INTRODUCTION:The continuing spread of multidrug-resistant tuberculosis (MDR TB) is one of the most urgent and difficult challenges facing global TB control.

The aim :To evaluate the impact of adverse effects of 2nd line anti-TB drugs on adherence and efficacy of treatment of MDR TB.

Methodology : Retrospective study including cases of MDR TB followed in our department from January 2010 to December 2020.

Results :A total of 101 patients were included in the study. The majority of patients were male (71.3%), and their mean age was 37 years . The most common risk factors of TB are smoking (70%), chronic alcoholism (34%), incarceration (17%) and drug addiction (9%). Among our patients, 95% had a pulmonary TB and 64% had secondary resistance. the average treatment time was 18 months (-+ 6 months). Treatment-related side effects were found in 88% of cases. Absence of compliance with treatment was found in 33 % of cases .A therapeutic failure is observed in 26% of cases. The most important adverse effects associated with poor compliance were nephrotoxicity (p=0.01), psychiatric disorders (p=0.07), hypothyroidism (p=0.03), hyperuricemia (p<0.001) and visual disturbances (p=0.03). Nephrotoxicity (p<0.001), vomiting (p=0.016), epigastralgia (p<0.001) and peripheral neuropathy (p=0.004) were the adverse events associated with therapeutic failure.

Conclusion :Side effects related to treatment are responsible for poor compliance and subsequent therapeutic failure, in particular nephrotoxicity, gastric disorders and neuro-psychiatric disorders