Dextroamphetamine

Pronunciation

(deks troe am FET a meen)

U.S. Brand Names

Dexedrine®; Dextrostat®

Synonyms

Dextroamphetamine Sulfate

Generic Available

Yes

Canadian Brand Names

Dexedrine®

Use

Narcolepsy; attention-deficit/hyperactivity disorder (ADHD)

Use - Unlabeled/Investigational

Exogenous obesity; depression; abnormal behavioral syndrome in children (minimal brain dysfunction)

Restrictions

C-II

Pregnancy Risk Factor

Lactation

Enters breast milk/contraindicated

Contraindications

Hypersensitivity or idiosyncrasy to dextroamphetamine or other sympathomimetic amines. Patients with advanced arteriosclerosis, symptomatic cardiovascular disease, moderate to severe hypertension (stage II or III), hyperthyroidism, glaucoma, diabetes mellitus, agitated states, patients with a history of drug abuse, and during or within 14 days following MAO inhibitor therapy. Stimulant medications are contraindicated for use in children with attention-deficit/hyperactivity disorders and concomitant Tourette's syndrome or tics.

Warnings/Precautions

Use with caution in patients with bipolar disorder, cardiovascular disease, seizure disorders, insomnia, porphyria, mild hypertension (stage I), or history of substance abuse. May exacerbate symptoms of behavior and thought disorder in psychotic patients. Stimulants may unmask tics in individuals with coexisting Tourette's syndrome. Potential for drug dependency exists - avoid abrupt discontinuation in patients who have received for prolonged periods. Use in weight reduction programs only when alternative therapy has been ineffective. Products may contain tartrazine - use with caution in potentially sensitive individuals. Stimulant use in children has been associated with growth suppression.

Adverse Reactions

Frequency not defined.

Cardiovascular: Palpitations, tachycardia, hypertension, cardiomyopathy

Central nervous system: Overstimulation, euphoria, dyskinesia, dysphoria, exacerbation of motor and phonic tics, restlessness, insomnia, dizziness, headache, psychosis, Tourette's syndrome

Dermatologic: Rash, urticaria

Endocrine & metabolic: Changes in libido

Gastrointestinal: Diarrhea, constipation, anorexia, weight loss, xerostomia, unpleasant taste

Genitourinary: Impotence

Neuromuscular & skeletal: Tremor

Overdosage/Toxicology

Symptoms of overdose include restlessness, tremor, confusion, hallucinations, panic, dysrhythmias, nausea, and vomiting. There is no specific antidote for dextroamphetamine intoxication and treatment is primarily supportive. Hyperactivity and agitation usually respond to reduced sensory input; however, with extreme agitation, haloperidol (2-5 mg I.M. for adults) may be required.

Drug Interactions

Substrate of CYP2D6 (major)

Acidifiers: Very large doses of potassium acid phosphate or ammonium chloride may increase the renal elimination of amphetamines due to urinary acidification

Alkalinizers: Large doses of sodium bicarbonate or other alkalinizers may increase renal tubular reabsorption (decreased elimination) and diminish the effect of amphetamine; includes potassium or sodium citrate and acetate

Antipsychotics: Efficacy of amphetamines may be decreased by antipsychotics; in addition, amphetamines may induce an increase in psychotic symptoms in some patients

CYP2D6 inhibitors: May increase the levels/effects of dextroamphetamine. Example inhibitors include chlorpromazine, delavirdine, fluoxetine, miconazole, paroxetine, pergolide, quinidine, quinine, ritonavir, and ropinirole.

Furazolidone: Amphetamines may induce hypertensive episodes in patients receiving furazolidone

Guanethidine: Amphetamines inhibit the antihypertensive response to guanethidine; probably also may occur with guanadrel

MAO inhibitors: Severe hypertensive episodes have occurred with amphetamine when used in patients receiving MAO inhibitors; concurrent use or use within 14 days is contraindicated.

Norepinephrine: Amphetamines enhance the pressor response to norepinephrine

Sibutramine: Concurrent use of sibutramine and amphetamines may cause severe hypertension and tachycardia; use is contraindicated with SSRIs; amphetamines may increase the potential for serotonin syndrome when used concurrently with selective serotonin re-uptake inhibitors (including fluoxetine, fluvoxamine, paroxetine, and sertraline)

Tricyclic antidepressants: Concurrent of amphetamines with TCAs may result in hypertension and CNS stimulation; avoid this combination

Ethanol/Nutrition/Herb Interactions

Ethanol: Avoid ethanol (may increase CNS depression).

Food: Dextroamphetamine serum levels may be altered if taken with acidic food, juices, or vitamin C.

Herb/Nutraceutical: Avoid ephedra (may cause hypertension or arrhythmias).

Stability

Protect from light

Mechanism of Action

Blocks reuptake of dopamine and norepinephrine from the synapse, thus increases the amount of circulating dopamine and norepinephrine in cerebral cortex to reticular activating system; inhibits the action of monoamine oxidase and causes catecholamines to be released. Peripheral actions include elevated blood pressure, weak bronchodilator, and respiratory stimulant action.

Pharmacodynamics/Kinetics

Onset of action: 1-1.5 hours

Distribution: Vd: Adults: 3.5-4.6 L/kg; distributes into CNS; mean CSF concentrations are 80% of plasma; enters breast milk

Metabolism: Hepatic via CYP monooxygenase and glucuronidation

Half-life elimination: Adults: 10-13 hours

Time to peak, serum: Tmax: Immediate release: 3 hours; sustained release: 8 hours

Excretion: Urine (as unchanged drug and inactive metabolites)

Dosage

Oral:

Children:

Narcolepsy: 6-12 years: Initial: 5 mg/day; may increase at 5 mg increments in weekly intervals until side effects appear (maximum dose: 60 mg/day)

ADHD:

3-5 years: Initial: 2.5 mg/day given every morning; increase by 2.5 mg/day in weekly intervals until optimal response is obtained; usual range: 0.1-0.5 mg/kg/dose every morning with maximum of 40 mg/day

6 years: 5 mg once or twice daily; increase in increments of 5 mg/day at weekly intervals until optimal response is obtained; usual range: 0.1-0.5 mg/kg/dose every morning (5-20 mg/day) with maximum of 40 mg/day

Children >12 years and Adults:

Narcolepsy: Initial: 10 mg/day, may increase at 10 mg increments in weekly intervals until side effects appear; maximum: 60 mg/day

Exogenous obesity (unlabeled use): 5-30 mg/day in divided doses of 5-10 mg 30-60 minutes before meals

Administration

Do not crush sustained release drug product. Administer as single dose in morning or as divided doses with breakfast and lunch. Should be administered 30 minutes before meals and at least 6 hours before bedtime.

Monitoring Parameters

Growth in children and CNS activity in all

Dietary Considerations

Should be taken 30 minutes before meals and at least 6 hours before bedtime.

Patient Education

Take exactly as directed; do not increase dose or frequency without consulting prescriber. Drug may cause physical and/or psychological dependence. Take early in day to avoid sleep disturbance, 30 minutes before meals. Avoid alcohol, caffeine, or OTC medications that act as stimulants. You may experience restlessness, false sense of euphoria, or impaired judgment (use caution when driving or engaging in tasks requiring alertness until response to drug is known); dry mouth (frequent mouth care, sucking lozenges, or chewing gum may help); nausea or vomiting (small, frequent meals, frequent mouth care may help); constipation (increased exercise, fluids, fruit, or fiber may help); diarrhea (buttermilk, boiled milk, or yogurt may help); or altered libido (reversible). Patients with diabetes need to monitor serum glucose closely (may alter antidiabetic medication requirements). Report chest pain, palpitations, or irregular heartbeat; extreme fatigue or depression; CNS changes (aggressiveness, restlessness, euphoria, sleep disturbances); severe unremitting abdominal distress or cramping; blackened stool; changes in sexual activity; or blurred vision. Pregnancy/breast-feeding precautions: Inform prescriber if you are or intend to become pregnant. Do not breast-feed.

Cardiovascular Considerations

Amphetamines should be avoided in patients with known or suspected cardiovascular disease. They may precipitate marked increases in blood pressure, tachycardia, and tachyarrhythmias. These drugs are often used recreationally and inappropriately, particularly for appetite suppressant effects. Recreational use of amphetamines should be considered in otherwise healthy patients with new onset hypertension, tachycardia, or tachyarrhythmias.

Dental Health: Effects on Dental Treatment

Key adverse event(s) related to dental treatment: Xerostomia (normal salivary flow resumes upon discontinuation). Up to 10% of patients taking dextroamphetamines may present with hypertension. The use of local anesthetic without vasoconstrictor is recommended in these patients.

Dental Health: Vasoconstrictor/Local Anesthetic Precautions

Use vasoconstrictor with caution in patients taking dextroamphetamine. Amphetamines enhance the sympathomimetic response of epinephrine and norepinephrine leading to potential hypertension and cardiotoxicity.

Dosage Forms

Capsule, sustained release, as sulfate: 5 mg, 10 mg, 15 mg

Dexedrine® Spansule®: 5 mg, 10 mg, 15 mg

Tablet, as sulfate: 5 mg, 10 mg

Dexedrine®: 5 mg [contains tartrazine]

Dextrostat®: 5 mg, 10 mg [contains tartrazine]

References

Grinstead GF, "Ranitidine and High Concentrations of Phenylpropanolamine Cross React in the EMIT Monoclonal Amphetamine/Methamphetamine Assay," Clin Chem , 1989, 35(9):1998-9.

Mattson RH and Calverley JR, "Dextroamphetamine-Sulfate-Induced Dyskinesias," JAMA , 1968, 204(5):400-2.

Richards CF, Clark RF, Holbrook T, et al, "The Effect of Cocaine and Amphetamines on Vital Signs in Trauma Patients," J Emerg Med , 1995, 13(1):59-63.

Segar DL, "Substances of Abuse: Topics," Emerg Med , 1985, 7:18-30.

Warden C and Winger J, "Choreoathetoid Reaction Associated With a Methylphenidate Ingestion in a Toddler," Clin Toxicol , 1995, 33(5):522.

International Brand Names

Dexedrine® (CA)

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