Can Kava or L-Theanine Prolong the QT Interval?
Neither kava nor L-theanine are recognized as QT-prolonging agents in established cardiology guidelines or comprehensive drug databases that track QT prolongation. 1
Evidence Review
Established QT-Prolonging Drugs
The ACC/AHA/ESC guidelines and comprehensive registries (www.torsades.org and www.qtdrugs.org) maintain updated lists of medications known to prolong the QT interval and cause torsades de pointes. 1 These lists include:
- Antiarrhythmics: disopyramide, dofetilide, ibutilide, procainamide, quinidine, sotalol, amiodarone 1
- Antimicrobials: clarithromycin, erythromycin, halofantrine, pentamidine, sparfloxacin 1
- Antipsychotics: chlorpromazine, haloperidol, mesoridazine, thioridazine, pimozide 1
- Other agents: methadone, cisapride, domperidone, droperidol 1
Kava and L-Theanine Status
Neither kava nor L-theanine appear on any of these established lists of QT-prolonging medications. 1, 2
The available literature on kava describes its pharmacological mechanisms as including sodium channel blockade, GABA receptor modulation, calcium channel effects, and monoamine oxidase B inhibition, but does not identify QT prolongation as a known effect. 3 The primary safety concerns with kava relate to hepatotoxicity and kava dermopathy with chronic high-dose use, not cardiac conduction abnormalities. 3
No published evidence exists linking L-theanine to QT interval prolongation or cardiac arrhythmias. This amino acid is not mentioned in any cardiology guidelines or drug safety databases regarding QT prolongation. 1, 2, 4
Clinical Implications
When to Monitor QT Interval
QT monitoring is indicated when patients are exposed to recognized QT-prolonging drugs, particularly when risk factors are present: 1, 4
- Female gender 1
- Age >65 years 4
- Hypokalemia or hypomagnesemia 1
- Baseline QT prolongation 1
- Concomitant use of multiple QT-prolonging medications 1, 5
- Structural heart disease or left ventricular hypertrophy 1
Practical Recommendation
Based on current evidence, routine QT monitoring is not warranted for patients taking kava or L-theanine alone, as these agents are not established QT-prolonging drugs. 1, 2 However, if patients are taking these supplements alongside known QT-prolonging medications, standard monitoring protocols for the established QT-prolonging agent should be followed. 1, 5
Important Caveats
The absence of kava and L-theanine from QT-prolonging drug lists does not guarantee absolute safety, as herbal supplements and amino acids are less rigorously studied than pharmaceutical agents. 3 However, clinical decision-making should be based on established evidence, and there is no credible evidence linking either substance to clinically significant QT prolongation or torsades de pointes. 1, 2