alone. The safety of regimens containing bedaquiline plus delamanid may be substantially improved if clofazimine can be omitted. @ERSpublications Clofazimine prolongs the QT interval and can potentiate the QT effects of other MDR-TB drugs http://ow.ly/70My302XuKm Robert S. Wallis Aurum Institute, Johannesburg, South Africa. Correspondence: Robert S. Wallis, Aurum Institute, 29 Queens Rd, Parktown 2193, Johannesburg, South Africa. E-mail: rwallis@auruminstitute.org Received: June 19 2016 | Accepted after revision: July 26 2016 Conflict of interest: None declared. References 1 Tadolini M, Lingtsang RD, Tiberi S, et al. First case of extensively drug-resistant tuberculosis treated with both delamanid and bedaquiline. Eur Respir J 2016; 48: 935–938. 2 Fridericia LS. The duration of systole in an electrocardiogram in normal humans and in patients with heart disease. 1920. Ann Noninvasive Electrocardiol 2003; 8: 343–351. 3 Deltyba summary of product characteristics. Report number WC500166232. European Medicines Agency 2015. www.ema.europa.eu/docs/en_GB/document_library/EPAR_-_Product_Information/human/002552/WC500166232. pdf Date last accessed: July 12, 2016. 4 Dannemann B, Bakare N, De Marez T, et al. QTcF prolongation in a phase II trial of TMC207 plus background regimen as treatment for MDR-TB: effect of co-administration of clofazimine. ICAAC 2012; 52: A1259. 5 Everitt D. Clofazimine in clinical trials for tuberculosis. Resurrecting clofazimine. www.resisttb.org/wp-content/ uploads/2013/08/Global-Alliance-Clinical-Work-with-Clofazimine.pdf Date last accessed: July 12, 2016. 6 Sanguinetti MC, Tristani-Firouzi M. hERG potassium channels and cardiac arrhythmia. Nature 2006; 440: 463–469. 7 Hedley PL, Jørgensen P, Schlamowitz S, et al. The genetic basis of long QT and short QT syndromes: a mutation update. Hum Mutat 2009; 30: 1486–1511. 8 S7B Nonclinical evaluation of the potential for delayed ventricular repolarization (QT interval prolongation) by human pharmaceuticals. Report number UCM074963. US FDA 2005. www.fda.gov/downloads/drugs/ guidancecomplianceregulatoryinformation/guidances/ucm074963.pdf Date last accessed: July 12, 2016. 9 Vicente J, Johannesen L, Mason JW, et al. Comprehensive T wave morphology assessment in a randomized clinical study of dofetilide, quinidine, ranolazine, and verapamil. J Am Heart Assoc 2015; 4: pii: e001615. 10 Diacon AH, Dawson R, von Groote-Bidlingmaier F, et al. Bactericidal activity of pyrazinamide and clofazimine alone and in combinations with pretomanid and bedaquiline. Am J Respir Crit Care Med 2015; 191: 943–953. 11 Choudhri SH, Harris L, Butany JW, et al. Clofazimine induced cardiotoxicity – a case report. Lepr Rev 1995; 66: 63–68. Eur Respir J 2016; 48: 1526–1527 | DOI: 10.1183/13993003.01207-2016 | Copyright ©ERS 2016 From the authors: We read with great interest the comments by R.S. Wallis on our article describing the first case of extensively drug-resistant tuberculosis (XDR-TB) treated with both delamanid and bedaquiline [1], as recommended by the European Respiratory Society hosted TB Consilium experts [2, 3]. The patient developed QTc (corrected QT or the measure of time between the start of Q wave and the end of T wave in the heart’s electrical cycle (ECG)) prolongation a few days after beginning treatment, that included not only the two new anti-TB drugs but also clofazimine (which, according to Wallis, may have played a role in QTc prolongation). Clofazimine-related cardiotoxicity has been described in a single case-report on an Indian male with leprosy with electrolyte abnormalities treated with clofazimine for 11 months [4]. We agree that there are ongoing safety concerns about QTc prolongation when clofazimine is combined with bedaquiline; safety data remains sparse, although serious life-threatening arrhythmias resulting from this combination have not been described yet. Our patient had XDR-TB with a single certified active drug, clofazimine, which was the rationale for its inclusion in the salvage regimen. Given the fairly sudden rise in QTc within a week of starting the combination, the TB Consilium experts considered bedaquiline as the culprit for the adverse event. Clofazimine, in fact, requires several weeks to reach the steady state due to its peculiar pharmacokinetics, while bedaquiline at that time was being loaded and, considering its long half-life, the experts recommended to stop it. The patient presented with hypokalaemia during that period, which may have 1527