Putting in Harm to cure: Drug related adverse events do not affect outcome of patients receiving treatment for Multidrug-Resistant Tuberculosis

<b>Rationale:</b> Treatment of multi-drug resistant Tuberculosis (MDR-TB) is challenging because it mostly relies on drugs with low efficacy and great toxicity. <b>Objectives:</b> To describe the frequency and type of adverse drug reactions in a cohort of MDR-TB patients. <b>Methods:</b> We conducted a retrospective study in a cohort of MDR-TB patients enrolled in a referral center in Italy from 2008 to 2016. <b>Results:</b> Seventy-four MDR-TB patients ( mean age 32 years, 58.1% males, 2 XDR, 12 pre-XDR TB) were evaluated. Median length of treatment duration was 20 months (IQR 14-24). Treatment outcome was successful in 57 patients (77%; 51 cured, 6 treatment completed); one patient died and one failed (2.7% overall); 15 patients were lost to follow-up (20.3%). Sixty-six (89.2%) presented adverse drug reactions during the whole treatment period. Total number of adverse drug reactions registered was 409. Three hundred forty-six (84.6%) were classified in adverse events (AEs) and 63 (15.4%) were serious AEs (SAEs). Factors associated with unsuccessful treatment outcomes were smoking (p=0.039), alcohol abuse (p= 0.005) and homeless condition (p= 0.044). Neither the number of antitubercular drugs used in different combinations nor the number of AEs showed significant impact on outcome. Patients who completed the treatment experienced a greater number of AEs and SAEs (p &lt; 0.001) if compared to lost to follow-up patients. <b>Conclusions:</b> Our data demonstrate that, despite the high frequency of adverse drug reactions and long term therapy, the clinical management of MDR-TB patients in a referral center could reach successful treatment according to WHO target.