Use of therapeutic drug monitoring for multidrug-resistant tuberculosis patients.

STUDY OBJECTIVES Therapeutic drug monitoring (TDM) is the process of obtaining the serum concentration of a medication and modifying the dose based on the results. Little is known about the application of TDM in the treatment of patients with multidrug-resistant (MDR) tuberculosis (TB) in clinical practice. This study characterized how TDM was applied in the management of MDR TB patients, and examined the clinical indications for ordering TDM, the process for obtaining drug concentrations, and the clinician response to the drug concentrations. DESIGN In a retrospective study, we compared the clinical and demographic characteristics of MDR TB patients who received TDM with those who did not. The clinical application of TDM also was described in patients who received TDM. SETTING A municipal TB control program. PATIENTS OR PARTICIPANTS Patients in whom TB was diagnosed that was caused by an isolate resistant to at least isoniazid and rifampin, and who received treatment for TB in one of the health department chest clinics between July 1, 1993, and August 31, 1997, were studied. RESULTS Forty-nine patients receiving TDM had a longer time to culture conversion and treatment duration, more pulmonary TB in combination with an extrapulmonary site, drug resistance, and visits to the health department clinics (p < 0.05) than the 60 patients without TDM. Of the 49 patients who had initial TDM, 73.5% of them had the reason for being tested specified. A total of 85.7% of initial TDM results were collected at the appropriate time of blood sampling. Clinician response to TDM results varied with the drug that was being tested. CONCLUSIONS The use of TDM depended largely on the patient's clinical presentation. Site-specific guidelines on the use of TDM for managing TB patients may maximize the benefit of TDM.