Is clonazepam (Klonopin) safe to prescribe to patients with long QT syndrome?

Clonazepam and Long QT Syndrome

Clonazepam does not prolong the QT interval and is safe to prescribe in patients with long QT syndrome, unlike certain other psychotropic medications that must be strictly avoided in this population.

Key Safety Distinction

• Benzodiazepines, including clonazepam, are not associated with QT prolongation and do not appear on lists of medications that cause torsades de pointes 1, 2

• The critical medications to avoid in long QT syndrome include certain antidepressants (particularly citalopram, tricyclics, and some SSRIs), antipsychotics (haloperidol, phenothiazines), antibiotics (macrolides, quinolones), antiemetics, and class IA/III antiarrhythmics 1, 2, 3, 4

Medications That ARE Contraindicated in Long QT Syndrome

The AHA/ACC/HRS guidelines provide a Class III: Harm recommendation stating that QT-prolonging medications are potentially harmful in patients with long QT syndrome 1

Specific high-risk psychotropic agents to avoid:

• Citalopram is specifically contraindicated in long QT syndrome, as it can cause QT prolongation, torsades de pointes, ventricular tachycardia, and sudden death at daily doses exceeding 40 mg/d 1, 4

• Tricyclic antidepressants and certain SSRIs (particularly paroxetine, fluvoxamine, sertraline when combined with other QT-prolonging agents) carry risk 1, 3

• Antipsychotics including haloperidol and phenothiazines are documented QT-prolonging agents 3

• ADHD medications (stimulants and non-stimulants) have been associated with increased risk of syncope/cardiac arrest in long QT syndrome patients, particularly in males 1, 2

Clinical Management Algorithm

When prescribing any medication to long QT syndrome patients:

1. Check www.crediblemeds.org for the most current list of QT-prolonging medications before prescribing 1, 5

2. Maintain strict electrolyte balance - hypokalemia and hypomagnesemia from any cause (diuretics, gastrointestinal illness) can precipitate torsades de pointes 1, 2, 3

3. Monitor for drug-drug interactions - combining multiple medications that individually have modest QT effects can be dangerous 1, 6

4. Baseline and follow-up ECGs are recommended when prescribing any medication with potential cardiac effects, even if not classically QT-prolonging 6, 4

Common Pitfall

Real-world data shows that 60% of long QT syndrome patients receive at least one QT-prolonging medication after diagnosis, with the most common being antibiotics (34.1%), proton-pump inhibitors (15.0%), and antidepressants (12.0%) 5. This highlights the critical need for heightened awareness when prescribing to this population.

Bottom Line for Clonazepam

Clonazepam can be safely prescribed for anxiety or other indications in long QT syndrome patients, as it does not affect cardiac repolarization. However, if treating anxiety or depression, avoid SSRIs with known QT effects (especially citalopram) and consider alternative agents with better cardiac safety profiles 1, 4.