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Pharmacology - Sedative-Hypnotic drugs

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What is the GABAa receptor?
a chloride channel
What happens when the GABAa receptor is stimulated?
the chloride channel opens, chloride enters the cell, and it becomes hyperpolarized
Where do benzodiazepines (BDZs) bind?
to an allosteric site on the GABAa receptor
What is the effect of BDZ binding to the GABAa receptor?
they increase the frequency of opening of the chloride channels, increasing the amplitude of the IPSP
Which is safer: BDZs or barbiturates? Why?
BDZs, they have fewer side effects (esp. respiratory depression)
How are BDZs administered and where are they metabolized?
orally; in the liver
BDZs are dangerous when taken in combination with what?
alcohol or other CNS depressants
Sudden withdrawal of BDZs after prolonged use may cause what?
SEIZURES and psychosis
Which drugs decrease the metabolism of BDZs, thereby increasing their levels?
cimetidine, disulfiram, ethanol, isoniazid, and valproic acid (also displaces BDZs from binding sites)
Which drug decreases diazepam excretion?
acetaminophen
Which drugs decrease the absorption of BDZs, thereby decreasing their levels?
antacids
Which drugs increase the metabolism of BDZs?
oral contraceptives
Which BDZs are used to treat insomnia?
triazolam (halcion), temazepam (restoril), and flurazepam
Which BDZ is used to treat only anxiety?
oxazepam
Which BDZ is used to treat only panic disorders?
alprazolam (xanax)
Which BDZ is used for the treatment of anxiety, preanesthetic medication, and status epilepticus?
lorazepam (ativan)
Which BDZ is used for anesthesia and medical procedures?
midazolam (versed)
Which BDZ is used for the treatment of epilepsy and anxiety?
clorazepate
Which BDZ is used for the treatment of anxiety, skeletal muscle relaxation, preanesthetic medication, and status epilepticus?
diazepam (valium)
Which BDZ is used for ethanol withdrawal symptoms, anxiety, and preanesthetic medication?
chlordiazepoxide
On what does the CNS depressant action of barbiturates depend?
their lipid solubility
If a barbiturate has high lipid solubility, how does this affect its pharmacokinetics?
it works faster, has decreased duration of action, increased metabolic degradation, and greater hypnotic effect
How is the action of barbiturates terminated?
physical redistribution to fat tissue, hepatic metabolism, and urinary excretion
Which enzymes do barbiturates induce?
hepatic microsomal enzymes
How do barbiturates work?
they bind to GABAa receptors, increasing the duration of the opening of the chloride channel
What is the longest-acting barbiturate and what is its use?
phenobarbital; it's an anticonvulsant
What are the two ultra-short-acting barbiturates and what is their use?
thiopental and methohexital; induction of anesthesia
Sudden withdrawal of barbiturates after prolonged use may cause what dangerous side effects?
SEIZURES, orthostatic hypotension, cardiovascular collapse
What are the symptoms of barbiturate overdose?
mild OD is like ethanol intoxication; severe OD can cause coma, shock, and hypothermia
What are some side effects of barbiturates? (hint: there are a LOT; no one should take these!!)
sedation, ataxia, respiratory depression, rash, angioedema, folate-responsive megaloblastic anemia, osteomalacia, acute intermittent porphyria
When barbiturates induce microsomal enzymes, they increase the metabolism of what other drugs?
phenytoin, steroid hormones, tricyclic antidepressants, oral anticoagulants, digoxin, quinidine, theophylline, and beta-blockers
How does buspirone work?
it's a partial agonist at 5HT1a receptors; it decreases serotonin
What is different about the effects buspirone when compared to BDZs?
buspirone has no muscle relaxant or anticonvulsant activity and doesn't increase the CNS depressant effect of ethanol
How does zolpidem tartrate work?
It is a GABAa agonist (?)
it's BZ1 selective as opposed to BDZs, which interact with BZ1 and BZ2
What is buspirone used for? Zolpidem tartrate?
anxiety; short-term treatment of insomnia
What is meprobamate used for?
anxiety and sedation
What is chloral hydrate used for?
sleep inducer
What are the side effects of chloral hydrate?
irritation of mucous membranes and inhibition of ethanol metabolism
What is glutethimide used for?
sedation/hypnotic
What are the side effects of glutethimide?
anticholinergic effects
Which drugs induce hepatic microsomal enzymes?
barbiturates, meprobamate, glutethimide
Phenobarbital has been used to treat what neonatal illness? Why?
kernicterus and hyperbilirubinemia; it increases the elimination of bilirubin

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