From the Guidelines
Drugs that prolong the QT interval, such as Class IA antiarrhythmics (quinidine, procainamide, disopyramide), Class III antiarrhythmics (amiodarone, sotalol, dofetilide), and certain antibiotics (macrolides, fluoroquinolones), are contraindicated in torsades de pointes. These medications should be avoided because torsades de pointes is a specific type of polymorphic ventricular tachycardia associated with QT prolongation, and these drugs can further extend the QT interval, potentially worsening the arrhythmia or triggering recurrent episodes 1.
Key Points to Consider
- The removal of the offending agent is indicated in patients with drug-induced long QT syndrome, as stated in the guidelines 1.
- Temporary pacing is highly effective in managing torsades de pointes that is recurrent after potassium repletion and magnesium supplementation 1.
- Intravenous magnesium can suppress episodes of torsades de pointes without necessarily shortening QT, even when serum magnesium is normal 1.
- The 2015 ESC guidelines for the management of patients with ventricular arrhythmias and the prevention of sudden cardiac death also support the avoidance of QT-prolonging drugs in patients with torsades de pointes 2.
Recommended Approach
- Avoid the use of QT-prolonging drugs, such as Class IA and III antiarrhythmics, and certain antibiotics, in patients with torsades de pointes.
- Instead, focus on the immediate treatment of torsades de pointes, which typically includes intravenous magnesium sulfate, correction of electrolyte abnormalities, removal of offending agents, and temporary cardiac pacing if necessary.
- Consider the underlying mechanism of torsades de pointes and the potential risks of using QT-prolonging drugs in these patients, as highlighted in the guidelines 1, 2.
From the FDA Drug Label
TIKOSYN is contraindicated in patients with congenital or acquired long QT syndromes, and in patients with a history of Torsade de Pointes 3. The drug dofetilide (TIKOSYN) is contraindicated in patients with a history of Torsades de Pointes (TdP).
- Key points to consider:
- Contraindication: TIKOSYN is contraindicated in patients with a history of Torsade de Pointes.
- Caution with other medications: The use of TIKOSYN with other drugs that prolong the QT interval is not recommended.
From the Research
Torsades de Pointes (TdP) Contraindicated Drugs
- Quinidine is a drug that is contraindicated in Torsades de Pointes (TdP) as it can precipitate this life-threatening arrhythmia 4, 5.
- Disopyramide, a type IA antiarrhythmic agent, is also known to cause TdP and should be avoided in patients at risk of this condition 4, 5.
- Other antiarrhythmic agents, such as procainamide and phenothiazines, have been associated with TdP and should be used with caution 5.
- Dofetilide, an antiarrhythmic agent, can also induce TdP, especially when used with concomitant drugs that prolong the QT interval or in patients with renal dysfunction 6.
- Thioridazine, an antipsychotic drug, has been reported to cause TdP and should be avoided in patients with a history of QT interval prolongation 5.
Mechanism and Risk Factors
- The mechanism of TdP involves prolongation of the QT interval, which can be caused by various drugs, including antiarrhythmic agents, antipsychotics, and antibiotics 7, 8.
- Risk factors for TdP include electrolyte imbalance (hypokalemia, hypomagnesemia), slow heart rate, and concomitant use of drugs that prolong the QT interval 4, 7.
Management Strategies
- Treatment of TdP involves discontinuation of the offending drug, correction of electrolyte abnormalities, and administration of intravenous magnesium sulfate 4, 7.
- Overdrive pacing and cautious isoproterenol administration can also be used to manage TdP 5.
- Potassium and magnesium repletion are essential in abolishing drug-induced TdP 5.