dextroamphetamine sulfate
Dexedrine, Dexedrine Spansules, Dextrostat

Available forms
Available by prescription only
Capsules (sustained-release): 5 mg, 10 mg, 15 mg
Tablets: 5 mg, 10 mg

Indications and dosages
 Narcolepsy. Adults: 5 to 60 mg P.O. daily in divided doses. Long-acting dosage forms allow once-daily dosing.
Children older than age 12: 10 mg P.O. daily, increased in 10-mg increments weekly, as indicated.
Children ages 6 to 12: 5 mg P.O. daily, increased in 5-mg increments weekly, as indicated. Maximum dosage is 60 mg/day.
 Short-term adjunct in exogenous obesity ◇. Adults: 5 to 30 mg P.O. daily 30 to 60 minutes before meals in divided doses of 5 to 10 mg. Or, give one 10- or 15-mg sustained-release capsule daily as a single dose in the morning.
 Attention deficit hyperactivity disorder (ADHD). Children age 6 and older: 5 mg P.O. once daily or b.i.d., increased by 5-mg increments weekly, p.r.n. Total daily dose should rarely exceed 40 mg. Usual dosage is 0.1 to 0.5 mg/ kg/dose q a.m.
Children ages 3 to 5: 2.5 mg P.O. daily, increased by 2.5-mg increments weekly, as needed; not recommended for children younger than age 3. Usual dosage is 0.1 to 0.5 mg/kg/dose q a.m.

Pharmacodynamics
CNS stimulant action: Amphetamines are sympathomimetic amines with CNS stimulant activity. In hyperactive children, they have a paradoxical calming effect.
Anorexigenic action: Anorexigenic effects are thought to occur in the hypothalamus, where decreased smell and taste acuity decreases appetite. They may be tried for short-term control of refractory obesity, with caloric restriction and behavior modification.
 The cerebral cortex and reticular activating system appear to be the primary sites of activity; amphetamines release nerve terminal stores of norepinephrine, promoting nerve impulse transmission. At high dosages, effects are mediated by dopamine.
 Amphetamines are used to treat narcolepsy and as adjuncts to psychosocial measures in ADHD in children. Their precise mechanism of action in these conditions is unknown.

Pharmacokinetics
Absorption: Rapidly absorbed from the GI tract within 3 hours.
Distribution: Distributed widely throughout the body.
Metabolism: Metabolized by the liver by aromatic hydroxylation, N-dealkylation, and deamination.
Excretion: Excreted in urine.

Contraindications and precautions
Contraindicated in patients hypersensitive to sympathomimetic amines, patients with idiosyncratic reactions to them, patients who have taken an MAO inhibitor within 14 days, and patients with hyperthyroidism, moderate to severe hypertension, symptomatic CV disease, glaucoma, advanced arteriosclerosis, or history of drug abuse. Use cautiously in patients with motor and phonic tics, Tourette syndrome, and agitated states.

Interactions
Drug-drug. Acetazolamide, alkalizing agents, antacids, sodium bicarbonate: Enhances renal reabsorption of dextroamphetamine. Monitor patient for enhanced amphetamine effects.
Acidifying agents, ammonium chloride, ascorbic acid: Enhances dextroamphetamine excretion and shortens duration of action. Monitor patient for decreased amphetamine effects.
Adrenergic blockers: Inhibits these drugs. Avoid use together.
Antihypertensives: May antagonize antihypertensive effects. Avoid use together.
Barbiturates: Antagonizes dextroamphetamine by CNS depression. Avoid use together.
Chlorpromazine: Inhibits the central stimulant effects of amphetamines. Can be used to treat amphetamine poisoning.
CNS stimulants, haloperidol, phenothiazines, theophylline, tricyclic antidepressants: Increases CNS effects. Avoid use together.
Insulin, oral antidiabetics: May alter need for these drugs. Monitor blood glucose levels.
Lithium carbonate: May inhibit antiobesity and stimulating effects of amphetamines. Monitor patient closely.
MAO inhibitors: May cause hypertensive crisis. Don’t use within 14 days of MAO inhibitor therapy.
Meperidine: Amphetamines potentiate analgesic effect. Use together cautiously.
Methenamine therapy: Increases urinary excretion of amphetamines and reduces efficacy. Monitor patient closely.
Norepinephrine: Amphetamines enhance the adrenergic effect. Monitor patient closely.
Phenobarbital, phenytoin: May produce a synergistic anticonvulsant action. Monitor patient closely.
Tricyclic antidepressants: May decrease effects of amphetamines. Monitor patient for decreased effects.
Drug-food. Caffeine: May increase amphetamine and related amine effects. Discourage use together.

Adverse reactions
CNS: restlessness, tremor, insomnia, dizziness, headache, chills, overstimulation, dysphoria, euphoria.
CV: tachycardia, palpitations, hypertension, arrhythmias.
GI: dry mouth, unpleasant taste, diarrhea, constipation, anorexia, weight loss, other GI disturbances.
GU: impotence.
Skin: urticaria.
Other: altered libido.

Effects on lab test results
• May increase plasma corticosteroid levels.

Overdose and treatment
Individual responses vary widely. Toxic symptoms may occur at 15 and 30 mg and can cause severe reactions; however, doses of 400 mg or more haven’t always proved fatal. Symptoms of overdose include restlessness, tremor, hyperreflexia, tachypnea, confusion, aggressiveness, hallucinations, and panic; fatigue and depression usually follow excitement stage. Other symptoms may include arrhythmias, shock, alterations in blood pressure, nausea, vomiting, diarrhea, and abdominal cramps; death is usually preceded by seizures and coma.
 Treat overdose symptomatically and supportively. If ingestion was recent (within 4 hours), use gastric lavage or emesis and then administer charcoal 1g/kg and a saline cathartic and sedate with a barbiturate; monitor vital signs and fluid and electrolyte balance. Urinary acidification may enhance excretion. Saline catharsis (magnesium citrate) may hasten GI evacuation of unabsorbed sustained-release drug.

Special considerations
• Drug may elevate plasma corticosteroid levels and may interfere with urinary steroid determinations.
• Give dextroamphetamine 30 to 60 minutes before meals when using as an anorexigenic agent. To minimize insomnia, avoid giving drug within 6 hours of bedtime.
• For narcolepsy, patient should take first dose on awakening.
• When tolerance to anorexigenic effect develops, dosage should be discontinued, not increased.
• Monitor blood and urine glucose levels. Drug may alter daily insulin requirement in patients with diabetes.
Breast-feeding patients
• Safety hasn’t been established. Breast-feeding isn’t recommended.
Pediatric patients
• Drug isn’t recommended for treatment of obesity in children younger than age 12 or for treatment of attention deficit disorder in children younger than age 3.
Geriatric patients
• Use lower doses. Avoid in elderly patients with CV, CNS, or GI disturbances.

Patient education
• Teach parents about drug-free periods for children with ADHD, especially during periods of reduced stress.
• Warn patient to avoid hazardous activities that require alertness until CNS response is determined.
• Instruct patient to take drug early in the day to minimize insomnia.
• Tell patient not to crush sustained-release forms or to increase dosage.

Reactions may be common, uncommon, life-threatening, or COMMON AND LIFE THREATENING.
◆ Canada only
◇ Unlabeled clinical use