Amiodarone

證據等級: L5

預測適應症: 10 個

Amiodarone: From Ventricular Arrhythmias to Catecholaminergic Polymorphic Ventricular Tachycardia

One-Sentence Summary

Amiodarone is a well-established broad-spectrum antiarrhythmic agent used globally for life-threatening ventricular arrhythmias and atrial fibrillation, though it is not currently registered in Singapore. The TxGNN model predicts it may be effective for Catecholaminergic Polymorphic Ventricular Tachycardia (CPVT), a rare inherited cardiac channelopathy, with no registered clinical trials and 10 publications currently available to support this direction.

Quick Overview

Item	Content
Original Indication	Not registered in Singapore; globally indicated for ventricular fibrillation and life-threatening ventricular arrhythmias
Predicted New Indication	Catecholaminergic Polymorphic Ventricular Tachycardia (CPVT)
TxGNN Prediction Score	99.78%
Evidence Level	L4
Singapore Market Status	✗ Not Marketed
Number of Registrations	0
Recommended Decision	Hold

Why is This Prediction Reasonable?

Currently, detailed mechanism of action data is not available in this Evidence Pack. Based on known pharmacological information, Amiodarone is a Class III antiarrhythmic drug with uniquely broad multi-channel blocking properties. It inhibits delayed rectifier potassium channels (IKr/IKs) to prolong the cardiac action potential duration and effective refractory period, while simultaneously exerting sodium channel blockade (Class I), beta-adrenergic receptor antagonism (Class II), and L-type calcium channel inhibition (Class IV). This multi-class profile makes it a drug of last resort for arrhythmias refractory to conventional agents.

CPVT is caused by gain-of-function mutations in the RYR2 (ryanodine receptor 2) gene or loss-of-function mutations in CASQ2 (calsequestrin-2). Under catecholamine stimulation — exercise or emotional stress — these mutations cause pathological calcium leakage from the sarcoplasmic reticulum, producing delayed afterdepolarizations (DADs) that trigger polymorphic ventricular tachycardia and potentially fatal cardiac arrest. The mechanistic link between Amiodarone and CPVT is therefore indirect at best: although Amiodarone possesses calcium channel blocking activity, it does not directly modulate RyR2-mediated sarcoplasmic reticulum calcium release, which is the core dysfunction in CPVT.

By contrast, Flecainide has demonstrated direct RyR2 channel blockade independent of its sodium channel effects and has emerged as a more mechanistically targeted treatment for CPVT. Amiodarone's documented role in CPVT is largely limited to adjunctive rescue therapy during acute electrical storms, as reflected in the available case literature. The high TxGNN prediction score likely reflects knowledge graph associations derived from Amiodarone's broad antiarrhythmic utility rather than a specific CPVT mechanism.

Clinical Trial Evidence

Currently no related clinical trials registered for Amiodarone in catecholaminergic polymorphic ventricular tachycardia.

Literature Evidence

PMID	Year	Type	Journal	Key Findings
26513538	2015	Review	Expert Opinion on Pharmacotherapy	Reviews pharmacological management of ventricular arrhythmias; antiarrhythmic drugs including amiodarone remain important despite advances in non-pharmacologic therapy
35892906	2022	Cohort	Life (Basel)	Systematic review of CPVT clinical characteristics, genetic findings, and arrhythmic outcomes in Chinese patients; highlights phenotypic differences from Western cohorts
39076628	2022	Cohort	Reviews in Cardiovascular Medicine	Retrospective cohort examining CPVT clinical characteristics, genetic basis, healthcare utilisation, and costs in a Chinese city
22553997	2012	Case Series	Pacing and Clinical Electrophysiology	Flecainide (not amiodarone) suppresses ICD-induced arrhythmic storm in a 14-year-old with CPVT due to CASQ2 mutation; underscores RyR2-targeted therapy advantage
37852665	2023	Case Report	BMJ Case Reports	Pediatric out-of-hospital cardiac arrest; amiodarone used as part of multimodal resuscitation including 40 defibrillation shocks for refractory pulseless VT/VF
22218697	2012	Case Report	Anesthesia and Analgesia	Neonate with compound long QT mutation requiring multimodal therapy with amiodarone, esmolol, and lidocaine for refractory ventricular tachycardia
29668588	2018	Case Report	Medicine	Delayed CPVT diagnosis (RYR2 c.7580T>G mutation) in a 9-year-old child; illustrates diagnostic challenges and the consequences of delayed recognition
30116135	2018	Case Report	Turk Pediatri Arsivi	2-year-old presenting with sudden cardiac arrest caused by CPVT; genetic arrhythmia in the absence of structural heart disease
39735866	2024	Case Report	Frontiers in Cardiovascular Medicine	Successful resolution of refractory CPVT in a teenager via bilateral cardiac sympathetic denervation after failure of medical therapy
17125720	2006	Case Report	Revista Española de Cardiología	Arrhythmic storm triggered by ICD discharges in a CPVT patient; demonstrates complexity of device-therapy interactions in catecholamine-driven arrhythmias

Singapore Market Information

Amiodarone (DrugBank ID: DB01118) is not registered in Singapore. No Health Sciences Authority (HSA) authorisation records are available. The drug is therefore not legally marketed through standard channels in Singapore, and any clinical use would require special access pathways (e.g., Special Access Route or institutional compassionate use).

Safety Considerations

Please refer to the package insert for safety information. Formal warnings and contraindications specific to the Singapore/HSA label are not available, as the drug is not registered locally. Clinicians should consult established international references (e.g., FDA label, EMA SmPC) for Amiodarone's well-documented toxicity profile, which includes pulmonary toxicity, thyroid dysfunction, hepatotoxicity, and QT prolongation.

Conclusion and Next Steps

Decision: Hold

Rationale: Despite a high TxGNN prediction score (99.78%), the mechanistic link between Amiodarone and CPVT is weak — Amiodarone does not directly target the RyR2/CASQ2 calcium dysregulation that drives CPVT pathophysiology, no clinical trials have been conducted in this specific indication, and available literature supports only adjunctive or rescue use in acute arrhythmic emergencies rather than disease-specific CPVT therapy.

To proceed, the following is needed:

Mechanistic evidence: Pre-clinical or translational data demonstrating whether Amiodarone exerts any meaningful effect on RyR2-mediated calcium release in CPVT models
Safety data: Full review of the Amiodarone package insert (Singapore or international) for warnings, contraindications, and drug–drug interactions, particularly relevant given the drug's broad toxicity profile
Comparative positioning: Clarify Amiodarone's role relative to established CPVT therapies (nadolol, flecainide, cardiac sympathetic denervation) — current evidence suggests it offers no advantage as a primary agent
Registry or case series data: A prospective registry documenting Amiodarone outcomes specifically in CPVT patients who are refractory to beta-blockers and flecainide would be required before any formal repurposing evaluation can proceed
Regulatory pathway assessment: Given zero Singapore registrations, any development programme would need to account for HSA registration requirements from the outset
Disclaimer

This content is for research purposes only and does not constitute medical advice. Clinical validation is required before any clinical application.