Prescribing Safety Assessment (PSA) Practice Exam

What is the primary action of p450 inhibitors?

1. They decrease the efficacy of other drugs

2. They increase the drug levels of other drugs

3. They have no effect on drug levels

4. They promote drug metabolism

The correct answer is: They increase the drug levels of other drugs

The primary action of P450 inhibitors is to increase the drug levels of other drugs. These inhibitors work by blocking or reducing the activity of the cytochrome P450 enzyme system, which is responsible for the metabolism of many medications. When the activity of these enzymes is inhibited, the metabolism of drugs that are substrates for these enzymes decreases, leading to higher concentrations of those drugs in the bloodstream. As a result, the therapeutic effects may be amplified, and the risk of toxicity can increase if the doses are not adjusted accordingly. This interaction underscores the importance of monitoring and potentially adjusting the dosages of concurrently prescribed medications when a P450 inhibitor is introduced to a treatment regimen. In contrast, the other options do not accurately describe the mechanism of action associated with P450 inhibitors, as they do not directly contribute to a decrease in drug efficacy, have no effect on drug levels, or promote drug metabolism.