Methamphetamine

# Methamphetamine ## Overview - **Classification**: Central Nervous System (CNS) Stimulant; Sympathomimetic Amine - **Mechanism**: Blocks reuptake of norepinephrine and dopamine, leading to increased release of these monoamines into the extraneuronal space. Also inhibits monoamine oxidase. ## Primary Indications 1. **Attention Deficit Hyperactivity Disorder (ADHD)** - Adjunctive treatment for behavioral management in children (≥6 years) and adults. 2. **Exogenous Obesity** - Short-term (few weeks) adjunct in a regimen of weight reduction based on caloric restriction. ## Adult Dosing ### Standard Dosing **Attention Deficit Hyperactivity Disorder (ADHD)** - **Dose**: Initial **5 mg** - **Frequency**: Once or twice daily - **Route**: Oral - **Titration**: Increase by **5 mg** increments weekly. - **Maximum**: **20-25 mg/day** in divided doses. **Exogenous Obesity** - **Dose**: **5 mg** - **Frequency**: 30 minutes before each meal, or **10-15 mg** once daily in the morning. - **Route**: Oral - **Duration**: Short-term, usually only a few weeks. - **Maximum**: **10-15 mg/day**. ### Dose Adjustments - **Renal Impairment**: Caution advised; monitor for increased effects due to renal elimination. Specific adjustments not well-defined. - **Hepatic Impairment**: No specific guidance; use with caution. - **Elderly Patients**: Generally not recommended due to increased risk of cardiovascular adverse effects. If used, start low and titrate slowly. ## Pediatric Dosing ### Neonates (0-28 days) - **Not approved**: Methamphetamine is not approved for use in neonates. ### Infants (1-12 months) - **Not approved**: Methamphetamine is not approved for use in infants. ### Children (1-12 years) **Attention Deficit Hyperactivity Disorder (ADHD)** - (≥6 years old) - **Dose**: Initial **2.5 mg** - **Frequency**: Once or twice daily. - **Route**: Oral - **Titration**: Increase by **2.5-5 mg** increments weekly. - **Maximum**: **20-25 mg/day** in divided doses. - **Special Notes**: Consider drug holidays to assess growth and dependence. Formulations are oral tablets. ### Adolescents (13-18 years) **Attention Deficit Hyperactivity Disorder (ADHD)** - **Dose**: Follow adult dosing guidelines. Initial **5 mg** once or twice daily. - **Frequency**: Once or twice daily. - **Route**: Oral - **Maximum**: **20-25 mg/day**. - **Special Notes**: Closely monitor growth and weight. Assess for psychiatric adverse effects. ## Safety Information ### Contraindications - **Absolute**: Advanced arteriosclerosis, symptomatic cardiovascular disease, moderate-severe hypertension. - **Absolute**: Hyperthyroidism, glaucoma, agitated states, history of drug abuse. - **Absolute**: Concurrent use or within 14 days of monoamine oxidase inhibitors (MAOIs). - **Absolute**: Hypersensitivity or idiosyncratic reactions to sympathomimetic amines. ### Common Adverse Effects - **Very Common (>10%)**: Insomnia, restlessness, dry mouth, anorexia, weight loss. - **Common (1-10%)**: Tachycardia, palpitations, elevated blood pressure, tremor, headache, dizziness, GI upset. - **Serious but Rare**: Psychotic episodes (especially in predisposed patients), growth suppression (children), cardiomyopathy, serotonin syndrome (with other serotonergic drugs). ### Key Drug Interactions - **MAOIs**: Risk of hypertensive crisis (contraindicated). - **Tricyclic Antidepressants (TCAs)**: Potentiated cardiovascular effects due to enhanced norepinephrine release. - **Antihypertensives**: Reduced hypotensive effect due to sympathomimetic action. - **Urinary Alkalinizers (e.g., Sodium Bicarbonate)**: Increases reabsorption and prolongs half-life, potentially increasing toxicity. - **Urinary Acidifiers (e.g., Ammonium Chloride)**: Increases excretion and decreases half-life, reducing efficacy. ## Monitoring & Follow-up - **Before Treatment**: Baseline blood pressure (BP), heart rate (HR), height/weight (pediatrics), cardiovascular history, psychiatric evaluation. - **During Treatment**: Regular BP and HR monitoring (e.g., at each visit). Monitor height and weight in pediatric patients (at least every 6 months). Assess for psychiatric symptoms (agitation, psychosis, tics). - **Clinical Signs**: Watch for signs of cardiovascular issues (chest pain, syncope, severe palpitations), new or worsening psychiatric symptoms, or persistent growth/weight suppression. ## Clinical Pearls - 💡 **Abuse Potential**: High potential for abuse and dependence. Prescribe with caution, especially for patients with a history of substance use disorder. - 💡 **Administration Timing**: To minimize insomnia, avoid administering the last dose late in the day (e.g., after 4 PM). - 💡 **Growth Monitoring**: In children, monitor height and weight carefully. Consider drug holidays if growth suppression is observed. - 💡 **Withdrawal**: Abrupt discontinuation after prolonged high-dose therapy can lead to extreme fatigue and depression. Taper slowly. > **⚠️ Important**: This information is for educational purposes only. Always consult current prescribing information, local guidelines, and clinical judgment before prescribing.