Title: Is there an interaction between amiodarone and mexiletine? Enq. No: 172

Transcription

1 Demonstration Site Title: Is there an interaction between amiodarone and mexiletine? Enq. No: 172 Due By: 17/05/ :15:23 Comments: Answer needed within the next 30 minutes. Date completed: 17/05/ :15:16 Completed by: DD Reply Authorised by: Enquirer Details J B Cardiology Pharmacist Coronary Care Unit Tel:x1234 Base Hospital Contact For This Enquiry:x1234 Patient Details Name: P J Age: 42 Sex: Male Patient Notes: Consultant: Dr K S Location: Coronary Care Unit Medical Details: Paroxysmal SVT (Chronic) Ventricular Tachycardia (Present Complaint) Patient Medication Amiodarone Dose: 200mg od Prescribed For: Notes: Dose: Prescribed For: Notes: Want to prescribe as a 24 hour infusion. Date Taken: 17/05/ :45:23 Taken By: SS Question Is there an interaction between amiodarone and mexiletine? Comments: The cardiology pharmacist (enquirer) only wants the interaction investigated. She will be closely monitoring the patient and will come down to MI later with any other queries. End of Question

2 Answer Tosardes de Pointes has been reported in a patient that was taking amiodarone and mexiletine. But this was an isolated case report and there are cases where giving both together has been shown to be beneficial. One resource suggested using lower initial starting doses of anti-antiarrhythmics added to amiodarone. You may wish to consider this approach. You confirm with the pharmacist that the patient is under 24 hour ECG monitoring. You therefore recommend that amiodarone and mexiletine can be used together and that the medical and nursing staff should watch out for any rhythm abnormalities especially QT prolongation and Torsades de Pointes. End of Answer Statistics Enquirer Status: Hospital Pharmacy Staff Origin: Base Organisation Local Origin: none specified Enquiry Route: Telephone TimeTaken: 30 minutes Reply Routes: Telephone Research References: Source: BNF (British National Formulary) Online * Source: <Other E-Source> Source: Stockley's Drug Interactions* Source: Martindale: The Complete Drug Reference Source: AHFS Drug Information Source: MedScape Drug Interactions Checker Enquiry Categories: Patient-Centred Enquiry,Interactions, ResponseTime: Under 1 Hour Enquiry Level: Level 2 On Time: True Keywords Keywords: AMIODARONE,MEXILETINE,TACHYCARDIA,ARRHYTHMIA-VENTRICULAR, Research Summary Source: BNF (British National Formulary) Online *

3 Author: Date Added: 17/05/ :48:13 Anti-arrhythmics and Anti-arrhythmics Increased myocardial depression when anti-arrhythmics given with other anti-arrhythmics. Source: <Other E-Source> Edition: Author: Publisher: Date Added: 17/05/ :52:16 Electronic Medicines Compendium URL: Online edition current as at May Amiodarone - Cordarone No interactions with mexiletine or other class Ib agents mentioned. Not listed. Source: Stockley's Drug Interactions* Edition: Online Author: Stockley, I Date Added: 17/05/ :57:27 Amiodarone and Amiodarone does not affect the clearance of mexiletine. In 10 patients the clearance of mexiletine was found to be unchanged when assessed after 1, 3 and 5 months of the concurrent use of amiodarone. In addition, the clearance of mexiletine did not differ between these patients and 155 other patients not taking amiodarone. Torsades de Pointes has been described in a patient taking amiodarone and mexiletine (a class Ib antiarrhythmic). The manufacturers of mexiletine say that this seems to be an isolated case. The two drugs have been used together successfully. Class Ib antiarrhythmics are usually associated with shortening of the QT interval, and could therefore be expected to

4 reduce QT prolongation and the risk of Torsades de Pointes seen with amiodarone. This has been seen with quinidine. Source: Martindale: The Complete Drug Reference Author: Sweetman, SC et al (Eds) Date Added: 17/05/ :02:39 There may be an increased risk of arrhythmias if mexiletine is used with other antiarrhythmics or with arrhythmogenic drugs Source: AHFS Drug Information Edition: Current edition Author: McEvoy GK (ed) Publisher: American Society of Hospital Pharmacists Date Added: 17/05/ :05:01 Amiodarone Torsades de Pointes has been reported rarely when amiodarone was administered concomitantly with mexiletine. Pending further accumulation of data, amiodarone should be used with caution when administered concomitantly with other antiarrhythmic agents, especially class Ia. If combination therapy with the other antiarrhythmic agent(s) is continued, patients should be monitored with particular care for possible adverse effects, especially conduction disturbances and exacerbation of tachyarrhythmias. In patients already receiving amiodarone, the initial dosage of other antiarrhythmic agents should be reduced to approximately 50% of their usual recommended initial dosages. Improved control of ventricular ectopy may occur in patients receiving other antiarrhythmic agents. Source: MedScape Drug Interactions Checker Author: Publisher: WebMD URL: Date Added: 17/05/ :10:17

5 Amiodarone + mexiletine 1 Interaction found: amiodarone will increase the level or effect of mexiletine by affecting hepatic enzyme CYP2D6 metabolism. Significant - Monitor Closely. End of Research Summary