Clinical practice includes contributions from physicians, pharmacists, NPs, and physician assistants. Drug safety considerations are of considerable importance. This article discusses drug-induced proarrhythmia, with a specific focus on torsades de pointes, a polymorphic ventricular tachycardia that typically occurs in self-limiting bursts that can lead to dizziness, palpitations, syncope, and seizures, but on rare occasions can progress to ventricular fibrillation and sudden cardiac death. A dedicated clinical pharmacology study conducted during a drug's clinical development program has assessed its propensity to induce torsades using prolongation of the QT interval as seen on the ECG as a biomarker.Identification of QT-interval prolongation does not necessarily prevent a drug from receiving marketing approval if its overall benefit-risk balance is favorable, but, if approved, a warning is placed in its prescribing information. This article explains why drugs can have a proarrhythmic propensity.