American Board of Family Medicine (ABFM) Practice Exam

Which anti-hypertensive medication's effectiveness may be affected in a patient taking PPI, amoxicillin, and clarithromycin?

1. Clonidine transdermal (Catapres-TTS)

2. Hydrochlorothiazide

3. Metoprolol tartrate (Lopressor)

4. Amlodipine (Norvasc)

The correct answer is: Amlodipine (Norvasc)

The effectiveness of amlodipine, a calcium channel blocker used for hypertension, can be influenced by drug interactions that might occur with other medications. Proton Pump Inhibitors (PPIs) such as those prescribed alongside amoxicillin and clarithromycin can impact the absorption and metabolism of certain medications. Specifically, PPIs may affect gastric pH and alter the bioavailability of drugs that rely on certain pH levels for optimal absorption. Amlodipine is among those drugs, as its absorption can be slightly altered by changes in gastric acidity. While it remains effective, the extent of its effect might be less predictable in the presence of a PPI, potentially leading to suboptimal blood pressure control in some patients. In contrast, medications like clonidine transdermal, hydrochlorothiazide, and metoprolol tartrate generally do not exhibit the same level of interaction with PPIs, amoxicillin, and clarithromycin. Their mechanisms of action and pharmacokinetic profiles make them less susceptible to changes in gastric pH or absorption rates caused by PPIs, thereby maintaining their effectiveness regardless of concurrent PPI use. Thus, the impact on amlodipine highlights a relevant clinical consideration when managing patients on multiple medications,