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Chapter 36

Chapter 36. Central Nervous System Stimulants and Attention-Deficit/Hyperactivity Disorder. CNS Stimulants. Increase the activity of CNS neurons Enhance neuronal excitation; a few suppress neuronal inhibition In sufficient doses, all can cause convulsions Limited clinical applications.

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Chapter 36

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  1. Chapter 36 Central Nervous System Stimulants and Attention-Deficit/Hyperactivity Disorder

  2. CNS Stimulants • Increase the activity of CNS neurons • Enhance neuronal excitation; a few suppress neuronal inhibition • In sufficient doses, all can cause convulsions • Limited clinical applications

  3. CNS Stimulants and Attention-Deficit/Hyperactivity Disorder • Amphetamines • Methylphenidate and dexmethylphenidate • Methylxanthines • Miscellaneous stimulants • Attention-deficit/hyperactivity disorder (ADHD)

  4. Amphetamines • Chemistry • Dextroamphetamine and levamphetamine • Amphetamine • Lisdexamfetamine • Methamphetamine • Mechanism of action • Release norepinephrine (NE) • Release dopamine (DA)

  5. Amphetamines • Pharmacologic effects • Central nervous system • Cardiovascular system • Tolerance • With regular use, develops to elevation of mood, suppression of appetite, and stimulation of the heart and blood vessels • Physical dependence • Abstinence syndrome with abrupt withdrawal • Abuse • High potential for abuse due to euphoria

  6. Fig. 36–1. Structural formulas of the amphetamines.

  7. Amphetamines • Adverse effects • CNS stimulation • Weight loss • Cardiovascular effects • Psychosis

  8. Amphetamines • Toxicity • Dysrhythmias • Hypertension • Dizziness • Confusion • Hallucinations • Convulsions • Paranoid delusions • Coma • Palpitations • Cerebral hemorrhage

  9. Amphetamines • Treatment • Chlorpromazine: hallucinations • Alpha-adrenergic blocker: hypertension • Diazepam: seizures • Therapeutic uses • ADHD • Narcolepsy

  10. Amphetamines • Preparations, dosage, and administration • Dextroamphetamine sulfate • Short duration (Dexedrine, Dextrostat) • Long duration (Dexedrine Spansules) • Amphetamine/dextroamphetamine mixture • Short duration (Adderall) • Long duration (Adderall-XR) • Methamphetamine (Desoxyn)

  11. Methylphenidate and Dexmethylphenidate • Methylphenidate and dexmethylphenidate are nearly identical in structure and pharmacologic actions • The pharmacology of both drugs is nearly identical to that of amphetamines

  12. Methylphenidate • ADHD and narcolepsy • Trade names • Ritalin, Metadate, Methylin, Concerta, Daytrana • 50:50 mixture of dextro and levo isomers • Preparations, dosage, and administration • Short duration • Ritalin, Methylin • Intermediate duration • Ritalin SR, Metadate ER, Methylin ER • Long duration • Concerta, Metadate CD, Ritalin LA

  13. Dexmethylphenidate (Focalin) • Drug for ADHD • Dextro isomer of methylphenidate • 50:50 mixture of dextro and levo isomers • Schedule II drug

  14. Methylxanthines • Derivatives of xanthine • Caffeine • Few clinical applications • Widespread ingestion for nonmedical purposes • Dietary sources • Chocolate • Desserts • Soft drinks • Cola nut

  15. Methylxanthines • Mechanism of action • Reversible blockade of adenosine receptors • Calcium permeability • Accumulation of cyclic AMP • Low doses • Decrease drowsiness and fatigue and increase capacity for prolonged intellectual exertion • Increasing doses • Nervousness, insomnia, tremors • Seizures with very large amounts AMP = adenosine monophosphate.

  16. Fig. 36–2. Structural formulas of the methylxanthines.

  17. Methylxanthines • Pharmacologic effects • Central nervous system • Heart • Blood vessels • Bronchi • Kidney • Reproduction • Pharmacokinetics • Readily absorbed from the GI tract • Achieve peak plasma levels within 1 hour • Eliminated by hepatic metabolism

  18. Methylxanthines • Therapeutic uses • Neonatal apnea • Promoting wakefulness • Other applications • Acute toxicity • Stimulation of the CNS • Tachycardia • Respiratory stimulation • Sensory phenomena

  19. Methylxanthines • Preparations, dosage, and administration • For promoting wakefulness • For neonatal apnea • Theophylline • Theobromine

  20. Miscellaneous CNS Stimulants • Pemoline • Actions, uses, and adverse effects • Causes less cardiac stimulation and vasoconstriction • Can cause liver failure • Preparations, dosage, and administration

  21. Miscellaneous CNS Stimulants • Modafinil (Provigil, Alertec) • Therapeutic use • Promotes wakefulness • Mechanism of action • Pharmacokinetics • Rapidly absorbed in the GI tract • Elimination by hepatic metabolism • Half-life:about 15 hours

  22. Miscellaneous CNS Stimulants • Modafinil (Provigil, Alertec) (cont’d) • Adverse effects • Headache • Nausea • Nervousness • Diarrhea • Rhinitis • Drug interactions • Oral contraceptives • Cyclosporine

  23. Miscellaneous CNS Stimulants • Modafinil (Provigil, Alertec) (cont’d) • Preparations, dosage, and administration • Blockade • Strychnine: not used as a medicine • Poisoning • Causes: accidental ingestion, street drugs • Symptoms: convulsions, depression • Treatment: intravenous diazepam, general anesthesia, or neuromuscular blocker • Armodafinil • Doxapram • Cocaine

  24. Attention-Deficit/Hyperactivity Disorder (ADHD) in Children • Signs and symptoms • Inattention • Hyperactivity • Impulsivity • Fidgety • Unable to concentrate

  25. ADHD in Children • Signs and symptoms (cont’d) • Unable to wait his or her turn • Switches excessively from one activity to another • Calls out excessively in class • Present before age 7 years • Present for at least 6 months

  26. ADHD in Children • Etiology • Management overview • Cognitive therapy • Stimulant drugs • Drug therapy I: CNS stimulants • Methylphenidate (Ritalin, Concerta, others) • Dexmethylphenidate (Focalin) • Dextroamphetamine (Dexedrine, others) • Amphetamine mixture (Adderall) • Pemoline (Cylert)

  27. ADHD in Children • Drug therapy II: atomoxetine • Description and therapeutic effects • Nonstimulant • No potential for abuse • Administered once a day

  28. ADHD in Children • Drug therapy II: atomoxetine (cont’d) • Mechanism of action • Selective inhibitor of NE reuptake • Pharmacokinetics • Plasma levels peak in 1–3 hours • Metabolized in the liver

  29. ADHD in Children • Drug therapy II: atomoxetine (cont’d) • Adverse effects • GI reactions • Reduced appetite • Dizziness • Somnolence • Mood swings • Trouble sleeping

  30. ADHD in Children • Drug therapy II: atomoxetine (cont’d) • Drug interactions • MAO inhibitors (isocarboxazid, phenelzine) • CYP2D6 (paroxetine, fluoxetine, quinidine) • Role in ADHD therapy • Preparations, dosage, and administration • Children who weigh less than 70 kg • Children who weigh 70 kg or more

  31. ADHD in Children • Drug therapy III: antidepressants • Tricyclic antidepressants • Decrease hyperactivity • Little effect on impulsivity and inattention • Second-line drugs • Bupropion (Wellbutrin) • Can reduce behavioral symptoms • Less effective than stimulants • Poses risk of seizure • Second-line drug

  32. ADHD in Adults • Drug therapy III: antidepressants • 60% of ADHD cases persist into adulthood • Symptoms • Poor concentration • Stress intolerance • Antisocial behavior • Outbursts of anger • Inability to maintain a routine • Drug therapy • Methylphenidate

  33. Drugs Used for ADHD • Drug therapy • Methylphenidate (Ritalin, Concerta) • Dexmethylphenidate (Focalin) • Dextroamphetamine (DextroStat) • Amphetamine mixture (Adderall) • Nonstimulants • Atomoxetine (Strattera) • Guanfacine (Intuniv) • Clonidine (Kapvay)

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