Methamphetamine: Drug information

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(For additional information see "Methamphetamine: Patient drug information")

U.S. BRAND NAMES — Desoxyn®

PHARMACOLOGIC CATEGORY Anorexiant Stimulant Sympathomimetic

DOSING: ADULTS ADHD: Oral: 5 mg 1-2 times/day, may increase by 5 mg increments weekly until optimum response is achieved, usually 20-25 mg/day

Exogenous obesity: Oral: 5 mg, 30 minutes before each meal; treatment duration should not exceed a few weeks

DOSING: PEDIATRIC ADHD: Oral: Children 6 years: Refer to adult dosing.

Exogenous obesity: Oral: Children 12 years: Refer to adult dosing.

DOSING: ELDERLY — Refer to adult dosing.

DOSAGE FORMS — Excipient information presented when available (limited, particularly for generics); consult specific product labeling.

Tablet, as hydrochloride: 5 mg

DOSAGE FORMS: CONCISE Tablet: 5 mg   Desoxyn®: 5 mg

GENERIC EQUIVALENT AVAILABLE — Yes

USE — Treatment of attention-deficit/hyperactivity disorder (ADHD); exogenous obesity (short-term adjunct)

USE - UNLABELED / INVESTIGATIONAL — Narcolepsy

ADVERSE REACTIONS SIGNIFICANT — Frequency not defined.

Cardiovascular: Hypertension, tachycardia, palpitation

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

Dermatologic: Rash, urticaria

Endocrine & metabolic: Change in libido

Gastrointestinal: Diarrhea, nausea, vomiting, stomach cramps, constipation, anorexia, weight loss, xerostomia, unpleasant taste

Genitourinary: Impotence

Neuromuscular & skeletal: Tremor

Miscellaneous: Suppression of growth in children, tolerance and withdrawal with prolonged use

CONTRAINDICATIONS — Hypersensitivity to methamphetamine, any component of the formulation, or idiosyncrasy to amphetamines or other sympathomimetic amines; patients with advanced arteriosclerosis, symptomatic cardiovascular disease, moderate-to-severe hypertension, hyperthyroidism, glaucoma, agitated states; patients with a history of drug abuse; use 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 Box warnings:

• Drug abuse: See "Disease-related concerns" below.

• Weight reduction: Appropriate use: See "Disease-related concerns" below.

Concerns related to adverse effects:

• Cardiovascular events: Use has been associated with serious cardiovascular events including sudden death in patients with pre-existing structural cardiac abnormalities or other serious heart problems (sudden death in children and adolescents; sudden death, stroke and MI in adults). These products should be avoided in the patients with known serious structural cardiac abnormalities, cardiomyopathy, serious heart rhythm abnormalities, or other serious cardiac problems that could increase the risk of sudden death that these conditions alone carry. Patients should be carefully evaluated for cardiac disease prior to initiation of therapy.

• CNS effects: Amphetamines may impair the ability to engage in potentially hazardous activities.

• Visual disturbance: Difficulty in accommodation and blurred vision has been reported with the use of stimulants.

Disease-related concerns:

• Diabetes: Use with caution in patients with diabetes mellitus; antidiabetic agent requirements may be altered with anorexigens and concomitant dietary restrictions.

• Drug abuse: [U.S. Boxed Warning]: Potential for drug dependency exists; prolonged use may lead to drug dependency. Use is contraindicated in patients with history of ethanol or drug abuse. Prescriptions should be written for the smallest quantity consistent with good patient care to minimize possibility of overdose.

• Hypertension: Use with caution in patients with hypertension and other cardiovascular conditions that might be exacerbated by increases in blood pressure or heart rate. Use is contraindicated in patients with moderate to severe hypertension.

• Psychiatric disorders: Use with caution in patients with pre-existing psychosis or bipolar disorder (may induce mixed/manic episode). May exacerbate symptoms of behavior and thought disorder in psychotic patients; new onset psychosis or mania may occur with stimulant use; observe for symptoms of aggression and/or hostility.

• Seizure disorder: Use with caution in patients with a history of seizure disorder; may lower seizure threshold leading to new onset or breakthrough seizure activity.

• Tourette's syndrome: Use with caution in patients with Tourette's syndrome; stimulants may unmask tics.

• Weight reduction: Appropriate use: [U.S. Boxed Warning]: Use in weight reduction programs only when alternative therapy has been ineffective.

Special populations:

• Pediatrics: Safety and efficacy have not been established in children <12 years of age for obesity. Use of stimulants has been associated with suppression of growth; monitor growth rate during treatment.

Other warnings/precautions:

• Discontinuation of therapy: Abrupt discontinuation following high doses or for prolonged periods may result in symptoms for withdrawal. Discontinue if satisfactory weight loss has not occurred within the first 4 weeks of treatment, or if tolerance develops.

RESTRICTIONS — C-II

An FDA-approved medication guide must be distributed when dispensing an outpatient prescription (new or refill) where this medication is to be used without direct supervision of a healthcare provider. Medication guides are available at http://www.fda.gov/cder/drug/infopage/ADHD/default.htm.

Pharmacotherapy for weight loss is recommended only for obese patients with a body mass index 30 kg/m², or 27 kg/m² in the presence of other risk factors such as hypertension, diabetes, and/or dyslipidemia or a high waist circumference; therapy should be used in conjunction with a comprehensive weight management program. Rule out organic causes of obesity (eg, untreated hypothyroidism) prior to use.

Note: Methamphetamine is not approved for long-term use. The limited usefulness of medications in this class should be weighed against possible risks associated with their use. Consult weight loss guidelines for current pharmacotherapy recommendations.

DRUG INTERACTIONS — Substrate of CYP2D6 (major)

(For additional information: Launch Lexi-Interact™ Drug Interactions Program )

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

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

False neurotransmitters (eg, guanethidine, methyldopa): Amphetamines may inhibit the antihypertensive response to these agents; monitor.

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

Sibutramine: Concurrent use of sibutramine and amphetamines may cause severe hypertension and tachycardia; use is contraindicated (benzphetamine)

SSRIs: Amphetamines may increase the potential for serotonin syndrome when used concurrently with selective serotonin reuptake inhibitors (including fluoxetine, fluvoxamine, paroxetine, and sertraline)

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

ETHANOL / NUTRITION / HERB INTERACTIONS Ethanol: Avoid ethanol (may cause CNS depression).

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

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

PREGNANCY RISK FACTOR — C (show table)

PREGNANCY IMPLICATIONS — Teratogenic and embryocidal effects have been observed in animal studies. Infants may deliver prematurely and suffer withdrawal symptoms. There are no adequate and well-controlled studies in pregnant women.

LACTATION — Enters breast milk/contraindicated

DIETARY CONSIDERATIONS — Most effective when combined with a low calorie diet and behavior modification counseling.

MONITORING PARAMETERS — Heart rate, respiratory rate, blood pressure, CNS activity, body weight (BMI); growth rate in children

REFERENCE RANGE Adult classification of weight by BMI (kg/m²):   Underweight: <18.5   Normal: 18.5-24.9   Overweight: 25-29.9   Obese, class I: 30-34.9   Obese, class II: 35-39.9   Extreme obesity (class III): 40

Waist circumference: In adults with a BMI of 25-34.9 kg/m², high-risk waist circumference is defined as:   Men >102 cm (>40 in)   Women >88 cm (>35 in)

TOXICOLOGY / OVERDOSE COMPREHENSIVE — Symptoms include seizures, hyperactivity, coma, and hypertension. There is no specific antidote for amphetamine intoxication and the bulk of treatment is 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. Hyperthermia is best treated with external cooling measures, or when severe or unresponsive, muscle paralysis with pancuronium may be needed. Hypertension is usually transient and generally does not require treatment unless severe. For diastolic blood pressures >110 mm Hg, a nitroprusside infusion should be initiated. Seizures usually respond to diazepam IVP and/or phenytoin maintenance regimens. Agents which enhance urinary acidification (eg, potassium acid phosphate or ammonium chloride) may increase the renal elimination of amphetamines; very large doses may be required.

CANADIAN BRAND NAMES — Desoxyn®

INTERNATIONAL BRAND NAMES — Cidrin (CL); Desoxyn (CA)

MECHANISM OF ACTION — A sympathomimetic amine related to ephedrine and amphetamine with CNS stimulant activity; peripheral actions include elevation of systolic and diastolic blood pressure and weak bronchodilator and respiratory stimulant action

PHARMACODYNAMICS / KINETICS Absorption: Rapid from GI tract

Metabolism: Hepatic; forms metabolite

Half-life elimination: 4-5 hours

Excretion: Urine primarily (dependent on urine pH)

PATIENT INFORMATION — Take during day to avoid insomnia; do not discontinue abruptly, may cause physical and psychological dependence with prolonged use

(For additional information see "Methamphetamine: Patient drug information")

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