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- Many meds cause a prolonged QT; this is due to a mutation of a gene that codes for the rapid component of the K+ rectifying current. This leads to problems with repolarization.
- Drugs causing prolonged QT with THERAPEUTIC doses include: antiarrhythmics (quinidine, procainamide, amiodarone, sotalol, and dofetilide)
- Other agents that cause prolonged QT with ELEVATED serum concentrations include: antihistamines, some antibiotics and psychiatric meds (amitriptyline, cisapride, erythromycin, pimozide, thioridazine, SSRIs, trazodone, and moxifloxacin)
- Use caution when combining medications from either, or both groups!
Other factors that are associated with prolonged QT include: bradycardia, female sex, genetics, and electrolyte abnormalities.
References
Kannakeril PJ, Roden DM. Drug-Induced long QT and torsade de pointes: recent advances. Current opinions in cardiology. Jan 2007;22(1):39-43.
Horn JR, Hansten PD. Drug Interactions and QT Interval Prolongation. Pharmacy Times Dec 2004. pp66.