Methadone (Methadone Hydrochloride) - Description and Clinical Pharmacology

CII

Rx only.

DESCRIPTION

Methadone Hydrochloride Tablets, USP are provided in tablet form for oral administration. Methadone Hydrochloride, USP 6-(dimethylamino)-4, 4-diphenyl-3-heptanone hydrochloride, is a white, essentially odorless, bitter-tasting powder. It is very soluble in water, soluble in isopropanol and in chloroform, and practically insoluble in ether and in glycerine. Methadone hydrochloride has a pKa of 8.25 in water at 20°C. Its molecular weight is 345.91 and it has the following structural formula.

Each tablet contains 5 mg (0.015 mmol) or 10 mg (0.029 mmol) methadone hydrochloride.

The tablets also contain Lactose Monohydrate NF, Magnesium Stearate NF, Microcrystalline Cellulose NF and Silicon Dioxide NF.

CLINICAL PHARMACOLOGY

Methadone hydrochloride is a synthetic narcotic analgesic with multiple actions quantitatively similar to those of morphine, the most prominent of which involve the central nervous system and organs composed of smooth muscle. The principal actions of therapeutic value are analgesia and sedation and detoxification or temporary maintenance in narcotic addiction. The methadone abstinence syndrome, although qualitatively similar to that of morphine, differs in that the onset is slower, the course is more prolonged, and the symptoms are less severe.

A parenteral dose of 8 to 10 mg of methadone is approximately equivalent in analgesic effect to 10 mg of morphine. With single-dose administration, the onset and duration of analgesic action of the 2 drugs are similar.

When administered orally, methadone is approximately one-half as potent as when given parenterally. Oral administration results in a delay of the onset, a lowering of the peak, and an increase in the duration of analgesic effect.