Mexiletine


Full Prescribing Info
Dosage/Direction for Use

Oral
Ventricular arrhythmias
Adult: As hydrochloride: 400 mg as loading dose followed after 2 hr by 200-250 mg 3-4 times daily. Maintenance: 600-900 mg daily in divided doses. Max dose: 1200 mg daily. Patient with MI: Higher loading dose e.g. 600 mg may be needed, especially if opioid analgesics were also given.
Renal impairment: Dose reduction may be needed.
Hepatic impairment:
Dose reduction may be needed.

Intravenous
Ventricular arrhythmias
Adult: As hydrochloride: 100-250 mg slow inj at 25 mg/min followed by 250 mg infusion over 1 hr, 250 mg for the next 2 hr and then 0.5 mg/min for maintenance, according to response. Transfer to oral dose of 200-250 mg 3-4 times daily when possible. Alternatively, 200 mg at 25 mg/min followed by 400 mg orally upon completion of inj, with subsequent oral dose of 200-250 mg 3-4 times daily.
Renal impairment: Dose reduction may be needed.
Hepatic impairment:
Dose reduction may be needed.
Administration
Should be taken with food.
Contraindications
Cardiogenic shock, 2nd- or 3rd-degree AV block (unless the patient has a pacemaker).
Special Precautions
Acute MI, sinus node dysfunction, conduction defects, bradycardia, hypotension, heart failure, hepatic impairment. Monitor ECG and BP. Correct electrolyte imbalance prior to and during therapy. Pregnancy.
Adverse Reactions
Nausea, vomiting, diarrhoea, constipation, oesophageal ulceration, confusion, lightheadedness, blurred vision, sleep disturbances, speech difficulties, exacerbated arrhythmias, hepatotoxicity, dizziness, tremor, nervousness, ataxia, sinus bradycardia, AV dissociation and atrial fibrillation.
Potentially Fatal: Cardiogenic shock, hepatic necrosis, Stevens-Johnson syndrome, heart block, sinus arrest.
Overdosage
With narrow therapeutic index; acute ingestion of twice the daily therapeutic dose may be life-threatening. Symptoms: Sedation, confusion, coma, seizures, respiratory arrest, sinus arrest, AV block, asystole, hypotension, dizziness, paraesthesia, tremor, ataxia, GI disturbance. Prolonged QRS and QT intervals (massive overdose). Management: Symptomatic and supportive.
Drug Interactions
Levels/effects may be reduced with CYP1A2 inducers (e.g. aminoglutethimide, carbamazepine, phenobarbital, rifampicin). Levels/effects may be increased with CYP1A2 inhibitors (e.g. ciprofloxacin, ketoconazole, norfloxacin, ofloxacin, rofecoxib), CYP2D6 inhibitors (e.g. chlorpromazine, delavirdine, fluoxetine, miconazole, paroxetine, pergolide, quinidine, quinine, ritonavir, ropinirole) and urinary alkalinisers (e.g. antacids, sodium bicarbonate, acetazolamide). May increase the levels/effects of CYP1A2 substrates e.g. aminophylline, fluvoxamine, mirtazapine, ropinirole, theophylline, trifluoperazine. Clearance reduced with fluvoxamine. Delayed absorption with opioid analgesics.
Potentially Fatal: Increased risk of arrhythmias with other antiarrhythmics or arrhythmogenic drugs. May precipitate lidocaine toxicity.
Food Interaction
Food may reduce rate but not the extent of oral absorption. Avoid dietary changes that alter urine pH since these may increase or decrease excretion of mexiletine.
Action
Mexiletine is a class Ib antiarrhythmic. It inhibits inward sodium current which decreases the rate of depolarisation of phase 0 of the action potential. It also increases effective refractory period (ERP) relative to the action potential duration (ERP/APD).
Absorption: Readily and almost completely absorbed from the GI tract (oral); may be delayed after MI.
Distribution: Distributed widely; crosses the placenta and enters breast milk. Protein-binding: 50-70%.
Metabolism: Hepatic via cytochrome P450 isoenzymes CYP1A2, CYP2D6, CYP3A4.
Excretion: Via urine (mainly as metabolites and 10% unchanged drug). Clearance increased in acid urine. Elimination half-life: 10 hr; may be prolonged in heart disease, hepatic impairment and severe renal impairment.
CIMS Class
ATC Classification
C01BB02 - mexiletine ; Belongs to class Ib antiarrhythmics.
Disclaimer: This information is independently developed by CIMS based on mexiletine from various references and is provided for your reference only. Therapeutic uses, prescribing information and product availability may vary between countries. Please refer to CIMS Product Monographs for specific and locally approved prescribing information. Although great effort has been made to ensure content accuracy, CIMS shall not be held responsible or liable for any claims or damages arising from the use or misuse of the information contained herein, its contents or omissions, or otherwise. Copyright © 2020 CIMS. All rights reserved. Powered by CIMSAsia.com
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