A 60-year-old male Suresh is hospitalized with muscle pain, fatigue and dark urine. His past medical history is significant for stable angina. The patient’s medications include atenolol, atorvastatin, and aspirin. His urine dipstick test is positive for blood but urine microscopy did not reveal RBCs in the urine. Serum creatinine kinase was significantly raised in this person. The addition of which of the following medications is most likely to have precipitated this patient’s condition?

**Core Concept:** Muscle pain, fatigue, and dark urine can be clinical manifestations of rhabdomyolysis, which is a condition characterized by the breakdown of muscle cells leading to the release of myoglobin and creatinine kinase (CK) into the bloodstream. In this scenario, the patient is on atorvastatin, a statin, and has experienced a recent muscle injury. Muscle injury can cause an increase in CK levels.

**Why the Correct Answer is Right:** The correct answer is C, D-L Myoglobinuria, which is a rare complication of statin therapy, particularly with high-dose statins. In this patient, the combination of statin therapy, specifically atorvastatin, and recent muscle injury (as evidenced by muscle pain, fatigue, and elevated CK levels) has led to an increased risk of developing D-L myoglobinuria.

**Why Each Wrong Option is Incorrect:**

A. Atenolol: A beta-blocker, atenolol does not directly cause muscle injury or rhabdomyolysis. It is not the primary cause of the patient's symptoms.

B. ACE inhibitors: ACE inhibitors, such as enalapril or lisinopril, are not implicated in causing D-L myoglobinuria.

D. Rhabdomyolysis: Although rhabdomyolysis can be caused by various factors, it is incorrect to attribute the patient's symptoms to rhabdomyolysis alone without considering the context of statin therapy and muscle injury.

**Clinical Pearl:** D-L myoglobinuria, also known as rhabdomyolysis, is a potential complication of statin therapy, particularly with high-dose statins. It is essential to consider the patient's medication history and recent muscle injury when evaluating for this condition. Promptly discontinuing the offending statin and treating the underlying cause (muscle injury) is crucial in preventing further complications.

✓ Correct Answer: A. Erythromycin