Linezolid tolerability in multidrug-resistant tuberculosis: a retrospective study.

Linezolid is used off-label to treat multidrug-resistant (MDR) and extensively drug-resistant (XDR) tuberculosis (TB) [1, 2]. Recently, two systematic reviews and meta-analyses pointed out its promising efficacy [3, 4]. However, linezolid toxicity may outweigh its potential benefits. Indeed, adverse events were notified in almost 60% of the treated cases, with a high incidence of severe events such as anaemia, peripheral neuropathy, optic neuritis, and thrombocytopenia. Decreased linezolid doses were associated with significantly lowered toxicity [5]. Furthermore, therapeutic drug monitoring (TDM) has increasingly been recognised as an asset in the field of TB treatment [6, 7]. TDM may assess individual linezolid exposure, especially since the drug shows a large inter-individual variability [8] and important pharmacological interactions were observed [6]. However, there is no clear association between linezolid exposure and adverse events. Drug exposure is not routinely evaluated, either in prospective studies or in routine care. Unfortunately, TDM is not routinely incorporated into the study designs of research upon MDR-TB and linezolid [9, 10]. Therefore, we aimed to retrospectively investigate linezolid safety and tolerability in relation to linezolid exposure in MDR-TB patients.