Objective: The actual prevalence of drug induced QTc prolongation in clinical practice is unknown. Our
objective was to determine the occurrence and characteristics of drug-induced QT prolongation in several common
clinical practices. Additionally, a subgroup of patients treated with dextropropoxyphene of particular interest for the
regulatory authority was analysed.
Research Design and Methods: Medical history and comorbidities predisposing to QT interval prolongation were
registered for 1270 patient requiring medical assistance that involved drug administration. Three ionograms and ECGs
were performed: baseline, intra- and after treatment; QT interval was corrected with Bazzet formula.
Results: Among patients, 9.9% presented QTc >450/470 ms, 3% QTc > 500 ms, 12.7% ΔQTc >30 ms and 5.2% ΔQTc
>60 ms. QTc prolongation associated with congestive heart failure, ischemic cardiopathy, diabetes, renal failure,
arrhythmias, hypothyroidism, and bradycardia. At univariate analysis, clarithromycin, haloperidol, tramadol, amiodarone,
glyceryl trinitrate, amoxicillin + clavulanic acid, amoxicillin + sulbactam, ampicillin + sulbactam, fentanyl, piperacillin +
tazobactam, and diazepam prolonged QTc. Prolongation remained significantly associated with furosemide,
clarithromycin, glyceryl trinitrate and betalactamase inhibitors after multivariate analysis.
Conclusion: QT interval prolongation in everyday practice is frequent, in association to clinical factors and drugs that can
be easily identified for monitoring and prevention strategies.