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Newer CNS depressants

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Newer CNS depressants. Benzodiazepines, second generation ... Panic attacks and phobias: alprazolam (Xanax) Alcohol withdrawal and abstinence. Antiepileptic ... – PowerPoint PPT presentation

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Title: Newer CNS depressants


1
Newer CNS depressants
  • Benzodiazepines, second generation anxiolytics,
    and antiepileptic drugs

2
Use of benzodiazepines
  • Not for chronic anxiety disorders
  • Not for the elderly
  • Not for depression
  • For short-term treatment of stress-related
    anxiety
  • Acute situational grief
  • Acute stress reactions
  • Short-term anxiety-induced insomnia

3
Pharmacodynamics
  • GABAA receptor interactions
  • Benzodiazepine agonists, eg. diazepam
  • Benzodiazepine antagonists, eg. flumazenil
  • Chloride ion channels and fast IPSPs
  • GABAB receptor interactions
  • Presynaptic for several neurotransmitters
  • Potassium ion channels and late IPSPs
  • Baclofen, a muscle relaxant and antispastic

4
Localized pharmacodynamics
  • Low-dose antianxiety effects hippocampus and
    amygdala
  • Mental confusion and amnesia hippocampus and
    cerebral cortex
  • Sedative-hypnotic effects cerebral cortex
  • Different benzodiazepines have different relative
    effects, perhaps due to multiple subtypes of
    GABAA receptors.

5
Pharmacokinetics
  • Study administration, absorption and distribution
    in textbook.
  • Metabolism is unusual
  • Intermediate metabolites may be psychoactive.
  • Intermediate metabolites may be long-lasting.
  • Elderly patients have difficulty metabolizing
    long-acting benzodiazepines, leading to profound
    dementia. May take 60 days to clear.

6
Uses and side effects of benzodiazepines
  • Panic attacks and phobias alprazolam (Xanax)
  • Alcohol withdrawal and abstinence
  • Antiepileptic
  • Dose-related side effects
  • Drug-induced brain syndrome
  • Impaired functioning
  • Amnesia
  • Severe interactions with alcohol

7
Benzodiazepine miscellany
  • Fetal effects have been reported for BDZ taken in
    the first trimester, but other research disputes
    the claim.
  • If abused, BDZs are part of polydrug abuse,
    complicating flumazenil antagonistic effects
  • GABAA antagonists may enhance learning by
    facilitating cortical and hippocampal cholinergic
    activity
  • GABAB antagonists may enhance cognition and
    counter depression

8
Second generation anxiolytics
  • Zolpidem (Ambien, 1993) Not a BDZ, it is a
    specific agonist at GABAA1 receptors.
  • Rapid uptake and short elimination half-life make
    it an effective insomnia treatment
  • Little interference with normal sleep cycle
  • Safe, and high doses trigger vomiting
  • High doses produce problems in older people
  • Flumazenil antagonizes zolpidem

9
Second generation anxiolytics
  • Buspirone (BuSpar) A weak agonist of 5-HT1A
    receptors, so no crossing or synergy with other
    CNS depressants
  • Buspirone is also antidepressant
  • No sedation, little amnesia or confusion
  • Very slow development of main effect several
    weeks tid. Minimal abuse, withdrawal symptoms.
  • Useful for GAD and anxiety in older people.
  • Postsynaptic inhibition of adenyl cyclase
  • Presynaptic inhibition of 5-HT synthesis
  • Remember grapefruit juice effect on buspirone

10
Controversial anti-anxiety drugs
  • Triazolam (Halcion)
  • Flunitrazepam (Rohypnol)
  • Illegal in U.S.A.
  • Produces amnesia
  • Synergistic with alcohol Date-rape drug
  • Roughies, roofies, rochas

11
Future directions in anxiety control
  • Find partial agonists of BDZ receptors
  • Abecarnil, used for GAD
  • Find drugs which act on different receptor
    subtypes, like Zolpidem
  • Alpidem acts on GABA A1 and GABA A3 sites
  • Imidazenil has fewer side effects
  • Nonhormonal neurosteroids (epalons) as GABAA
    agonists Ganaxolone
  • Serotonin (5HT1A) agonists, like buspirone
    gepirone, alnespirone, ipsapirone

12
Antiepileptic drugs
  • Epileptic seizures, foci/lesions, and kindling
  • Sodium channel blocking
  • carbamazepine, phenytoin (Dilantin)
  • lamotrigine, valproate/valproic acid
  • GABA agonism
  • reduce metabolism of GABA
  • facilitate GABA release gabapentin
  • Enhance GABA action benzodiazepines, valproic
    acid

13
Other uses of antiepileptics
  • Kindling may be part of a set of psychiatric
    disorders characterized by impulse control
    difficulty.
  • Bipolar Disorder and mania
  • Conduct Disorder
  • Borderline Personality Disorder
  • Panic Disorder
  • Intermittent Explosive Disorder
  • Antiepileptic drugs are sometimes helpful.

14
Antiepileptic drugs
  • Identify the three main groups of antiepileptic
    drugs.
  • In which group would you place carbamazepine and
    valproic acid?
  • Construct a timeline of the drug treatment of
    seizure disorders, starting with bromide.
  • How do antiepileptic drugs relate to specific
    psychological disorders?
  • http//www.pslgroup.com/dg/2d9a6.htm
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