Pharmacology - Antiepileptic Drugs Flashcards Preview

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Flashcards in Pharmacology - Antiepileptic Drugs Deck (38):
1

What are the molecular targets and actions of antiepileptic drugs?

1. To limit excitability - voltage-gated Na and Ca channels and glutamate receptors
2. To enhance inhibition of GABA system

2

Phenytoin
Carbamazepine
Oxcarbamazepine
Lamotrigine

These drugs all do what?

Antiepileptics and voltage-gated Na channels

Goal to stabilize the inactive state inhibiting recurrent depolarization

3

Blocking what channels decreases neuropathic pain?

Calcium channels

Ie Ethosuximide - T-type in thalamus

Gabapentin, Pregabalin - the high voltage type

4

Give the class: Felbamate

Glutamate receptor blocker

NMDA receptor blocker; secondary effect at voltage-gated Na and Ca channels, GABA system

5

Give the class: Topiramate

Glutamate receptor blocker

Partial AMPA, Kainate Ca receptor blocker; secondary effect at voltage-gated Na channel, GABA system

6

Phenobarbitol and benzodiazepines activate what system in treating epilepsy?

GABA system

7

Give the class: Carbamazepine

Sodium channel blocker

MOA: Stabilize inactive conformation of Na channel

AEs: Dizzy, drunk, double vision, mild myelosuppression

8

Give the indications for Carbamazepine.

Better for complex partial epilepsy than primary generalized seizures

9

In addition to epilepsy, carbamazepine is also useful in treating:

Bipolar Affective disorder (also neuropathic pain)

More effective for complex partial seizure than primary generalized; bipolar disorder; neuropathic pain

10

What is the most important thing to remember about carbamazepine?

Autoinduction - it can induce metabolism of itself (requires dose increase after reaching steady state)

Heteroinduction - it can induce metabolism of other drugs
for example: contraceptive pill failure

11

Give the side effects: carbamazepine

Rash (rarely, Stevens-Johnson), mild myelosuppression, mild increase in LFTs; can cause contraceptive failure

12

Give the class: Phenytoin

Voltage-gated Na channel stabilizer

13

Give the MOA: Phenytoin

Stabilize inactive conformation of Na channel

14

Give the indications: Phenytoin

Effective for tonic-clonic seizures of primary generalized epilepsy or partial onset and secondary generalized seizures

Less effective for absence (particular pediatric), myoclonic, atonic seizures

15

Give the side effects: Phenytoin

Long term side effects?

Rash, gingival hyperplasia, hirsutism, lupus-like reaction; can cause contraceptive failure

Long term: Cerebellar degeneration, peripheral neuropathy, osteoporosis

16

IV-Phenytoin is useful to treat what condition?

Status epilepticus

same with IV Valproate

17

How is oxcarbazepine different from carbamazepine?

Oxcarbazepine is less protein-bound, less autoinduction, fewer interactions, less toxic, has a longer half-life than carbamazepine

18

TEST QUESTION:
Lamotrigine is associated with what toxicity?

Dizziness
Sedation
Ataxia
Diplpia

AEs: rash (rarely Stevens-Johnson syndrome), slow initial titration is important

19

Is Lamotrigine indicated for use in children to treat epilepsy?

Yes
Effective for primary generalized epilepsy, partial complex epilepsy and secondary generalization, absence

20

Lamotrigine is NOT effective for what kind of seizures?

Myoclonic seizures

May exacerbate myoclonic seizures; competes with valproic acid for excretion (potential synergy); hepatic enzyme inducer; not very protein bound

21

Give the indications for Lamotrigine.

Primary generalized epilepsies, absence seizures; indicated in children; bipolar disorder; neuropathic pain

22

Lamotrigine has synergistic action with what drug?

Depakote (valproic acid)

23

T/F: Lamotrigine can cause contraceptive failure.

True
Same with ALL voltage-gated sodium channel blockers - Phenytoin, Carbamazepine, Oxcarbamazepine

24

Give the class: Gabapentin and Pregabalin

GABA analog

25

Give the MOA of Gabapentin and Pregabalin.

Block presynaptic influx of Ca

26

Give the indications for Gabapentin and Pregabalin.

Adjunct for partial complex epilepsy; more commonly used for neuropathic pain

27

Ethosuximide is only effective against what kind of seizure?

Absence seizures

28

Give the side effects: Ethosuximide

Nausea (transient)
Sedation
Irritability

29

What is the half life of ethosuximide?

40-60 hours

30

T/F: Topiramate is active at the postsynaptic membrane.

True

Partial AMPA, Kainate Ca receptor blocker; secondary effect at voltage-gated Na channel, GABA system

Use: Partial onset seizures, secondary generalized seizures, primary generalized epilepsy; migraine prevention, long-term prevention of cluster headaches

Side Effects: Mild metabolic acidosis, kidney stones (due to some carbonic anhydrase activity); modest weight loss; rare acute glaucoma; sedation and **word finding difficulties**

-Respiratory compensation from acidosis results in mild alkylosis, calcium ionization, and a sensation of tingling in fingers that can be alleviated with vitamin C

31

What drug is a good choice to treat partial onset and secondarily generalized seizures?

Levetiracetam

32

Give the class: Levetiracetam

Synaptic vesicle binder

Binds to vesicle protein 2 resulting in less neurotransmitter release

33

Give the side effects: Levetiracetam

Irritability
Aphasia
Thrombocytopenia

Toxicity: Sedation

34

What is the MOA for Ethosuximide?

Blocks T-type calcium channels in thalamus

35

What is a common cause of temporal lobe epilepsy?

Head trauma

36

What is the difference in molecular targets between Felbamate and Topiramate?

Felbamate = NMDA antagonist
Topiramate = partial AMPA/Kinate antagonist

37

Difference between side effect and toxicity?

Side effect is a drug effect that is not related to drug's intended mechanism of action (e.g. developing a rash from taking a sodium channel blocker - Carbamazepine) whereas toxicity is an undesirable effect that is related to the mechanism of action (e.g. sedation, ataxia, diplopia from sodium channel blocking anti-epileptic - Carbamazepine)

38

What causes carbamazepine toxicity (drunk, dizzy, double vision)?

epoxide metabolite

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