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Chapter 16 Sedatives and Hypnotics

Chapter 16 Sedatives and Hypnotics. Graded dose-dependent depression of central nervous system function is a charicteristic of sedative-hypnotics. Classification of drugs Benzodiazepines are the most important sedative-hypnotics. Barbiturates Other agents. Sub-classify of Benzodiazepines.

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Chapter 16 Sedatives and Hypnotics

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  1. Chapter 16 Sedatives and Hypnotics • Graded dose-dependent depression of central nervous system function is a charicteristic of sedative-hypnotics. • Classification of drugs • Benzodiazepines are the most important sedative-hypnotics. • Barbiturates • Other agents

  2. Sub-classify of Benzodiazepines • Short-acting(t1/2<6 hours) • Triazolam（三唑仑） • intermediate -acting(t1/2 6~24 hours) • Oxazepam(奥沙西泮），nitrazepam（硝基安定） • long-acting(t1/2>24 hours) • Diazepam(地西泮,安定）,flurazepam（氟西泮，氟安定）,and chlordiazepoxide（氯氮卓）

  3. Benzodiazepines Diazepam(地西泮） [Pharmacological effects and clinical uses] • 1. Antianxiety • Diazepam reduces anxiety at doses that do not produce sedation. • This action is related to selective inhibition of neuronal circuits in the limbic边缘 system of the brain. • 2. Sedative and hypnosis • It shortens the latency潜伏期 of sleep onset,decreases intermittent awakening and prolongs the duration of sleep.

  4. Benzodiazepines • 3. Anticonvulsant effects and antiepileptic effects Benzodiazepines are capable of inhibting the development and spread of epileptic form activity in the central nervous system. • 4.Muscle relaxation • The mechanism is that it exerts inhibitory effects on polysynaptic reflexes and internuncial transmission,and at high doses may depress transmission at the skeletal myoneural junction.

  5. Benzodiazepines Therapeutic applications • Anxiety disorders • Insomnia失眠 • Anticonvulsion and antiepilepsy • Muscle disorders

  6. Benzodiazepines [Mechanism of actions] • GABAA receptor has a structure comprised of multiple subunits( alpha, beta,gamma, etc). Combinations of the three major subunits appear to be essential for normal physiologic and pharmacologic function of the macromolecule. • GABA binds to receptor sites on the beta subunits and that this interaction initiates gating of the chloride channel current. • The benzodiazepine receptor sites are probably located on alpha subunits. Benzodiazepine drugs can binds to these sites,but they don’t substitute for GABA. They appear to enhance GABA’effects without directly activating GABA receptors or opening the associated chloride channels. • The enhancement in chloride ion conductance induced by the interaction of benzodiazepines with GABA takes the form of an increase in the frequency of channel opening events. This effect may be due in part to enhanced receptor affinity for GABA.

  7. 安定的作用机制 安定 BZ受体 GABA受体调控蛋白变构 GABA激活GABAA受体 Cl-通道开放 Cl-内流 细胞超极化

  8. Benzodiazepines [Adverse effects] • Many of the common adverse effects of drugs in this class are those resulting from dose-related depression of central nervous system functions. • Relatively low doses may lead to drowsiness思睡, impaired judgment,and diminished motor skills etc. • At toxic doses,sedative-hypnotics can produce significant respiratory and cardiovascular depression. • Physical and psychological dependence can develop when diazepam is taken for a long period. Rebound and abstinence signs include anxiety, insomnia, tension, tremor震颤 and seizure.

  9. Barbiturates • long-acting • Phenobarbital 苯巴比妥（鲁米那） • intermediate –acting • Pentobarbital戊巴比妥，Amobarbital异戊巴比妥 • Short-acting • Secobarbital 司可巴比妥 • Ultra- short-acting • Thiopental 硫喷妥钠

  10. Barbiturates Pharmacological effects and Therapeutic applications • As the dose increases, Barbiturates have : • Sadation and hypnosis • Anticonvulsion and antiepilepsy • Anaesthesia and pre-anaesthesia medication.

  11. Barbiturates [Mechanism of actions] • Barbiturates also facilitate the actions of GABA at multiple sites in the central nervous system. But in contrast to benzodiazepines, on different site , Barbiturates prolong the duration of the GABA-gated channel (chloride channels) openings. • Barbiturates can reduce glutamate induced depolarization and inhibit Na+and K+ channel at higher concentrations. • Barbiturates depress the reticular ascending activating system at sedative-hypnotic concentrations.

  12. Barbiturates [Adverse effects] • Hangover宿睡 • Drug tolerance-dependence • Acquired hypersensitivity • Poisoning

  13. Other agents • Chloral hydrate（水合氯醛）

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