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Pharmacology > 25 Antiepileptic drugs > Flashcards

25 Antiepileptic drugs Flashcards

1
Q

25.01 SODIUM CHANNEL INHIBITORS

Carbamazepine, oxcarbazepine, phenytoin - actions

A

anticonvulsant
relieves neuropathic pain

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2
Q

25.01 SODIUM CHANNEL INHIBITORS

Carbamazepine, oxcarbazepine, phenytoin - MOA

A

blocks Na+ channels to inhibit action potential initiation and propagation
use-dependence of block means that action is preferentially on rapidly firing neurons in the epileptic focus

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3
Q

25.01 SODIUM CHANNEL INHIBITORS

Carbamazepine, oxcarbazepine, phenytoin - abs/distrib/elim

A

these drugs are metabolised by P450 and are potent enzyme inducers, thus associated with many serious drug interactions
phenytoin half-life 20h, but increases with dose due to saturation kinetics
monitoring of plasma concentrations required due to narrow therapeutic range

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4
Q

25.01 SODIUM CHANNEL INHIBITORS

Carbamazepine, oxcarbazepine, phenytoin - clinical use

A

partial and generalised (tonic-clonic) seizures
also neuropathic pain and bipolar disorder
phenytoin use is decreasing due to poor pharmacokinetic and toxicity profile, although still used in status epilepticus

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5
Q

25.01 SODIUM CHANNEL INHIBITORS

Carbamazepine, oxcarbazepine, phenytoin - adverse effects

A

drowsiness, dizziness, ataxia, mental disorientation
rare, but serious skin reactions with carbamazepine
phenytoin may cause thickening of the gums and hirsutism

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6
Q

25.02 T-TYPE CALCIUM CHANNEL BLOCKERS

Ethosuximide - actions

A

anticonvulsant with specific action on absence seizures

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7
Q

25.02 T-TYPE CALCIUM CHANNEL BLOCKERS

Ethosuximide - MOA

A

blocks T-type Ca2+ channels in thalamic neurons to counteract the slow (3 Hz), spike-and-wave firing pattern thought to be important in absence epilepsy

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8
Q

25.02 T-TYPE CALCIUM CHANNEL BLOCKERS

Ethosuximide - abs/distrib/elim

A

given orally
oxidised by cytochrome P450 system
half-life 60h

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9
Q

25.02 T-TYPE CALCIUM CHANNEL BLOCKERS

Ethosuximide - clinical use

A

drug of choice for absence seizures (not effective against partial or tonic-clonic seizures)

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10
Q

25.02 T-TYPE CALCIUM CHANNEL BLOCKERS

Ethosuximide - adverse effects

A

anorexia, GIT upset, pancytopaenia
rash, drowsiness, fatigue
overdose can cause coma and respiratory depression

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11
Q

25.03 BROAD-SPECTRUM ANTIEPILEPTIC

Valproate - actions

A

anticonvulsant
mood stabiliser

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12
Q

25.03 BROAD-SPECTRUM ANTIEPILEPTIC

Valproate - MOA

A

several actions may contribute to the antiepileptic action
blocks voltage-gated Na+ channels to inhibit action potential initiation and propagation
inhibits GABA transaminase to reduce GABA breakdown
may also affect T-type calcium channels

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13
Q

25.03 BROAD-SPECTRUM ANTIEPILEPTIC

Valproate - abs/distrib/elim

A

given orally
subject to glucuronidation and mitochondrial oxidation
half-life 9-16h

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14
Q

25.03 BROAD-SPECTRUM ANTIEPILEPTIC

Valproate - clinical use

A

broad coverage of most forms of epilepsy, but appears particularly useful in generalised seizures and absence seizures
manic phase of bipolar disorder
migraine
contraindicated in women of reproductive age due to risk of teratogenicity

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15
Q

25.03 BROAD-SPECTRUM ANTIEPILEPTIC

Valproate - adverse effects

A

nausea and vomiting
tremor
weight gain
reproductive dysfunction
hepatotoxicity
teratogenic effects (e.g. neural tube defects, including spina bifida)

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16
Q

25.04 BENZODIAZEPINES

Lorazepam, midazolam, diazepam, clonazepam, clobazam - actions

A

anticonvulsant
also hypnotic and anxiolytic

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17
Q

25.04 BENZODIAZEPINES

Lorazepam, midazolam, diazepam, clonazepam, clobazam - MOA

A

bind to benzodiazepine binding site on GABAA receptor to enhance channel opening by GABA
increased Cl− permeability reduces electrical excitability
clonazepam and clobazam are said to be more selective anticonvulsants with less sedation

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18
Q

25.04 BENZODIAZEPINES

Lorazepam, midazolam, diazepam, clonazepam, clobazam - abs/distrib/elim

A

given orally for chronic use (IV for status epilepticus)
if no IV access, IM/buccal midazolam or rectal diazepam
metabolised by P450 system and glucuronide conjugation

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19
Q

25.04 BENZODIAZEPINES

Lorazepam, midazolam, diazepam, clonazepam, clobazam - clinical use

A

lorazepam, diazepam or clonazepam can be given IV for status epilepticus
oral clonazepam is used for tonic-clonic and absence seizures
clobazam is used as an add-on anticonvulsant to existing therapy

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20
Q

25.04 BENZODIAZEPINES

Lorazepam, midazolam, diazepam, clonazepam, clobazam - adverse effects

A

unwanted effect in treating epilepsy is sedation
severe respiratory depression when used IV or in combination with other CNS depressants (e.g. ethanol)

21
Q

25.05 BARBITURATES

Phenobarbital - actions

A

anticonvulsant
hypnotic (at higher doses)

22
Q

25.05 BARBITURATES

Phenobarbital - MOA

A

binds to barbiturate binding site on GABAA receptor to enhance Cl− channel opening by GABA
this reduces neuronal excitability and action potential frequency at the epileptic focus
effects on Na+ and Ca2+ channels may contribute to the anticonvulsant activity

23
Q

25.05 BARBITURATES

Phenobarbital - abs/distrib/elim

A

given orally
some drug is excreted unchanged, but the majority is oxidised in the liver
half-life 50-100h

24
Q

25.05 BARBITURATES

Phenobarbital - clinical use

A

tonic-clonic and simple partial seizures, but less frequently used in clinical practice nowadays due to toxicity and unfavourable pharmacokinetics related to liver enzyme induction

25
Q

25.05 BARBITURATES

Phenobarbital - adverse effects

A

highly sedative
megaloblastic anaemia, hypersensitivity reactions
in overdose - coma, respiratory and circulatory failure
induces dependence

26
Q

25.06 BROAD-SPECTRUM ANTIEPILEPTIC

Gabapentin (similar: pregabalin) - actions

A

anticonvulsant, analgesic, anxiolytic

27
Q

25.06 BROAD-SPECTRUM ANTIEPILEPTIC

Gabapentin (similar: pregabalin) - MOA

A

action is attributed to binding to the α2-δ-1 and α2-δ-2 subunits of voltage-activated Ca2+ channels (P/Q or N-type) to block Ca2+ entry and exocytosis of transmitter (glutamate) from nerve endings
(enhanced release of GABA has also been suggested)

28
Q

25.06 BROAD-SPECTRUM ANTIEPILEPTIC

Gabapentin (similar: pregabalin) - abs/distrib/elim

A

given orally
excreted unchanged
half-life 6h (longer with renal impairment)

29
Q

25.06 BROAD-SPECTRUM ANTIEPILEPTIC

Gabapentin (similar: pregabalin) - clinical use

A

adjunctive treatment for partial seizures
widely used to treat neuro­pathic pain
anxiolytic used in generalised anxiety disorders

30
Q

25.06 BROAD-SPECTRUM ANTIEPILEPTIC

Gabapentin (similar: pregabalin) - adverse effects

A

sedation, dizziness and unsteadiness
both gabapentin and pregabalin have become drugs of abuse because they potentiate the effects of opioids

31
Q

25.07 BROAD-SPECTRUM ANTIEPILEPTIC

Lamotrigine - actions

A

anticonvulsant
reduces frequency of mood episodes in bipolar disorder

32
Q

25.07 BROAD-SPECTRUM ANTIEPILEPTIC

Lamotrigine - MOA

A

inhibition of glutamate release decreases postsynaptic neuronal excitation
this may be due to Na+ (and perhaps Ca2+) channel inhibition in the nerve ending

33
Q

25.07 BROAD-SPECTRUM ANTIEPILEPTIC

Lamotrigine - abs/distrib/elim

A

oral administration
subject to hepatic glucuronidation
half-life 24-36h

34
Q

25.07 BROAD-SPECTRUM ANTIEPILEPTIC

Lamotrigine - clinical use

A

broad-spectrum anticonvulsant, covering partial and generalised seizures, including absence
bipolar disorder

35
Q

25.07 BROAD-SPECTRUM ANTIEPILEPTIC

Lamotrigine - adverse effects

A

dizziness, headache, double vision, sedation
serious skin rashes may occur in a small percentage of patients, particularly children

36
Q

25.08 AMPA RECEPTOR BLOCKERS

Topiramate (similar: perampanel) - actions

A

anticonvulsant

37
Q

25.08 AMPA RECEPTOR BLOCKERS

Topiramate (similar: perampanel) - MOA

A

topiramate most likely blocks AMPA/kainate receptors for glutamate, but also blocks voltage-dependent Na+ channels and potentiates GABA action on GABAA receptors
perampanel is a non-competitive blocker of the AMPA receptor on postsynaptic neurons

38
Q

25.08 AMPA RECEPTOR BLOCKERS

Topiramate (similar: perampanel) - abs/distrib/elim

A

given orally

39
Q

25.08 AMPA RECEPTOR BLOCKERS

Topiramate (similar: perampanel) - clinical use

A

generalised tonic-clonic and partial seizures (usually as adjuncts)
also used for migraine prophylaxis

40
Q

25.08 AMPA RECEPTOR BLOCKERS

Topiramate (similar: perampanel) - adverse effects

A

psychomotor slowing, motor incoordination, memory impairment, paraesthesia, sedation, fatigue, confusion
visual disturbances

41
Q

25.09 BROAD-SPECTRUM ANTIEPILEPTIC

Levetiracetam (similar: brivaracetam) - actions

A

anticonvulsant

42
Q

25.09 BROAD-SPECTRUM ANTIEPILEPTIC

Levetiracetam (similar: brivaracetam) - MOA

A

activity is thought to be due to binding to synaptic vesicle protein SV2A - how this modifies the release of neurotransmitter (e.g. glutamate) is not established

43
Q

25.09 BROAD-SPECTRUM ANTIEPILEPTIC

Levetiracetam (similar: brivaracetam) - abs/distrib/elim

A

given orally or IV
mostly excreted unchanged
half-life 7h

44
Q

25.09 BROAD-SPECTRUM ANTIEPILEPTIC

Levetiracetam (similar: brivaracetam) - clinical use

A

broad-spectrum anticonvulsant
monotherapy for partial seizures in newly diagnosed epilepsy
as an adjunct to other anticonvulsants in the treatment of partial, generalised or myoclonic seizures

45
Q

25.09 BROAD-SPECTRUM ANTIEPILEPTIC

Levetiracetam (similar: brivaracetam) - adverse effects

A

dizziness, headache, fatigue, sedation
few drug interactions

46
Q

25.10 OTHER ANTIEPILEPTIC AND ANTI-SPASTICITY DRUGS

Vigabatrin

A

irreversible inhibition of GABA transaminase in GABAergic nerves increases the GABA concentration
restricted clinical use because vigabatrin causes visual field defects

47
Q

25.10 OTHER ANTIEPILEPTIC AND ANTI-SPASTICITY DRUGS

Tiagabine

A

inhibits the reuptake of GABA (by GAT-1) into GABAergic nerve endings and glia, thus raising synaptic GABA concentration and inhibiting neuronal activity
adjunct use in partial seizures

48
Q

25.10 OTHER ANTIEPILEPTIC AND ANTI-SPASTICITY DRUGS

Zonisamide, lacosamide

A

act on Na+ channels
mainly used in partial seizures

49
Q

25.10 OTHER ANTIEPILEPTIC AND ANTI-SPASTICITY DRUGS

Baclofen

A

selective agonist at GABA receptor
acts mainly on spinal cord for muscle spasticity from multiple sclerosis or spine trauma
not used in epilepsy

Pharmacology (34 decks)

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