Medical term:

Mexitil

mexiletine

(mex-il-e-teen) ,

Mexitil

(trade name)

Classification

Therapeutic: antiarrhythmics

Pregnancy Category: C

Indications

Prophylaxis/treatment of serious ventricular arrhythmias, including VT and PVCs.Management of chronic neuropathic pain.

Action

Decreases the duration of the action potential and effective refractory period in cardiac conduction tissue by altering transport of sodium across myocardial cell membranes.

Has little or no effect on heart rate.

Therapeutic effects

Control of ventricular arrhythmias.

Pharmacokinetics

Absorption: Well absorbed from the GI tract.

Distribution: Enters breast milk in concentrations similar to plasma.

Metabolism and Excretion: Mostly metabolized by the liver; 10% excreted unchanged by the kidneys.

Half-life: 10–12 hr.

Time/action profile (antiarrhythmic effects†)

ROUTE	ONSET	PEAK	DURATION
PO	30 min–2 hr	2–3 hr	8–12 hr

†Provided a loading dose has been given

Contraindications/Precautions

Contraindicated in: Hypersensitivity; Cardiogenic shock; 2nd- or 3rd-degree heart block (if a pacemaker has not been inserted); Lactation: Lactation.

Use Cautiously in: Sinus node or intraventricular conduction abnormalities; Hypotension; HF; Severe hepatic impairment (dosage reduction suggested); Obstetric / Pediatric: Safety not established.

Adverse Reactions/Side Effects

Central nervous system

dizziness (most frequent)
nervousness (most frequent)
confusion
fatigue
headache
sleep disorder

Ear, Eye, Nose, Throat

blurred vision
tinnitus

Respiratory

dyspnea

Cardiovascular

arrhythmias (life-threatening)
chest pain
edema
palpitations

Gastrointestinal

hepatic necrosis (life-threatening)
heartburn (most frequent)
nausea (most frequent)
vomiting (most frequent)

Dermatologic

rashes

Hematologic

blood dyscrasias

Neurologic

tremor (most frequent)
coordination difficulties
paresthesia

Interactions

Drug-Drug interaction

Opioid analgesics, atropine, and antacids may slow absorption.Metoclopramide may speed absorption.Phenytoin, rifampin, cigarette smoking, orphenobarbital may ↑ metabolism and ↓ effectiveness.Cimetidine may ↑levels.May ↑ levels and risk of toxicity from theophylline.Additive cardiac effects may occur with other antiarrhythmics.Drugs that drastically alter urine pH may alter blood levels (alkalinization ↑ reabsorption and blood levels; acidification ↑ excretion and ↓ levels).Foods that drastically alter urine pH may alter blood levels. Alkalinization ↑ reabsorption and ↑ levels. Acidification ↑ excretion and may ↓ effectiveness (see ).

Route/Dosage

Oral (Adults) 400-mg loading dose initially, then 200 mg 8 hr later, then 200–400 mg q 8 hr; dosage alterations of 50–100 mg may be made q 2–3 days. If controlled on ≤300 mg q 8 hr, can give same daily dose at 12-hr intervals (not to exceed 1200 mg/day). Some patients may require q 6 hr dosing.

Availability (generic available)

Capsules: 100 mg, 150 mg, 200 mg, 250 mg

Nursing implications

Nursing assessment

Monitor pulse, BP, and ECG periodically throughout therapy. Continuous Holter monitoring and chest x-ray examinations may be necessary to determine efficacy and aid in dosage adjustment.
Pain: Assess type, location, and severity of pain prior to and periodically throughout therapy.
Lab Test Considerations: May occasionally cause a positive ANA test result.
- May cause a transient increase in AST concentrations.
- May cause thrombocytopenia within a few days after initiation of therapy. Blood counts usually return to normal within 1 mo after discontinuation of therapy.

Potential Nursing Diagnoses

Decreased cardiac output (Indications)
Deficient knowledge, related to medication regimen (Patient/Family Teaching)

Implementation

When changing from other antiarrhythmic therapy, give the 1st dose of mexiletine 6–12 hr after the last dose of quinidine, 3–6 hr after last dose of procainamide, or 8–12 hr after last dose of tocainide. When changing from parenteral lidocaine, decrease lidocaine dose or discontinue lidocaine 1–2 hr after administration of mexiletine or administer lower initial doses of mexiletine.
- Transfer of patients with life-threatening arrhythmias from other antiarrhythmics to mexiletine should be managed in the hospital.
Oral: Administer with food or antacids to minimize GI irritation.

Patient/Family Teaching

Advise patient to take medication exactly as directed, at evenly spaced intervals, even if feeling well. Missed doses should be taken within 4 hr or omitted. Do not skip or double up on missed doses.
Teach patients to monitor pulse. Advise patient to contact health care professional if pulse rate is <50 bpm or becomes irregular.
May cause dizziness and light-headedness. Caution patient to avoid driving and other activities requiring alertness until response to medication is known.
Instruct patient to avoid changes in diet that may drastically acidify or alkalinize the urine (see for foods included).
Advise patient to notify health care professional of disease process and medication regimen prior to treatment or surgery.
Advise patient to notify health care professional if general tiredness, yellowing of the skin or eyes, fever, sore throat, or persistent side effects occur.
Patient should carry identification describing disease process and medication regimen at all times.

Evaluation/Desired Outcomes

Decrease in frequency or resolution of serious ventricular arrhythmias.
Decrease in severity of chronic neurogenic pain.

mexiletine

A class-IB anti-arrhythmic which shortens the repolarisation phase by blocking sodium channels. Mexiletine also has some currency in treating refractory pain, congenital myotonias and HIV-related neuropathy.

Adverse effects
Heartburn, dizziness, nausea, nervousness, trembling.

Mexitil

A brand name for MEXILETINE.

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