A client with trigeminal neuralgia is being treated with carbamazepine (Tegretol). Which laboratory result would indicate that the client is experiencing an adverse reaction to the medication?

Carbamazepine, a medication used to treat trigeminal neuralgia, can have significant adverse effects on the body, one of which includes its impact on blood cell production. Monitoring the white blood cell count is essential because carbamazepine can cause bone marrow suppression, leading to a decreased number of white blood cells, a condition known as leukopenia. A white blood cell count of 3000 cells/mm³ is indicative of this adverse reaction, as normal ranges typically fall between 4,500 and 11,000 cells/mm³. This low count can increase the risk of infections and signal the healthcare provider to reevaluate the medication or perform further investigations.

On the other hand, the other laboratory results listed do not indicate adverse reactions associated with carbamazepine. A sodium level of 140 mEq/L is within the normal range, a uric acid level of 5.0 mg/dL is also normal, and a BUN level of 15 mg/dL indicates normal kidney function. These values do not suggest any acute or chronic adverse reactions to carbamazepine, which reinforces why the abnormal white blood cell count is the primary concern in this scenario.