of Pharmacy

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