Causality, severity, and preventability of adverse drug reactions due to multi-drug therapy in leprosy: evidence from a national level institution in Sri Lanka

Objective This study describes the causality, severity, and preventability of adverse drug reactions (ADR) in patients affected by leprosy treated with multi-drug therapy (MDT) at the dermatology and central leprosy clinics of the National Hospital of Sri Lanka.Methods This cross-sectional analytical study consisted of two components (ret-rospective and prospective). Prospective cases were recruited and followed up for six months. Retrospective data collection was carried out at relevant clinics in the NHSL by extracting data from the clinical records of the patients. When an ADR was suspected, it was confirmed after discussion with the clinic medical officers/consul-tant dermatologist and scored according to the Naranjo ADR probability scale. The intensity of an individual ADR was evaluated using the modified Hartwig and Siegel Severity Assessment Scale, and preventability assessment was performed using the modified Schumock and Thornton scale.Results One hundred and ninety-seven patients were included for ADR attributable to MDT. Approximately 145 patients (73.6%) developed ADR associated with dapsone. Another 50 cases (25.3%) were associated with rifampicin, and 10 (5.1%) were associated with clofazimine. Of the dapsone related 145 ADRs, 59 (40.7%) were definite, 64 (44.1%) were probable, and 22 (15.2%) were possible. Of the rifampicin-related cases, four (8%) were definite, 35 (70%) were probable, and 11 (22%) were possible. The most common adverse drug reactions detected were haemolytic anaemia and hepatic abnormalities due to MDT. Dapsone was discontinued in 40% (59 out of 145) of these patients, while rifampicin was stopped in 8% (4 out of 50) of patients. Clofazimine was not stopped in any of the patients.Conclusions Adverse drug reactions associated with multidrug therapy in leprosy are common among patients diagnosed with leprosy in Sri Lanka. Most ADRs reported in this study were of mild severity and preventable. Careful monitoring and objective scales are needed to identify ADRs at an early stage.