OBJECTIVE: to verify the influence of antimalarial drugs (chloroquine and hydroxychloroquine) on the QT interval of the electrocardiogram. METHODS: we studied 46 rheumatic patients (42 using chloroquine and 4 using hydroxychloroquine), both taking the usual doses of such drugs (7 mg/kg/day of hydroxychloroquine and 4 mg/kg/day of chloroquine) except for those with osteoarthritis (n = 8) who used half of the dose. Electrocardiogram was performed in all patients with measurements of QTc interval. Patients with abnormal results were advised to withdraw the medication and repeat the ECG within two weeks. RESULTS: QTc interval prolongation was observed in 17.39% of the patients. Such abnormalities were not related to dose (p = 0.574), type of antimalarial drug (p = 0.452) and duration of drug use (p = 0.09). All patients with abnormal results, except for one, repeated the ECG with return to normal values. CONCLUSIONS: we concluded that patients taking chloroquine may have QTc prolongation as an adverse effect.
antimalarial drugs; chloroquine; hydroxychloroquine; long QT; arthritis
