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Methamphetamine

Pronunciation

Pronunciation

(meth am FET a meen)

Index Terms

  • Desoxyephedrine Hydrochloride
  • Methamphetamine Hydrochloride

Dosage Forms

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

Tablet, Oral, as hydrochloride:

Desoxyn: 5 mg [contains sodium aminobenzoate]

Generic: 5 mg

Brand Names: U.S.

  • Desoxyn

Pharmacologic Category

  • Anorexiant
  • Central Nervous System Stimulant
  • Sympathomimetic

Pharmacology

A sympathomimetic amine related to ephedrine and amphetamine with CNS stimulant activity; causes release of catecholamines (primarily dopamine and other catecholamines) from their storage sites in the presynaptic nerve terminals. Inhibits reuptake and metabolism of catecholamines through inhibition of monoamine transporters and oxidase.

Absorption

Rapid from GI tract

Metabolism

Predominately hepatic via aromatic hydroxylation, N-dealkylation and deamination; forms ≥7 metabolites

Excretion

Urine primarily (dependent on urine pH; alkaline urine increases the half-life); 62% of dose eliminated within first 24 hours as ~33% unchanged drug with remainder as metabolites

Half-Life Elimination

4-5 hours

Use: Labeled Indications

Attention-deficit/hyperactivity disorder (ADHD): For a stabilizing effect in children >6 years with a behavioral syndrome characterized by the following group of developmentally inappropriate symptoms: Moderate to severe distractibility, short attention span, hyperactivity, emotional lability, and impulsivity

Exogenous obesity: Short-term (ie, a few weeks) adjunct in a regimen of weight reduction based on caloric restriction, for patients in whom obesity is refractory to alternative therapy (eg, repeated diets, group programs, other drugs)

Use: Unlabeled

Narcolepsy

Contraindications

During or within 14 days following MAO inhibitors; glaucoma; advanced arteriosclerosis; symptomatic cardiovascular disease; moderate to severe hypertension; hyperthyroidism; hypersensitivity or idiosyncrasy to sympathomimetic amines; agitated state; patients with a history of drug abuse

Documentation of allergenic cross-reactivity for amphetamines is limited. However, because of similarities in chemical structure and/or pharmacologic actions, the possibility of cross-sensitivity cannot be ruled out with certainty.

Dosing: Adult

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

Narcolepsy (off-label use): Oral: 20 to 60 mg administered within 1 hour of awakening (Mitler 1993). Additional data may be necessary to further define the role of methamphetamine in this condition.

Dosing: Geriatric

Refer to adult dosing.

Dosing: Pediatric

ADHD: Oral: Children ≥6 years: Initial: 5 mg 1-2 times daily; may increase by 5 mg increments at weekly intervals until optimum response is achieved; usual effective dose range: 20-25 mg daily in 1 or 2 divided doses

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

Dosing: Renal Impairment

No dosage adjustment provided in manufacturer’s labeling.

Dosing: Hepatic Impairment

No dosage adjustment provided in manufacturer’s labeling.

Administration

For obesity, administer 30 minutes before each meal. Late evening doses should be avoided due to potential for insomnia.

Dietary Considerations

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

Storage

Store below 30°C (86°F).

Drug Interactions

Abiraterone Acetate: May increase the serum concentration of CYP2D6 Substrates. Management: Avoid concurrent use of abiraterone with CYP2D6 substrates that have a narrow therapeutic index whenever possible. When concurrent use is not avoidable, monitor patients closely for signs/symptoms of toxicity. Consider therapy modification

Acebrophylline: May enhance the stimulatory effect of CNS Stimulants. Avoid combination

Ajmaline: May increase the serum concentration of CYP2D6 Substrates. Monitor therapy

Alkalinizing Agents: May decrease the excretion of Amphetamines. Consider therapy modification

Ammonium Chloride: May decrease the serum concentration of Amphetamines. This effect is likely due to an enhanced excretion of amphetamines in the urine. Monitor therapy

Analgesics (Opioid): Amphetamines may enhance the analgesic effect of Analgesics (Opioid). Monitor therapy

Antacids: May decrease the excretion of Amphetamines. Monitor therapy

Antihistamines: Amphetamines may diminish the sedative effect of Antihistamines. Monitor therapy

Antihypertensive Agents: Amphetamines may diminish the antihypertensive effect of Antihypertensive Agents. Monitor therapy

Antipsychotic Agents: May diminish the stimulatory effect of Amphetamines. Monitor therapy

Ascorbic Acid: May decrease the serum concentration of Amphetamines. Monitor therapy

Asunaprevir: May increase the serum concentration of CYP2D6 Substrates. Consider therapy modification

AtoMOXetine: May enhance the hypertensive effect of Sympathomimetics. AtoMOXetine may enhance the tachycardic effect of Sympathomimetics. Monitor therapy

Cannabinoid-Containing Products: May enhance the tachycardic effect of Sympathomimetics. Exceptions: Cannabidiol. Monitor therapy

Carbonic Anhydrase Inhibitors: May decrease the excretion of Amphetamines. Exceptions: Brinzolamide; Dorzolamide. Monitor therapy

Cobicistat: May increase the serum concentration of CYP2D6 Substrates. Monitor therapy

CYP2D6 Inhibitors (Moderate): May decrease the metabolism of CYP2D6 Substrates. Monitor therapy

CYP2D6 Inhibitors (Strong): May decrease the metabolism of CYP2D6 Substrates. Consider therapy modification

Darunavir: May increase the serum concentration of CYP2D6 Substrates. Monitor therapy

Doxofylline: Sympathomimetics may enhance the adverse/toxic effect of Doxofylline. Monitor therapy

Ethosuximide: Amphetamines may diminish the therapeutic effect of Ethosuximide. Amphetamines may decrease the serum concentration of Ethosuximide. Monitor therapy

Gastrointestinal Acidifying Agents: May decrease the serum concentration of Amphetamines. Monitor therapy

Imatinib: May increase the serum concentration of CYP2D6 Substrates. Monitor therapy

Iobenguane I 123: Sympathomimetics may diminish the therapeutic effect of Iobenguane I 123. Avoid combination

Ioflupane I 123: Amphetamines may diminish the diagnostic effect of Ioflupane I 123. Monitor therapy

Linezolid: May enhance the hypertensive effect of Sympathomimetics. Management: Reduce initial doses of sympathomimetic agents, and closely monitor for enhanced pressor response, in patients receiving linezolid. Specific dose adjustment recommendations are not presently available. Consider therapy modification

Lithium: May diminish the stimulatory effect of Amphetamines. Monitor therapy

Lumefantrine: May increase the serum concentration of CYP2D6 Substrates. Monitor therapy

MAO Inhibitors: May enhance the hypertensive effect of Amphetamines. While linezolid and tedizolid may interact via this mechanism, management recommendations differ from other monoamine oxidase inhibitors. Refer to monographs specific to those agents for details. Exceptions: Linezolid; Tedizolid. Avoid combination

Methenamine: May decrease the serum concentration of Amphetamines. This effect is likely due to an enhanced excretion of amphetamines in the urine. Monitor therapy

Multivitamins/Fluoride (with ADE): May decrease the serum concentration of Amphetamines. More specifically, the ascorbic acid (vitamin C) in many multivitamins may decrease amphetamine concentrations. Monitor therapy

Multivitamins/Minerals (with ADEK, Folate, Iron): May decrease the serum concentration of Amphetamines. Monitor therapy

Multivitamins/Minerals (with AE, No Iron): May decrease the serum concentration of Amphetamines. Specifically, vitamin C may impair absorption of amphetamines. Monitor therapy

Panobinostat: May increase the serum concentration of CYP2D6 Substrates. Management: Avoid concurrent use of sensitive CYP2D6 substrates when possible, particularly those substrates with a narrow therapeutic index. Consider therapy modification

Peginterferon Alfa-2b: May decrease the serum concentration of CYP2D6 Substrates. Peginterferon Alfa-2b may increase the serum concentration of CYP2D6 Substrates. Monitor therapy

Perhexiline: CYP2D6 Substrates may increase the serum concentration of Perhexiline. Perhexiline may increase the serum concentration of CYP2D6 Substrates. Monitor therapy

PHENobarbital: Amphetamines may decrease the serum concentration of PHENobarbital. Monitor therapy

Phenytoin: Amphetamines may decrease the serum concentration of Phenytoin. Monitor therapy

QuiNINE: May increase the serum concentration of CYP2D6 Substrates. Monitor therapy

Sympathomimetics: May enhance the adverse/toxic effect of other Sympathomimetics. Monitor therapy

Tedizolid: May enhance the hypertensive effect of Sympathomimetics. Tedizolid may enhance the tachycardic effect of Sympathomimetics. Monitor therapy

Tricyclic Antidepressants: May enhance the stimulatory effect of Amphetamines. Tricyclic Antidepressants may also potentiate the cardiovascular effects of Amphetamines. Monitor therapy

Urinary Acidifying Agents: May decrease the serum concentration of Amphetamines. Monitor therapy

Test Interactions

Amphetamines may elevate plasma corticosteroid levels; may interfere with urinary steroid determinations.

Adverse Reactions

Frequency not defined.

Cardiovascular: Hypertension, increased blood pressure, palpitations, tachycardia

Central nervous system: Dizziness, drug dependence (prolonged use), dysphoria, euphoria, exacerbation of tics (motor, phonic, and Tourette's syndrome), headache, insomnia, overstimulation, psychotic symptoms, restlessness

Dermatologic: Urticaria

Endocrine & metabolic: Change in libido, growth suppression (children)

Gastrointestinal: Constipation, diarrhea, gastrointestinal distress, unpleasant taste, xerostomia

Genitourinary: Frequent erections, impotence, prolonged erection

Neuromuscular & skeletal: Rhabdomyolysis, tremor

ALERT: U.S. Boxed Warning

Abuse potential:

Methamphetamine has a high potential for abuse. Pay particular attention to the possibility of subjects obtaining methamphetamine for nontherapeutic use or distribution to others; the drug should be prescribed or dispensed sparingly. Misuse of methamphetamine may cause sudden death and serious cardiovascular adverse events.

Weight reduction:

Methamphetamine should be tried only in weight reduction programs for patients in whom alternative therapy has been ineffective. Administration of methamphetamine for prolonged periods of time in obesity may lead to drug dependence and must be avoided.

Warnings/Precautions

Concerns related to adverse effects:

• Cardiovascular events: CNS stimulant use has been associated with serious cardiovascular events including sudden death in patients with preexisting 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, Marfan syndrome, 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. Patients who develop angina, unexplained syncope, or other symptoms of cardiac disease during therapy should be evaluated immediately.

• CNS effects: Amphetamines may impair the ability to engage in potentially hazardous activities; patients must be cautioned about performing tasks which require mental alertness (eg, operating machinery or driving).

• Peripheral vasculopathy: Stimulants are associated with peripheral vasculopathy, including Raynaud’s phenomenon; signs/symptoms are usually mild and intermittent, and generally improve with dose reduction or discontinuation. Digital ulceration and/or soft tissue breakdown have been observed rarely; monitor for digital changes during therapy and seek further evaluation (eg, rheumatology) if necessary.

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

Disease-related concerns:

• Abuse potential: [U.S. Boxed Warning]: Potential for drug dependency and abuse exists. Misuse has resulted in death including fatal cardiorespiratory arrest. Use is contraindicated in patients with history of drug abuse. Prescriptions should be written for the smallest quantity consistent with good patient care to minimize possibility of overdose.

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

• Hypertension: Use with caution in patients with hypertension and other cardiovascular conditions (heart failure, recent MI, ventricular arrhythmia) 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 preexisting 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. Patients should be screened for bipolar disorder prior to treatment; consider discontinuation if such symptoms (eg, delusional thinking, hallucinations, or mania) occur. May be associated with aggressive behavior or hostility (causal relationship not established); monitor for development or worsening of these behaviors.

• 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. Discontinue use if seizures occur.

• Tourette's syndrome: Use with caution in patients with Tourette's syndrome; stimulants may exacerbate motor and phonic tics and Tourette’s syndrome.

Special populations:

• Elderly: Use caution in this age group due to the risk for causing dependence, hypertension, angina, and myocardial infarction.

• Pediatric: Use of stimulants has been associated with suppression of growth; monitor growth rate during treatment.

Other warnings/precautions:

• ADHD treatment: Appropriate use: Recommended to be used as part of a comprehensive treatment program for attention deficit disorders. Aggression and hostility has been reported with use of medications for ADHD treatment; no evidence suggests that stimulants cause aggressive behavior but patient should be monitored for the onset or exacerbation of these behaviors.

• 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.

• Inappropriate use: Therapy is not appropriate for the treatment of fatigue in normal patients.

• Weight reduction: Appropriate use: [U.S. Boxed Warning]: Use in weight reduction programs only when alternative therapy has been ineffective. Avoid prolonged treatment durations due to potential for drug dependence. Tolerance to the anorectic effect generally develops with a few weeks; when tolerance develops, discontinue therapy rather than increase the dose in an attempt to increase the effect.

Monitoring Parameters

Heart rate, respiratory rate, blood pressure, CNS activity, body weight (BMI), signs of peripheral vasculopathy (eg, digital changes); growth rate in children

When used for the treatment of ADHD, thoroughly evaluate for cardiovascular risk. Monitor heart rate, blood pressure, and consider obtaining ECG prior to initiation (Vetter, 2008). Monitor for aggression and hostility.

Pregnancy Risk Factor

C

Pregnancy Considerations

Adverse effects have been observed in animal reproduction studies. Methamphetamine and amphetamine were detected in newborn tissues following intermittent maternal use of Desoxyn during pregnancy (Garriott, 1973). The majority of human data is based on illicit amphetamine/methamphetamine exposure and not from therapeutic maternal use (Golub, 2005). Use of amphetamines during pregnancy may lead to an increased risk of premature birth and low birth weight; newborns may experience symptoms of withdrawal. Behavioral problems may also occur later in childhood (LaGasse, 2012).

Patient Education

• Discuss specific use of drug and side effects with patient as it relates to treatment. (HCAHPS: During this hospital stay, were you given any medicine that you had not taken before? Before giving you any new medicine, how often did hospital staff tell you what the medicine was for? How often did hospital staff describe possible side effects in a way you could understand?)

• Patient may experience dry mouth, insomnia, constipation, diarrhea, bad taste, lack of appetite, nausea, or weight loss. Have patient report immediately to prescriber signs of severe cerebrovascular disease (change in strength on one side is greater than the other, trouble speaking or thinking, change in balance, or change in eyesight), angina, shortness of breath, severe dizziness, passing out, tachycardia, arrhythmia, tremors, agitation, severe anxiety, severe headache, sexual dysfunction, decreased libido, priapism, seizures, discoloration of hands or feet, burning or numbness of hands or feet, wounds on fingers or toes, dark urine, urinary retention, change in amount of urine passed, muscle pain, muscle weakness, mood changes, hallucinations, behavioral changes, or signs of depression (suicidal ideation, anxiety, emotional instability, illogical thinking) (HCAHPS).

• Educate patient about signs of a significant reaction (eg, wheezing; chest tightness; fever; itching; bad cough; blue skin color; seizures; or swelling of face, lips, tongue, or throat). Note: This is not a comprehensive list of all side effects. Patient should consult prescriber for additional questions.

Intended Use and Disclaimer: Should not be printed and given to patients. This information is intended to serve as a concise initial reference for health care professionals to use when discussing medications with a patient. You must ultimately rely on your own discretion, experience, and judgment in diagnosing, treating, and advising patients.

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