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Department of Pharmacology

Section 4 Drugs Affecting the Center Nervous System. Department of Pharmacology. Chapter 22 Sedative and hypnotic Drugs. Definitions A sedative drug decreases activity, moderates excitement, and calms the recipient.

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Department of Pharmacology

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  1. Section 4 Drugs Affecting the Center Nervous System Department of Pharmacology

  2. Chapter 22 Sedative and hypnotic Drugs

  3. Definitions • A sedative drug decreases activity, moderates excitement, and calms the recipient. • A hypnotic drug produces drowsiness and facilitates the onset and maintenance of a state of sleep that resembles natural sleep, and from which the patient can be easily aroused.

  4. Drugs: • Benzodiazepines (BDZs) • Barbiturates • Others: chloral hydrate • Small dose: sedation • Large dose: hypnosis;anticonvulsant; anesthesia

  5. 苯二氮卓类 (Benzodiazepines BZ) 地西泮（安定） Diazepam 奥沙西泮 Oxazepam 三唑仑 Triazolam

  6. Drugs Elimination half life (hours) Dosage（mg） sedative hypnotic Diazepam 30~60 2.5~5 ,tid 5~10 Oxazepam 5~10 15~30, qd,tid 15~30 Triazolam 1.5~3 - 0.25~0.5（15~30分起效)

  7. Diazepam 地西泮 • （valium, 安定） • Action and use: • Reduction of anxiety The anxiolytic actions can be occurred at lower dosage . lose memory, Preanesthetic medication • Sedative and hypnosis mainly prolong stage 2 of NREMS, shorten REMS and latency of sleep onset

  8. Stages of Sleep When subject falls asleep, EEG progresses through stages: • non-rapid-eye movement sleep, NREMS including 1、2、3、4 stages ，stage 3、4 also called “ Slow wave sleep，SWS” （慢波睡眠） • rapid eye movement sleep, REMS

  9. SLEEP: NREMS REMS NREMS REMS：NS development，memory NREMS： 1,2 stages 3,4 stages (Slow wave sleep，SWS) growth ,restore

  10. Anticonvulsant and antiepileptic action iv diazepam is the best choice for status epilepticus (癫痫持续状态) • Central muscle relaxing treatment for central myotonia (肌强直)caused by cerebral accident(脑血管意外) or spinal cord injury(脊髓损伤)

  11. Mechanism: Promote GABA receptor function • γ- butylamino acid, GABA • GABA A receptor consists of twoα1,two β2 and one γ2 subunits. • GABA A receptor, which functions as a chloride ion channel, is activated by the inhibitory neurotransmitter GABA .

  12. GABA appears to interact with αorβsubunits triggering chloride channel opening with resultant membrane hyperpolarization. • The binding site for BDZs (BDZ-receptor) is located between αandγsubunit.

  13. BDZs appear to increase the efficiency of GABAergic synaptic inhibition. • The enhancement in chloride ion conductance induced by the interaction of BDZs with GABA takes the form of an increase in the frequency of channel-opening events.

  14. Side effects: • common: hypersomnia, drowsiness, ataxia, impaired judgment, diminished motor skills. • iv too fast cause CNS depression • rarely fatal even following very high doses. Except: the presence of other central nervous system depressants; child, elder patients；patients with severe liver disease

  15. Treatment of toxicosis: • Ensuring the living symptom • Maintenance of plasma volume, renal output, cardiac function • purging the stomach；Hemodialysis • BDZreceptor antagonist flumazenil (氟马西尼,安易行） • Tolerance and addiction • Fetal deformation

  16. Barbiturates Classification: Drug t½(h)onset duration (h) Phenobarbital 24-140 + 6-8 (luminal,苯巴比妥) Amobarbital 8-42 ++ 3-6 (amytal,异戊巴比妥) Secobarbital（司可巴比妥）19-34 +++ 2-3 Thiopental（硫喷妥 ）3-8 ++++ 1-4

  17. Action and use: • sedative and hypnosis • shorten REMS • dose dependence • anticonvulsant(phenobarbital) • anesthesia and preanestheticmedication (thiopental) • enhance CNS depression

  18. Mechanism • It can activate GABAA receptor, potentiate GABA action on chloride entry into the neuron. • Barbiturates: increase the open timeofCl-channel • BZ: increase the open frequencyofCl- channel

  19. Adverse effect • drug hangover: tiredness after awakes • tolerance: induce P-450 system • addiction: abrupt withdrawal may cause • tremor, anxiety, weakness, restlessness, • nausea and vomiting • respiratory depression • allergy

  20. Poisoning Poisoning: overdoses can cause death, depression of respiration and central cardiovascular depression. Treatment: artificial respiration; purging the stomach of its contents; alkalinization of blood and urine; hemodialysis

  21. BDZ’s ADVANTAGE: • therapeutic index high, safe range broad • no inductive effects on P-450 system, less tolerance • less effects on REMS, dependence, withdraw syndrome slight • side effects mild • BZreceptor antagonist —— flumazenil 氟马西尼

  22. Other sedatives Chloral hydrate水合氯醛 induces sleep in about 15 minutes and lasts 6~8 hours. irritates to the gastrointestinal tract and causes epigastric distress, also produces an unusual, unpleasant taste sensation.

  23. Central stimulants • Stimulating cerebral cortex: Caffeine 咖啡因 Theophylline 茶碱 • Stimulating medullary respiratory center 延髓呼吸中枢 Nikethamide 尼可刹米 Lobeline 洛贝林

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