Drug information of Mexiletine

Mexiletine

Drug group:

Mexiletine affects the way that your heart beats. Mexiletine is used to treat seriously irregular heartbeats.

Mechanism of effect

Mexiletine, like lidocaine, inhibits the inward sodium current, thus reducing the rate of rise of the action potential, Phase 0. Mexiletine decreased the effective refractory period (ERP) in Purkinje fibers. The decrease in ERP was of lesser magnitude than the decrease in action potential duration (APD), with a resulting increase in the ERP/APD ratio.

Pharmacodynamic

Mexiletine hydrochloride is a local anesthetic, antiarrhythmic agent, structurally similar to lidocaine, but orally active.

Pharmacokinetics

Mexiletine is well absorbed (~90%) from the gastrointestinal tract. Unlike lidocaine, its first-pass metabolism is low. Peak blood levels are reached in two to three hours. In normal subjects, the plasma elimination half-life of Mexiletine is approximately 10 to 12 hours. It is 50 to 60% bound to plasma protein. Mexiletine is mainly metabolized in the liver, Approximately 10% is excreted unchanged by the kidney. The urinary excretion of N-methylmexiletine in man is less than 0.5%.

Drug indications

Ventricular Arrhythmia

Dosage

Usual Adult Dose for Ventricular Tachycardia
Initial dose: 200 mg orally every 8 hours when rapid control of arrhythmia is not essential.
A minimum of 2-3 days between dose adjustments is recommended.
Dose may be adjusted in 50 or 100 mg increments up or down.
Usual Pediatric Dose for Arrhythmias
1.4 to 5 mg/kg/dose given every 8 hours. Begin with lower initial dosages and titrate to desired effects and serum concentrations.

Alerts

1- the use of Mexiletine as well as other antiarrhythmic agents should be reserved for patients with life-threatening ventricular arrhythmia.
2- In postmarketing experience abnormal liver function tests have been reported, some in the first few weeks of therapy with Mexiletine hydrochloride.
3- Mexiletine should be used with caution in patients with hypotension and severe congestive heart failure because of the potential for aggravating these conditions.
4- If significant hematologic changes are observed, the patient should be carefully evaluated, and, if warranted, Mexiletine should be discontinued. Blood counts usually return to normal within a month of discontinuation
5- Mexiletine should be used with caution in patients with known seizure disorder.

Points of recommendation

1-As the severity of CNS side effects increases with total daily dose, the dose should not exceed 1200 mg/day.
2- Patients with severe liver disease may require lower doses and must be monitored closely.
3- Take with food to reduce irritation.

Pregnancy level

C

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