What is the effect of combining antihypertensives with grapefruit?

• A. Increased efficacy
• B. Decreased efficacy
• C. No effect
• D. Variable effect based on individual response

Answer: (B)

Combining antihypertensives with grapefruit can lead to decreased efficacy of the medication due to the interaction between certain drugs and components found in grapefruit. Grapefruit contains compounds called furanocoumarins that inhibit the activity of the cytochrome P450 3A4 (CYP3A4) enzyme in the intestine. This enzyme plays a critical role in metabolizing many medications, including certain antihypertensives.

When CYP3A4 is inhibited, the metabolism of antihypertensives that are normally broken down by this enzyme is reduced, which can lead to higher concentrations of the drug in the bloodstream. This unexpected increase in drug levels can sometimes result in adverse effects rather than therapeutic benefits, leading to a situation where the desired lowering of blood pressure may not occur effectively. Therefore, the expected therapeutic outcome of these antihypertensive medications can be compromised when taken with grapefruit, resulting in decreased overall efficacy of the treatment.