MEXILETINE HCL- mexiletine hydrochloride capsule
Watson Laboratories, Inc.
DESCRIPTION
Mexiletine hydrochloride is an orally active antiarrhythmic agent available as 150 mg, 200 mg and 250 mg capsules. 100 mg of mexiletine hydrochloride is equivalent to 83.31 mg of mexiletine base. It is a white to off-white crystalline powder with slightly bitter taste, freely soluble in water and in alcohol. Mexiletine hydrochloride has a pKa of 9.2.
Chemically, mexiletine hydrochloride is (�)-1-methyl-2-(2, 6-xylyloxy) ethylamine hydrochloride. Its molecular formula is C11 H17 NO�HCI and molecular weight is 215.72. Each capsule, for oral administration contains 150 mg, 200 mg, or 250 mg mexiletine hydrochloride. In addition, each capsule contains the following inactive ingredients: colloidal silicon dioxide, corn starch, D&C Red No. 28, D&C Yellow No. 10, FD&C Blue No. 1, FD&C Red No. 40, gelatin, magnesium stearate, pregelatinized starch, sodium lauryl sulfate, and titanium dioxide. Mexiletine hydrochloride capsules 150 mg also contain black iron oxide, red iron oxide, and yellow iron oxide. Mexiletine hydrochloride capsules 250 mg also contain FD&C Green No. 3.
CLINICAL PHARMACOLOGY
Mechanism of Action: Mexiletine hydrochloride is a local anesthetic, antiarrhythmic agent, structurally similar to lidocaine, but orally active. In animal studies, mexiletine has been shown to be effective in the suppression of induced ventricular arrhythmias, including those induced by glycoside toxicity and coronary artery ligation. 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.
Electrophysiology in Man: Mexiletine is a Class 1B antiarrhythmic compound with electrophysiologic properties in man similar to those of lidocaine, but dissimilar from quinidine, procainamide, and disopyramide.
