METHADONE HYDROCHLORIDE

METHADONE HYDROCHLORIDE
(meth'a-done)
Dolophine, Methadose
Classifications: narcotic (opiate) agonist; analgesic;
Therapeutic:narcotic (opiate) analgesic
Prototype: Morphine
Pregnancy Category: C
Controlled Substance: Schedule II

Availability

5 mg, 10 mg, 40 mg tablets; 1 mg/mL, 2 mg/mL, 10 mg/mL oral solution; 10 mg/mL injection

Action

Synthetic narcotic similar to morphine but is orally effective and has longer duration of action. It is a CNS depressant that causes sedation and respiratory depression. Highly addictive, with abuse potential that matches morphine; abstinence syndrome develops more slowly, and withdrawal symptoms are less intense but more prolonged.

Therapeutic Effect

Relieves severe pain and manages withdrawal therapy from narcotics, especially heroin.

Uses

To relieve severe pain; for detoxification and temporary maintenance treatment in hospital and in federally controlled maintenance programs for ambulatory patients with narcotic abstinence syndrome.

Contraindications

Severe pulmonary disease; COPD; obstetric analgesia; pregnancy (category C).

Cautious Use

History of QT prolongation; liver, kidney, or cardiac dysfunction.

Route & Dosage

Pain
Adult: PO/SC/IM 2.5–10 mg q3–4h prn IV 2.5-10 mg q8–12h prn (opiate na?ve patient)
Child: PO/IV/SC/IM 0.1–0.2 mg/kg q4h times 2–3 doses, then q6–12h prn (max: 5–10 mg/dose)

Detoxification Treatment
Adult: PO/SC/IM 15–40 mg once/d, usually maintained at 20–120 mg/d

Renal Impairment
Cl_cr <10 mL/min: use 50–75% of dose

Administration

Oral

Give for analgesic effect in the smallest effective dose to minimize the possible tolerance and physical and psychic dependence.
Dilute dispersible tablets in 120 mL of water or fruit juice and allow at least 1 min for dispersion.

Subcutaneous/Intramuscular

Note: IM route is preferred over SC when repeated parenteral administration is required (SC injections may cause local irritation and induration). Rotate injection sites.

Intravenous

PREPARE: Direct/IV Infusion: May be given undiluted or diluted with 1–5 mL of NS.

ADMINISTER: Direct/IV Infusion: Give over 5 or more minutes.

INCOMPATIBILITIES Y-site: Phenytoin.

Store at 15°–30° C (59°–86° F) in tight, light-resistant containers.

Adverse Effects (≥1%)

CNS: Drowsiness, light-headedness, dizziness, hallucinations. GI: Nausea, vomiting, dry mouth, constipation. Body as a Whole: Transient fall in BP, bone and muscle pain. Urogenital: Impotence. Respiratory: Respiratory depression.

Interactions

Drug: Alcohol and other cns depressants, cimetidine add to sedation and CNS depression; amphetamines may potentiate CNS stimulation; with mao inhibitors, selegiline, furazolidone causes excessive and prolonged CNS depression, convulsions, cardiovascular collapse. Food: Grapefruit juice may increase serum levels and adverse effects. Herbal: St. John's wort decreases plasma levels.

Pharmacokinetics

Absorption: Well absorbed from GI tract, variable IM absorption. Onset: 30–60 min PO; 10–20 min IM/SC. Peak: 1–2 h. Duration: 6–8 h PO, IM, SC; may last 22–48 h with chronic dosing. Distribution: Crosses placenta; distributed into breast milk. Metabolism: In liver (CYP3A4). Elimination: In urine. Half-Life: 15–25 h.

Nursing Implications

Assessment & Drug Effects

Evaluate patient's continued need for methadone for pain. Adjustment of dosage and lengthening of between-dose intervals may be possible.
Monitor respiratory status. Principal danger of overdosage, as with morphine, is extreme respiratory depression.
Be aware that because of the cumulative effects of methadone, abstinence symptoms may not appear for 36–72 h after last dose and may last 10–14 d. Symptoms are usually of mild intensity (e.g., anorexia, insomnia, anxiety, abdominal discomfort, weakness, headache, sweating, hot and cold flashes).
Observe closely for recurrence of respiratory depression during use of narcotic antagonists such as naloxone, naltrexone, and levallorphan to terminate methadone intoxication. Since antagonist action is shorter (1–3 h) than that of methadone (36–48 h or more), repeated doses for 8–24 h may be required.

Patient & Family Education

Be aware that orthostatic hypotension, sweating, constipation, drowsiness, GI symptoms, and other transient adverse effects of therapeutic doses appear to be more prominent in ambulatory patients. Most adverse effects disappear over a period of several weeks.
Make position changes slowly, particularly from lying down to upright position; sit or lie down if you feel dizzy or faint.
Do not drive or engage in potentially hazardous activities until response to drug is known.

Common adverse effects in italic, life-threatening effects underlined; generic names in bold; classifications in SMALL CAPS; Canadian drug name; Prototype drug

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