Anticonvulsants

Question 1

What is the main drug used for absence seizures?

Answer 1

ethosuximide but valproic acid can be used as well

Question 2

What drug do you need to remember is good for the treatment of status epilepticus?

Answer 2

IV benzodiazepines

Question 3

MOA phenytoin?

Answer 3

Decreased axonal conduction by preventing Na+ influx through fast Na channels

Question 4

MOA of felbamate?

Answer 4

NMDA receptor blocker

Question 5

MOA of ethosuximide?

Answer 5

Decreased presynaptic Ca2+ influx. through type T channels in thalamic neurons

Question 6

MOA of lamotrigine?

Answer 6

AMPA receptor blocker and Na+ channels

Question 7

MOA of topiramate?

Answer 7

AMPA receptor blocker (glutamate receptors)

Blocks Na+ channels

enhances GABA activity

Question 8

MOA of carbamazepine?

Answer 8

Decreased axonal conduction by preventing Na+ influx through fast Na channels

Question 9

MOA of valproic acid

Answer 9

• Decreased presynaptic Ca2+ influx. through type T channels in thalamic neurons (blocks T-type Ca2+ channels)
• inhibition of GABA transaminase
• blocks voltage gated Na+ channels in their inactivated state

Question 10

What are the S/Es of phenytoin/contraindications?

Answer 10

CNS depression
gingival hyperplasia
hirsutism
osteomalacia (dec vit. D)
megaloblastic anemia ( dec folate)
aplastic anemia (check hematology lab results)

contraindications:
pregnancy (teratogen)

Question 11

What teratogenic effect does phenytoin produce in the fetus?

Answer 11

cleft lip and palate

Question 12

Uses for carbamazepine?

Answer 12

seizures
DOC for trigeminal neuralgia
BPD

Question 13

S/E of carbamazepine? Contraindications?

Answer 13

CNS depression
osteomalacia
megaloblastic anemia
aplastic anemia
exfoliative dermatitis
inc. ADH secretion (dilution hyponatremia)

Contraindications:
pregnancy (teratogen)

Question 14

What teratogenic effect does carbamazepine produce in the fetus?

Answer 14

cleft lip and palate; spina bifida

Question 15

What are the uses of valproic acid?

Answer 15

seizures
BPD
migraine prophylaxis

Question 16

What affect does valproic acid have the cytochrome P450?

Answer 16

inhibits cytochrome P450

Question 17

What is the S/E profile of valproic acid? Contraindicaitons?

Answer 17

hepatotoxicity (from toxic metabolite)
thrombocytopenia
pancreatitis
alopecia

VALPROATE

Vomiting
Alopecia
Liver Toxicity
Pancreatitis/Pancytopenia
Retain fat
Oedema
Appetite increase
Tremor
Enzyme Inhibitor

Contraindications:
Pregancy (teratogen)

Question 18

What is the teratogenic effect associated with using valproic acid?

Answer 18

spina bifida

Question 19

S/E profile of lamotrigine?

Answer 19

SJS

Question 20

S/E of topiramate?

Answer 20

weight loss

Question 21

S/E of felbamate

Answer 21

aplastic anemia

Question 22

MOA gabapentin.

Answer 22

inhibit the action of α2δ-1 subunits, thus decreasing the density of pre-synaptic voltage-gated calcium channels and subsequent release of excitatory neurotransmitters

basically affects calcium channels and neurotransmitter release leading to GABA effects

Question 23

Gabapentin uses.

Answer 23

seizures and neuropathic pain (such as postherpetic neuralgia)

Question 24

How may many anticonvulsants reduce the efficacy of OC’s?

Answer 24

Oral contraceptives are P450 substrates and many anticonvulsants are P450 inducers