Potency and Efficacy of Medications

Potency and efficacy are two of the most misunderstood concepts in the area of drug use. Many overdoses occur because the potency of the newly purchased drug is higher than that of the previously used drug. These concepts apply to drugs of abuse as well as over-the-counter medications.

Steven has a headache. He reaches for some pain relievers in his medicine cabinet. He finds two bottles: acetaminophen (325 mg) and ibuprofen (200 mg). The instructions for the acetaminophen say take 2 tablets

(650 mg total). The instructions for the ibuprofen say take 2 tablets (400 mg total). Steven assumes that because the dose is higher for the acetaminophen, it must work better.

To assist Steven with making an educated decision about which medication to take, complete the following:

What are potency and efficacy, and how are they different?

What other factors might influence Steven's decision?