METHAMPHETAMINE HYDROCHLORIDE

METHAMPHETAMINE HYDROCHLORIDE
(meth-am-fet'a-meen)
Desoxyephedrine, Desoxyn
Classifications: cerebral stimulant; anorexiant; amphetamine;
Therapeutic: cerebral stimulant; anorexiant

Prototype: Amphetamine sulfate
Pregnancy Category: C
Controlled Substance: Schedule II

Availability

5 mg tablets; 5 mg, 10 mg, 15 mg long-acting tablets

Action

Sympathomimetic amine chemically related to amphetamine. CNS stimulant actions approximately equal to those of amphetamine, but accompanied by less peripheral activity. However, larger doses produce increased cardiac output, possibly reflex slowing of heart rate, and sustained increase in BP, chiefly by cardiac stimulation.

Therapeutic Effect

CNS stimulant actions approximately equal to those of amphetamine, but accompanied by less peripheral activity.

Uses

Short-term adjunct in management of exogenous obesity, as adjunctive therapy in attention deficit disorder (ADD), narcolepsy, epilepsy, and postencephalitic parkinsonism, and in treatment of certain depressive reactions, especially when characterized by apathy and psychomotor retardation.

Contraindications

During pregnancy, especially first trimester (category C), lactation; as anorexiant in children <12 y; patients receiving MAO INIBITORS; arteriosclerotic parkinsonism.

Cautious Use

Mild hypertension; psychopathic personalities; hyperexcitability states; history of suicide attempts; older adult or debilitated patients.

Route & Dosage

Attention Deficit Disorder
Child (≥6 y): PO 2.5–5 mg 1–2 times/d, may increase by 5 mg at weekly intervals up to 20–25 mg/d

Obesity
Adult: PO 2.5–5 mg 1–3 times/d 30 min before meals or 5–15 mg of long-acting form once/d

Administration

Oral
  • Give early in the day to avoid insomnia, if possible.
  • Ensure that long-acting tablets are not chewed or crushed; these need to be swallowed whole.
  • Give 30 min before each meal when used for treatment of obesity. If insomnia results, advise patient to inform physician.
  • Preserve in tight, light-resistant containers.

Adverse Effects (≥1%)

CNS: Restlessness, tremor, hyperreflexia, insomnia, headache, nervousness, anxiety, dizziness, euphoria or dysphoria. CV: Palpitation, arrhythmias, hypertension, hypotension, circulatory collapse. GI: Dry mouth, unpleasant taste, nausea, vomiting, diarrhea, constipation. Special Senses: Increased intraocular pressure.

Interactions

Drug: Acetazolamide, sodium bicarbonate decreases methamphetamine elimination; ammonium chloride, ascorbic acid increases methamphetamine elimination; effects of both methamphetamine and barbiturates may be antagonized; furazolidone may increase BP effects of amphetamines—interaction may persist for several weeks after discontinuing furazolidone; antagonizes antihypertensive effects of guanethidine; mao inhibitors, selegiline can cause hypertensive crisis (fatalities reported)—do not administer amphetamines during or within 14 d of administration of these drugs; phenothiazines may inhibit mood elevating effects of amphetamines; tricyclic antidepressants enhance methamphetamine effects because they increase norepinephrine release; beta-adrenergic agonists increase adverse cardiovascular effects of amphetamines.

Pharmacokinetics

Absorption: Readily absorbed from the GI tract. Duration: 6–12 h. Distribution: All tissues especially the CNS; excreted in breast milk. Metabolism: In liver. Elimination: Renal elimination.

Nursing Implications

Assessment & Drug Effects

  • Monitor weight throughout period of therapy.
  • Be alert for paradoxic increase in depression or agitation in depressed patients. Report immediately; drug should be withdrawn.
  • Do not exceed duration of a few weeks for treatment of obesity.

Patient & Family Education

  • Be alert for development of tolerance; happens readily, and prolonged use may lead to drug dependence. Abuse potential is high. Methamphetamine is commonly known as "speed" or "crystal" among drug abusers.
  • Withdrawal after prolonged use is frequently followed by lethargy that may persist for several weeks.
  • Weigh every other day under standard conditions and maintain a record of weight loss.

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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