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Therapeutic drug monitoring: antiarrhythmic drugs
1Department of Clinical Pharmacology, St Vincent's Hospital, Darlinghurst, NSW, Australia.
Insights
Therapeutic drug monitoring (TDM) enhances the safe administration of certain antiarrhythmic agents, particularly Class I drugs and those like digoxin and perhexiline, by managing toxicity and ensuring compliance.
Area of Science:
- Pharmacology
- Cardiology
Background:
- Antiarrhythmic agents are classified using the Vaughan Williams system.
- Different classes have distinct mechanisms and safety profiles.
Purpose of the Study:
- To review the role of therapeutic drug monitoring (TDM) in the safe administration of various antiarrhythmic agents.
- To assess the necessity of TDM across different Vaughan Williams classes and other antiarrhythmics.
Main Methods:
- Review of antiarrhythmic drug classifications and their associated monitoring strategies.
- Analysis of the utility of TDM for specific drug classes and individual agents.
Main Results:
- Class I antiarrhythmics, while toxic, benefit significantly from TDM for safe administration.
- TDM is useful for amiodarone (Class III) and essential for digoxin and perhexiline.
- Class II (beta-blockers), Class IV (calcium channel blockers), sotalol, verapamil, and diltiazem generally do not require TDM.
Conclusions:
- TDM is crucial for optimizing the safety and efficacy of specific antiarrhythmic drugs.
- Monitoring strategies should be tailored to the drug class and individual agent's properties.
Abstract:
Antiarrhythmic agents are traditionally classified according to Vaughan Williams into four classes of action. Class I antiarrhythmic agents include most of the drugs traditionally thought of as antiarrhythmics, and have as a common action, blockade of the fast-inward sodium channel on myocardium. These agents have a very significant toxicity, and while they are being used less, therapeutic drug monitoring (TDM) does significantly increase the safety with which they can be administered. Class II agents are antisympathetic drugs, particularly the beta-adrenoceptor blockers. These are generally safe agents which do not normally require TDM. Class III antiarrhythmic agents include sotalol and amiodarone. TDM can be useful in the case of amiodarone to monitor compliance and toxicity but is generally of little value for sotalol. Class IV antiarrhythmic drugs are the calcium channel blockers verapamil and diltiazem. These are normally monitored by haemodynamic effects, rather than using TDM. Other agents which do not fall neatly into the Vaughan Williams classification include digoxin and perhexiline. TDM is very useful for monitoring the administration (and particularly the safety) of both of these agents.