Question

Which of the following statements is NOT TRUE for effect of co-administration of erythromycin with cyclosporine?

• A. \( \text{It decreases its metabolism} \)
• B. \( \text{It increases its gastrointestinal absorption} \)
• C. \( \text{It increases its toxicity} \)
• D. \( \text{It increases its clearance} \)

Hint:

Remember that enzyme inhibitors (like erythromycin on CYP3A4) generally lead to decreased metabolism and increased levels/toxicity of the substrate drug (cyclosporine in this case). Clearance is usually reduced, not increased.

Answer 1

The Correct Option is D

Erythromycin is a macrolide antibiotic that inhibits cytochrome P450 enzymes, particularly CYP3A4, which is a major enzyme involved in the metabolism of cyclosporine. By inhibiting CYP3A4, erythromycin decreases the metabolism of cyclosporine, leading to increased levels of cyclosporine in the body and potentially increased toxicity. Erythromycin does not typically increase the gastrointestinal absorption of cyclosporine. The increased levels of cyclosporine due to reduced metabolism can lead to increased toxicity. Therefore, the statement that is NOT TRUE is that erythromycin increases the clearance of cyclosporine; in fact, it decreases its clearance by inhibiting its metabolism.