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Pharmacology 2 > 2.3 barbiturates > Flashcards

2.3 barbiturates Flashcards

1
Q

barbiturates

A

derivatives of barbituric acid
(condensed product of malonic acid and urea)

– replaced by benzos for sedative action

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2
Q

thiobarbiturates

A

barbiturates in which oxygen is replaced by sulphur
–more lipid soluble,
shortened duration of action,
increased hypnotic potency

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3
Q

barbiturates as a CNS depressant

A

barbiturates increase the duration of the GABA mediated chloride channel openings at multiple sites in the CNS and prolong GABA activity

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4
Q

barbiturates at high concentration

A

barbiturates may also be gabamimetic,
directly activating chloride channels

– can act at GABA -A receptors without GABA

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5
Q

barbs bind

A

to another side on the gaba chloride channel to exert the gaba-facilitatory action

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6
Q

barbs also inhibit

A

complex 1 of ETC and hence no ATP synthesis in neurons
(itself CNS depressant action)
(very different form bzd)

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7
Q

barbs increase

A

duration of opening not frequency like benzos

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8
Q

AMPA (glutamate) receptors

A

also blocked by barbiturates

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9
Q

high dose barbs can block

A

Na channel

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10
Q

ultrashort barb

A

20 min – thiopental

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11
Q

short acting barb

A

3-10hrs –

Pento barbital,
seco barbital,
amo barbital

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12
Q

long acting

A

1-2 days– phenobarbital

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13
Q

barbs on cns

A

produce dose dependent effects:

sedation–>sleep/hypnosis –>anesthesia–> coma

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14
Q

barbs reversibly depress

A

activity of all excitable tissues

–> mild sedation to general anesthesia to coma

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15
Q

TI of barbs

A

low

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16
Q

barbs and pain

A

increase the reaction to painful stimuli (hyperanlgesic action) hence not relied to produce sedation in pain

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17
Q

barbs and sleep

A 
in low dose can produce drowsiness, 
reduction in excitability (sedative actions), 
dec sleep latency, 
inc total duration of sleep (inc st2), 
dec REM and SWS (St 3 and 4), 
dec night awakenings
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18
Q

effect of REM-NREM disruption

A

the subject may feel confused and unsteady if wakened early –
hangover (dizziness, distortions of mood, irritability and lethargy)
may occur in the morning after a night dose.

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19
Q

tolerance to sleep effect of barbs

A

tolerance to the effects on sleep occur w/in a few days –total sleep time may be reduced as much as 50% after 2 w/ of use

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20
Q

barb for anticonvulsant

A

phenobarbital

  • -high-anticonvulsant:sedative ratio
    • it has specific anticonvulsant action independent of general CNS depression
  • -ok during prg
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21
Q

barb for respiration

A

depress respiration in higher doses
– neurologic, hypercapnic (chemoreceptor) and hypoxic drives to respiratory centres are depressed in succession,
overdosage causes severe reps depression and death

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22
Q

barb on CVS hypnotic dose

A

light dec in BP and HR (same as during sleep)

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23
Q

barb on CVS toxic dose

A

marked fall in BP (due to ganglionic blockade, vasomotor center depression and direct decrease in cardiac contracility)

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24
Q

barb on skeltal musl

A

anesthetic dose decreases muslce contraction by deressing transmission in autonomic ganglia

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25
Q

barb on liver

A

induce cyp450 thus increases metabolism of many lipid soluble drugs and vitamins D/K,

induce the enzyme glucuronyl transferase,

increase ALA synthetase – dangerous exacerbationof prophyria

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26
Q

barb on kidney

A

dec urine flow (due to decreased BP and increased ADH release),
severe oliguria/anuria in acute barbiturate poisoning
(due to marked hypotension)

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27
Q

barb on GIT

A

dec the tone and rhythmic contractions

28
Q

barb pharmacokinetics

A

orally well absorbed,
distributed widely and cross placenta,
oxidation is the important biotransformation reaction,
duration of the action is dependent on the redistribution

29
Q

theraputic uses of barbs is very limited bc of

A

lack of specificty of effect in the CNS,
lower TI than bzds,
tolerance occurs more rapidly than bzds,
liability for abuse is great,
considerabul drug interactions

30
Q

barbs as anticonvulsant

A 
phenobarbital --used in 
tonic-clonic seizures, 
status epilepticus, 
eclampsia, 
tetanus, 
poisoning by convulsant drugs
31
Q

barbs as anesthetics

A

thiopental, methohexital – ultrashort acting admin by IV

32
Q

barbs in hyperbilirubinemia, congenital non-hemolytic jaundice and kernicterus

A

phenobarbital

33
Q

barbs in psych

A

thiopental sodium, amobarbital –

diagnosis and treatment of narcoanalysis and carcotherapy

34
Q

barb on anti-anxiety and hypnotic

A

pentobarbital – however not used noadays

35
Q

barbiturates adverse effects

A

hangover effect,
impairment of finemotor skills,
idiosyncrasy (paradoxical excitement in geriatric and debilitated pts),
behavioural disturbances after long term treatment,
hypersensitivity,
drug automation,
tolerance (both PK and PD) and dependance
(physical and psychological)

36
Q

barb drug interactiosn w/ other CNS depressants

A

additive response with another CNS depressants (possible life-thratening respiratory depression) such as
anesthetics,
antihistamines,
opiates

37
Q

barbs induce metabolism of

A 
most lipid soluble drugs such as 
oral contraceptives, 
warfarin, 
carbamezepine, 
phenytoin, etc

and also increases the metabolism of vit K/D

38
Q

barbs and calcium

A

dec calcium abs leading to coagulation defects

39
Q

barbs and porphyrin syn

A

inc porphyrin synthesis and hence contraindi

40
Q

chronic use of barbs leads to

A

tolerance

41
Q

cross tolerance occurs btw

A

benzos,
barbiturates, and
ethanol

42
Q

barbs vs benzos

A

greater abuse liability than benzos

43
Q

withdrawal of barbs

A

abrubt withdrawal leads to the same symptosm as benzos but more intense nature, life threatening seizures can occur

44
Q

acute barbiturate poisoning

A

respiratory depression,

marked hypotention

45
Q

barb management

A

maintanance of ABC,
gastric lavage,
force alkaline diuresis (mannitol and NaHCO3),
hemodialysis

46
Q

contraindications of barbs

A

kidney and liver disorders,
acute intermittent porphyria,
severe pulmonary insufficiency (asthma, COPD, Emphysema),
obstructive Sleep apnea (OSA)

47
Q

novel benzodiazepine receptor agonists

A 
zolpidem, 
zaleplon, 
eszopiclone, 
sopiclone 
 -- they do not have anticonvulsant and muscle relaxant properties
48
Q

zolpidem

A

non-benzodiazepine,
acts on a subset of bzd receptors (bz1),
less tolerance abuse liability,
used in sleep disorders
(esp to shorten sleep-latency and prolong total sleep time),
no muscle relaxation and anti-convulsant action,
duration of action 6-8hrs,
overdose reversed by flumazenil

49
Q

zaleplon acts on

A

bz1

50
Q

one of the best choices for inducing sleep

A

zaleplon

51
Q

plasmal level of zaleplon

A

increases when combined with cimetidien and

decreases when given with rifampin

52
Q

ezopiclone

A

rapid onset, effective in sleep-onset insomnia and also reduces number of awakenings and increases total sleep time and sleep quality

53
Q

ezopiclone duration of action

A

6 hrs

54
Q

ezopiclone overdoes can be reversed by

A

flumazenil

55
Q

drug for long term use up to 6 monts

A

eszopiclone

56
Q

buspirone

A

5HT1a partial agonist
– at the presynaptic receptors by interfering with the firing of 5HT neurons,
no effect on GABA,
relieves anxiety without producing marked sedative hypnotic effects

57
Q

how buspirone works

A

initially binding decreases release of 5HT creating anxiety

BUT the receptors get desensitized and then release 5HT reducing anxiety

58
Q

buspirone used for

A

generalized anxiety disorder and chronic anxiety
– effects seen after 1-2 weeks
(unsuitable for management of acute anxiety state)

59
Q

buspirone dependence liability

A

none

60
Q

buspirone impairment of psychomotor skills

A

less impairment than bzds and does not affect driving skills

61
Q

buspirone abs

A

orrally effective and undergoes extensive first pass metabolism

62
Q

buspirone does not

A

do muscle relaxaiton or anticonvulsant activity,

no rebound-anxiety or withdrawla signs on abrupt discontinuation

63
Q

histamine H1

A

invovled in wakefulness

64
Q

H1 antagonists

A

diphenhydramine,
doxylamine,
hydroxyzinej

65
Q

other sleep promoting drugs

A

choral hydrate/trichlorofos,
melatonin (jet lag),
ramelteon (melatonin agonsit)
valerian (herbal sleep rememdy)

Pharmacology 2 (12 decks)

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