A 68-year-old male, Mr. Robert Jones (CrCl 75 mL/min), is admitted with an acute deep vein thrombosis and started on rivaroxaban 15 mg twice daily for 21 days, followed by 20 mg once daily. He has a history of hypertension, type 2 diabetes, and benign prostatic hyperplasia. His current medications include ramipril 10 mg daily, metformin 1000 mg twice daily, and tamsulosin 0.4 mg daily. Three days into his rivaroxaban therapy, he develops a respiratory infection and is prescribed ciprofloxacin 500 mg twice daily. What adjustment, if any, should be made to Mr. Jones' rivaroxaban therapy?

Question: A 68-year-old male, Mr. Robert Jones (CrCl 75 mL/min), is admitted with an acute deep vein thrombosis and started on rivaroxaban 15 mg twice daily for 21 days, followed by 20 mg once daily. He has a history of hypertension, type 2 diabetes, and benign prostatic hyperplasia. His current medications include ramipril 10 mg daily, metformin 1000 mg twice daily, and tamsulosin 0.4 mg daily. Three days into his rivaroxaban therapy, he develops a respiratory infection and is prescribed ciprofloxacin 500 mg twice daily. What adjustment, if any, should be made to Mr. Jones' rivaroxaban therapy?

Answer options:

• No adjustment is needed, as ciprofloxacin does not significantly interact with rivaroxaban.
• Decrease rivaroxaban dose to 10 mg once daily while on ciprofloxacin. ✅ Switch to dalteparin for the duration of ciprofloxacin therapy.
• Increase rivaroxaban monitoring with daily anti-Xa levels.

Correct answer: Switch to dalteparin for the duration of ciprofloxacin therapy.

Explanation: Ciprofloxacin is a dual inhibitor of CYP3A4 and P-gp, both of which are involved in the metabolism/transport of rivaroxaban. Co-administration can significantly increase rivaroxaban exposure, leading to an increased risk of bleeding. As rivaroxaban is currently dosed for acute treatment where efficacy is critical, switching to an alternative anticoagulant (e.g., LMWH like dalteparin) is the safest approach during concomitant ciprofloxacin use.