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37 Cards in this Set
- Front
- Back
Describe the dose dependent progression of depressant effects seen with barbiturates.
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From low dose to high dose:
1) anti-anxiety 2) sedation 3) hypnosis/sleep 4) coma 5) anesthesia 6) death |
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What is the major advantage of benzodiazepines over the older sedative/hypnotic drugs?
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Benzodiazepines do not depress respiration (unless other CNS depressants are taken concomitantly...then all bets are off).
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Describe barbiturate mechanism of action at low/therapeutic doses.
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-bind to GABA-A receptor in allosteric location
-potentiate action of GABA by prolonging chloride channel opening |
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Describe barbiturate mechanism of action at high/toxic doses.
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-barbiturates directly stimulate the GABA-A receptor at high doses
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Describe the classification of barbiturates.
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(1) ultra short acting: half life 15-20min; example: thiopental
(2) short-intermediate acting: half life 3-6h; examples: pentobarbital, secobarbital, amobarbital (3) long-acting: half life >6h; example: phenobarbital |
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Describe barbiturate effects on CNS.
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-can induce all levels of depression
-low therapeutic index -can increase reaction to pain -tolerance to mood/hypnotic effects occurs more quickly than to lethal effects -barbiturates are used to induce anesthesia and to manage seizure disorders |
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Describe barbiturate effects on PNS.
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-depress autonomic ganglia (may be responsible for the initial hypotension that occurs after barbiturate administration)
-depress cholinergic transmission at NMJ (paralytic effects of curare are enhanced during barbiturate anesthesia) |
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Describe barbiturate effects on respiration at:
(1) hypnotic dose (2) 3X dose (3) 10X dose |
(1) hypnotic dose: neurogenic drive is reduced
(2) 3X dose: neurogenic drive is gone; hypoxic and chemoreceptor drives are reduced (3) 10X: all drives fail |
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Describe barbiturate effects on cardiovascular system.
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-at anesthetic doses, may cause hypotension in patients with CHF
-at suicidal/toxic doses, causes depression of cardiac conduction |
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Describe barbiturate effects on liver.
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-induce P450 enzymes
-contraindicated in porphyria |
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Describe paradoxical excitement with the use of barbiturates.
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Paradoxical excitement is a toxicity effect. The patient, often an elderly person or a debilitated person, will show signs of inebriation.
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Phenobarbital can cause this rare hypersensitivity reaction.
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fatal toxic epidermolysis bullosum
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Barbiturates enhance the metabolism of many drugs, such as....
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(1) vitamin D and K
(2) anticoagulants (3) steroids (ex: birth control pills) (4) methylphenidate (5) antihistamines |
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Describe the CNS therapeutic uses of barbiturates.
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-induce anesthesia (thiopental)
-management of acute seizure disorders (phenobarbital) -treatment of sustained seizures due to tetanus, eclampsia or convulsant poisoning -therapeutic coma during neurosurgery or after a head injury |
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What class of CNS depressants would be used to induce metabolism of hyperbilirubinemia in neonates?
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barbiturates
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What non-barbiturate drug could you administer to a child prior to taking him to get an MRI?
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chloral hydrate -- used to induce sedation in children
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You discover that your patient has gastric bezoars. You should probably ask him if he has a history of taking this non-barbiturate drug.
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meprobamate
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Describe benzodiazepine mechanism of action.
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-binds to GABA-A receptor
-enhances GABA mediated chloride influx by increasing the frequency of gating events -benzodiazepines do NOT directly activate the GABA receptor...ever...not even at high doses |
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TRUE OR FALSE
Barbiturates can activate the GABA receptor while benzodiazepines cannot. |
TRUE
Barbiturates activate the GABA receptor at high/toxic doses. |
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Describe the classification of benzodiazepines.
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(1) short acting: half life <6h; examples: triazolam, midazolam
(2) intermediate acting: half life between 6 & 24h; example: temazepam (3) long acting: half life >24h; examples: diazepam, flurazepam, chlordiazepoxide |
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Describe benzodiazepine effects on the CNS.
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-CNS depression up to coma but do not induce respiratory depression
-preanesthetics |
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Describe benzodiazepine effects on respiration.
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-no effect on respiration at hypnotic doses
-can suppress hypoxic drive at anesthetic doses which can lead to respiratory acidosis in COPD patients |
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While benzodiazepines are relatively safe drugs, describe some of their toxic effects.
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-ataxia
-confusion, amnesia -dependence & abuse -overdose with benzodiazepine alone is rarely fatal |
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Name the novel benzodiazepine receptor agonists.
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1. zaleplon
2. zolpidem 3. eszopiclone These are hypnotic agents with low tolerance and dependence. |
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Name the benzodiazepine receptor antagonist.
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flumazenil
-has rapid onset & short duration of action -reverses sedative effects of benzodiazepines in anesthesia or overdose situations |
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Describe the use of benzodiazepines in the treatment of acute anxiety (namely diazepam).
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Benzodiazepines are useful as premedication for anxious or apprehensive patient.
Diazepam is very useful because of its rapid onset & muscle relaxant effects. |
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Describe the use of benzodiazepines in the treatment of chronic anxiety.
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Benzodiazepines are used in conjunction with psychotherapy for limited periods of time
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This adrenergic antagonist could be beneficial to a patient with stage fright.
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propranolol
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This antihistamine could be beneficial to a patient with anxiety.
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hydroxyzine (causes sedation)
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Why are benzodiazepines better than barbiturates in the treatment of insomnia?
Furthermore, why do benzodiazepine receptor agonists have an advantage over benzodiazepines? |
Barbiturates induce sleep, which resembles physiological sleep but they can disrupt normal sleep cycles. They reduce the amount of time spent in REM sleep.
Benzodiazepines are less likely to alter the sleep pattern compared to barbiturates. Zolpidem & zaleplon -- non-barbiturate hypnotic agents -- have less residual mental impairment and less abuse potential compared to benzodiazepines. |
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This class of barbiturates has been used to produce daytime sedation in severe anxiety attacks.
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long-acting barbiturates (phenobarbital)
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This class of barbiturates has been used as adjuncts in HTN treatment.
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short-intermediate barbiturates (pento-, seco-, amo- barbital)
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Which short acting benzodiazepine has replaced diazepam for use as a preanesthetic?
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Midazolam has replaced diazepam because it has better amnesia effects.
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Which barbiturate and which benzodiazepine are used to treat epilepsy?
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phenobarbital (long acting barb)
diazepam (long acting benzo) |
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Which barbiturate and which benzodiazepene were listed as agents that induce anesthesia (pg. 286).
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1) thiopental (ultrashort barb)
2) midazolam (short benzo) |
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Because barbiturates induce hepatic P450 enzymes, barbiturates are contraindicated in patients with...
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porphyria
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TRUE or FALSE
Barbiturates have a low therapeutic index while benzodiazepines have a high therapeutic index. |
TRUE
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