Therapeutic drug monitoring: how to improve drug dosage and patient safety in tuberculosis treatment

In this article we describe the key role of tuberculosis (TB) treatment, the challenges (mainly the emergence of drug resistance), and the opportunities represented by the correct approach to drug dosage, based on the existing control and elimination strategies. In this context, the role and contribution of therapeutic drug monitoring (TDM) is discussed in detail. Treatment success in multidrug-resistant (MDR) TB cases is low (62%, with 7% failing or relapsing and 9% dying) and in extensively drug-resistant (XDR) TB cases is even lower (40%, with 22% failing or relapsing and 15% dying). The treatment of drug-resistant TB is also more expensive (exceeding €50,000 for MDR-TB and €160,000 for XDR-TB) and more toxic if compared to that prescribed for drug-susceptible TB. Appropriate dosing of first- and second-line anti-TB drugs can improve the patient's prognosis and lower treatment costs. TDM is based on the measurement of drug concentrations in blood samples collected at appropriate times and subsequent dose adjustment according to the target concentration. The 'dried blood spot' technique offers additional advantages, providing the rationale for discussions regarding a possible future network of selected, quality-controlled reference laboratories for the processing of dried blood spots of difficult-to-treat patients from reference TB clinics around the world.