Mexiletine hydrochloride
Mexiletine hydrochloride (Mexitil)
Mexiletine hydrochloride
(mex- ILL-eh-teen)
Pregnancy Category: C Mexitil Novo-Mexiletine (Rx)

Classification: Antiarrhythmic, class IB

See Also: See also Antiarrhythmic Drugs .

Action/Kinetics: Similar to lidocaine but is effective PO. Inhibits the flow of sodium into the cell, thereby reducing the rate of rise of the action potential. The drug decreases the effective refractory period in Purkinje fibers. BP and pulse rate are not affected following use, but there may be a small decrease in CO and an increase in peripheral vascular resistance. Also has both local anesthetic and anticonvulsant effects. Onset: 30-120 min. Peak blood levels: 2-3 hr. Therapeutic plasma levels: 0.5-2 mcg/mL. Plasma t 1/2: 10-12 hr. Approximately 10% excreted unchanged in the urine; acidification of the urine enhances excretion, whereas alkalinization decreases excretion.

Uses: Documented life-threatening ventricular arrhythmias (such as ventricular tachycardia). Investigational: Prophylactically to decrease the incidence of ventricular tachycardia and other ventricular arrhythmias in the acute phase of MI. To reduce pain, dysesthesia, and paresthesia associated with diabetic neuropathy.

Contraindications: Cardiogenic shock, preexisting second- or third-degree AV block (if no pacemaker is present). Use with lesser arrhythmias. Lactation.

Special Concerns: There is the possibility of increased risk of death when used in clients with non-life-threatening cardiac arrhythmias. Use with caution in hypotension, severe CHF, or known seizure disorders. Dosage has not been established in children.

Side Effects: CV: Worsening of arrhythmias palpitations, chest pain, increased ventricular arrhythmias (PVCs), CHF, angina or angina-like pain, hypotension, bradycardia, syncope, AV block or conduction disturbances atrial arrhythmias, hypertension, cardiogenic shock hot flashes, edema. GI: High incidence of upper GI distress, N&V;, heartburn. Also, diarrhea or constipation, changes in appetite, dry mouth, abdominal cramps or pain, abdominal discomfort, salivary changes, dysphagia, altered taste, pharyngitis, changes in oral mucous membranes, upper GI bleeding, peptic ulcer, esophageal ulceration. CNS: High incidence of lightheadedness, dizziness, tremor, coordination difficulties, and nervousness. Also, changes in sleep habits, headache, fatigue, weakness, tinnitus, paresthesias, numbness, depression, confusion, difficulty with speech, short-term memory loss, hallucinations, malaise, psychosis, seizures loss of consciousness. Hematologic: Leukopenia, neutropenia, agranulocytosis, thrombocytopenia. GU: Decreased libido, impotence, urinary hesitancy or retention. Dermatologic: Rash, dry skin. Rarely, exfoliative dermatitis, and Stevens-Johnson syndrome. Miscellaneous: Blurred vision, visual disturbances, dyspnea, arthralgia, fever, diaphoresis, loss of hair, hiccoughs, laryngeal or pharyngeal changes, syndrome of SLE, myelofibrosis.

Laboratory Test Alterations: AST. Positive ANA. Abnormal LFTs.

Overdose Management: Symptoms: Nausea. CNS symptoms (dizziness, drowsiness, paresthesias, seizures) usually precede CV symptoms (hypotension, sinus bradycardia, intermittent left bundle branch block (LBBB), temporary asystole). Massive overdoses cause coma and respiratory arrest. Treatment: General supportive treatment. Give atropine to treat hypotension or bradycardia. Acidification of the urine may increase rate of excretion.

Drug Interactions: Aluminum hydroxide / Mexiletine absorption Atropine / Mexiletine absorption Caffeine / Drug clearance (50%) Cimetidine / or Plasma mexiletine levels Magnesium hydroxide / Mexiletine absorption Metoclopramide / Mexiletine absorption Narcotics / Mexiletine absorption Phenobarbital / Plasma mexiletine levels Phenytoin / Clearance plasma mexiletine levels Rifampin / Clearance plasma mexiletine levels Theophylline / Drug effect R/T serum levels Urinary acidifiers / Rate of mexiletine excretion Urinary alkalinizers / Rate of mexiletine excretion

How Supplied: Capsule: 150 mg, 200 mg, 250 mg

Dosage
?Capsules Antiarrhythmic.
Adults, individualized, initial: 200 mg q 8 hr if rapid control of arrhythmia not required; dosage adjustment may be made in 50- or 100-mg increments q 2-3 days, if required. Maintenance: 200-300 mg q 8 hr, depending on response and tolerance of client. If adequate response is not achieved with 300 mg or less q 8 hr, 400 mg q 8 hr may be tried although the incidence of CNS side effects increases. If the drug is effective at doses of 300 mg or less q 8 hr, the same total daily dose may be given in divided doses q 12 hr (e.g., 450 mg q 12 hr). Maximum total daily dose: 1,200 mg.
Rapid control of arrhythmias.
Initial loading dose: 400 mg followed by a 200-mg dose in 8 hr.
Diabetic neuropathy.
Initial: 150 mg/day for 3 days; then, 300 mg/day for 3 days. Maintenance: 10 mg/kg/day.