Antiarrhythmic comparison (oncology pharmacist focus)
Concise comparison table highlighting practical points for oncology practice — interactions, organ toxicity overlap with cancer therapies, monitoring, and dosing nuances.
| Drug | Class / Mechanism | Typical indications (relevant to oncology) | Renal dosing / adjustment | Hepatic metabolism / CYP interactions | QT risk (relative) | Key interactions with oncology drugs | Monitoring & practical notes for oncology pharmacists |
|---|---|---|---|---|---|---|---|
| Amiodarone | Class III (K⁺) — broad multichannel (Na⁺, K⁺, Ca²⁺) + noncompetitive β-block | AF/flutter, refractory ventricular tachycardia/fibrillation | No renal adjustment (primarily hepatic/biliary) | Metabolized by CYP3A4 & CYP2C8 → many interactions; active metabolite DEA | Moderate QT prolongation but low torsades risk compared to pure Class III drugs | ↑ Warfarin, ↑ digoxin, ↑ cyclosporine/tacrolimus; additive with QT-prolonging TKIs/ondansetron; CYP inhibitors increase amiodarone | Baseline CXR/PFTs, LFTs, TSH, ECG; long half-life → prolonged effects; avoid/monitor with bleomycin or chest RT (pulmonary risk) |
| Sotalol | Class III antiarrhythmic with nonselective β-blocking (K⁺ channel blocker) | AF conversion/maintenance, ventricular arrhythmias (selected cases) | Requires renal dose adjustment (renally cleared) and contraindicated with CrCl low (dose interval increased or avoid); careful in electrolyte abnormalities | Minimal hepatic metabolism (cleared unchanged renally) | High QT prolongation risk → torsades risk significant | Additive QT risk with TKIs, macrolides, fluoroquinolones, antiemetics; β-blocking may interact with hypotensive/AV-nodal agents used in oncology | Baseline QTc and renal function; monitor QTc after dose changes and with concurrent QT-prolonging chemo; adjust or avoid if CrCl <40 mL/min (specific thresholds depend on product) |
| Dofetilide | Pure Class III (K⁺ channel blocker) | Conversion/maintenance of AF; used when other agents unsuitable | Requires strict renal dosing and inpatient initiation/ECG monitoring; contraindicated if CrCl low | Minimal hepatic metabolism; renal elimination predominates | High QT prolongation risk (torsades) | Major interactions with strong CYP3A4 inhibitors and drugs that increase dofetilide levels (e.g., cimetidine, TMP-SMX); additive with oncologic QT drugs | Must be started with continuous ECG monitoring (in many jurisdictions), strict renal-dose table, frequent QT/RR checks; avoid with many common supportive meds that oncology patients receive |
| Lidocaine (IV) | Class IB — Na⁺ channel blocker (shortens action potential in ventricle) | Acute suppression of ventricular arrhythmias (VT, pulseless VT) — often emergency/ICU setting | No renal dose for bolus; active metabolites renally cleared — accumulation in renal failure possible with infusion | Hepatic metabolism (CYP1A2, CYP3A4) to active metabolites | Low QT effect (minimal) | Fewer QT interactions; cautious with other CNS depressants or drugs that reduce clearance (some CYP interactions with antifungals) | Useful for acute ventricular arrhythmias in ICU; monitor lidocaine levels if prolonged infusion or liver dysfunction; less overlap with oncology QT issues but watch neurotoxicity in patients with metabolic disturbances |
Quick practical comparisons (one-line takeaways)
- Amiodarone: Broad-spectrum and often preferred with structural heart disease; watch multi-system toxicities that overlap with oncologic treatments and many CYP interactions; effects persist after stopping.
- Sotalol: Effective but requires renal dosing and carries significant QT/torsades risk — avoid with many QT-prolonging chemo agents.
- Dofetilide: Powerful for AF but requires strict renal dosing and intensive monitoring; high drug-interaction potential with common antimicrobials and supportive meds.
- Lidocaine: Good for short-term treatment of ventricular arrhythmias in acute/ICU settings; minimal QT effect but metabolism dependent on liver; watch metabolites in renal failure.
Oncology-focused monitoring checklist (common to most agents)
- Baseline ECG (QTc), electrolytes (K⁺, Mg²⁺, Ca²⁺), renal function, hepatic function
- Review concurrent oncology drugs for QT risk (TKIs, antipsychotics, certain antiemetics) and CYP interactions (azole antifungals, macrolides, some TKIs)
- For agents with pulmonary or thyroid toxicity (amiodarone), coordinate with oncology for baseline imaging and thyroid labs if patients have prior pulmonary-toxic chemo or neck irradiation
- When switching or starting antiarrhythmics during chemotherapy cycles, re-check levels and ECG after starting agents that affect CYP enzymes or renal clearance
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