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CNS Depressants

CNS Depressants. Concepts, principles, and examples. Terms and concepts. Depressant, sedative, tranquillizer, anxiolytic, hypnotic Levels of sedation: Conscious levels: Anxiolytic, behavioral disinhibition, sedation Unconscious levels: Hypnagogic state, sleep, anaesthesia, coma.

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CNS Depressants

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  1. CNS Depressants Concepts, principles, and examples

  2. Terms and concepts • Depressant, sedative, tranquillizer, anxiolytic, hypnotic • Levels of sedation: • Conscious levels: Anxiolytic, behavioral disinhibition, sedation • Unconscious levels: Hypnagogic state, sleep, anaesthesia, coma.

  3. Julien’s principles of CNS depressants • CNS depressants are additive with each other and with the behavioral state of the user. Supradditive = synergistic. • CNS depressants are antagonists of the behavioral stimulants, but in a non-specific fashion. • Rebound or withdrawal is unlikely after a single dose of a CNS depressant. • Dependence, psychological dependence, and tolerance do occur to CNS depressants.

  4. Mechanisms of action • Reversible depression of excitable tissue: barbiturates and non-barbiturates, ethyl alcohol, and general anaesthetics. • Greater depression of polysynaptic pathways, such as the reticular activating system (RAS). • Potentiating the GABAA receptor complex: barbiturates prolong Cl- access 4 to 5 times.

  5. 1. General appearance 2. Sensorium a. Orientation b. Clarity/cloudiness 3. Behavior/manner 4. Stream of talk 5. Cooperativeness 6. Mood (Feeling) 7. Affect (expression) 8. Perception a. Illusions b. Hallucinations 9. Logical thought? 10. Knowledge 11. Intellect function 12. Insight/judgment The mental status exam

  6. General CNS depressants • Barbiturates: A family of over 2500 derivatives of barbituric acid, of which about 50 have been marketed. First used in 1912 (phenobarbital). • Nonbarbiturate hypnotics: Early 1950s • Tranquillizers • General anaesthetics • Abused inhalants

  7. The barbiturates • Pharmacological phenomena • Pharmacokinetics • Ultra-short acting: Short (re)distribution half-lives • Short- to long-acting: Long elimination half-lives • Low selectivity and low TI • Sleep abnormalities • REM suppression • REM rebound and rescidivism

  8. Barbiturates, continued • Psychopharmacological phenomena • Repeated use leads to tolerance and dependence • Individual reactions may be be different from sedation: depression, agitation, and aggressive behavior may occur, influenced by • mental set • social setting • pain • Affects movement and judgment like alcohol

  9. Nonbarbiturate hypnotics • Glutethimide (Doriden), ethchlorvynol (Placidyl), and methyprylon (Noludar) in early 1950s • The methaqualone (Quaalude) episode: • 1951: Malaria treatment • 1965: Tranquillizer and panacea • 1972-73: Abuse epidemic • 1973: Placed on Schedule II • 1984: Withdrawn from market by manufacturer

  10. Antianxiety agents • Dicarbamate derivatives • Meprobamate (Equanil, Miltown) • Mebutamate (Capla), tybamate (Solacen) • Carisoprodol (Rela, Soma) • Benzodiazepines

  11. General anaesthetics • Membrane fluidization and ion channel perturbation • Gas: Nitrous oxide • Volatile liquids: • Ether • Halothane • -fluranes ( iso-, des-, en-, and sevo-) • Injectable GABA agonists • Barbiturates, propofol (Diprovan), etomidate

  12. The GABAA Receptor Complex Cl- Cl- Cl- Cl- Cl- Inside Cl- ion channel B A R B B A R B G A B A G A B A Cl- E t O H Cl- B D Z Cl- Cl- Cl- Cl- Outside

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