Which of the following medications, carbamazepine (anticonvulsant and mood stabilizer), propranolol (beta-blocker), gabapentin (anticonvulsant), and valproate (anticonvulsant), are known to prolong the QT (quantum time) interval?

QT Prolongation Risk Among Anticonvulsants and Beta-Blockers

Among the medications listed, carbamazepine does NOT prolong the QT interval, propranolol does NOT prolong the QT interval, gabapentin does NOT prolong the QT interval, and valproate does NOT prolong the QT interval. None of these four medications are recognized as QT-prolonging agents in current clinical guidelines.

Evidence-Based Classification

Carbamazepine

• Carbamazepine is explicitly listed as a CYP3A4 inducer that accelerates metabolism of other drugs rather than prolonging QT interval 1
• The European Heart Journal guidelines on psychotropic medications classify mood stabilizers (carbamazepine, lamotrigine, valproate, and lithium) as generally NOT associated with severe arrhythmia 1
• Carbamazepine's primary cardiac concern relates to drug interactions where it reduces effectiveness of other medications, not QT prolongation 1

Propranolol

• Propranolol is not mentioned in any guideline or research evidence as a QT-prolonging agent 1, 2, 3
• Beta-blockers like propranolol are actually recommended as baseline treatment for patients WITH congenital long QT syndrome to reduce arrhythmia risk 3
• No evidence exists linking propranolol to QT interval prolongation in the provided literature

Gabapentin

• Gabapentin (and pregabalin) are classified as anxiolytic agents that do NOT cause QT prolongation 1
• The European Heart Journal specifically notes that benzodiazepines and pregabalin show no changes in QT duration in clinical use, despite in vitro effects on potassium currents 1
• Gabapentin is not listed among QT-prolonging medications in any of the comprehensive drug safety databases reviewed 1

Valproate

• Valproate is explicitly classified among mood stabilizers that have NOT been associated with severe arrhythmia 1
• The European Heart Journal guidelines state that anticonvulsants (including valproate) have generally not been associated with severe arrhythmia 1
• No evidence in the provided literature links valproate to QT prolongation

Clinical Context: Actual QT-Prolonging Medications

To provide perspective, medications that DO prolong QT interval include 1, 2:

• Antiarrhythmics: Amiodarone, sotalol, procainamide, disopyramide, quinidine 1
• Antipsychotics: Thioridazine (25-30 ms), haloperidol (7 ms), ziprasidone (5-22 ms), pimozide (13 ms) 2
• Antidepressants: Tricyclic antidepressants, citalopram, escitalopram 1
• Antiemetics: 5-HT3 antagonists (ondansetron), metoclopramide, domperidone 1, 3
• Antibiotics: Macrolides, fluoroquinolones 1, 4
• Other: Methadone, chloroquine, hydroxychloroquine 1

Important Clinical Caveat

While none of the four medications in question prolong QT interval, lithium (another mood stabilizer) has divergent reports regarding QT effects, with documented bradycardia, T wave changes, and AV-block 1. This demonstrates that within the same therapeutic class, individual agents can have vastly different cardiac safety profiles. However, the anticonvulsants specifically mentioned (carbamazepine, gabapentin, valproate) remain free of QT prolongation concerns based on current evidence 1.