MCQ's: Drugs used In Epilepsy

Question 1

Sodium valproate:

Mode of action?

Answer 1

• weakly blocks sodium ion channels.

- inhibits GABA transaminase, which would deactivate GABA and may also stimulate GABA synthesis.

Question 2

Sodium valproate:

1. Contra-indicated in children?
2. Used to treat what type of seizures?
3. Effect in GABA concentrations?

Answer 2

1. Safe use in children down to 1 month age.
2. Treats petit mal, generalised, mixed and partial seizures.
3. Enhances concentrations of GABA.

Question 3

Valproic acid:

1. Metabolism?
2. Form at room temperature?
3. Effect on platelet?
4. Effective for how long post Tx?

Answer 3

1. 75% metabolised in the CYP450 system.
2. Valproate is liquid fatty acid at room temperature, but can be reacted with a base to forms solid salt.
3. Interferes with platelet aggregation and can cause blood dyscrasias. Inhibits.
4. Effective 14 days after treatment.

Question 4

Phenytoin:

1. Half life?

Answer 4

Half life: 6 - 24 hours

Question 5

Phenytoin: inducer/ inhibitor?

Answer 5

Inducer

Question 6

Phenytoin: what deficiency can it cause and how?

Answer 6

Inhibits interstitial conjugated which causes folate deficiency.

Question 7

Cardiac effects when phenytoin is administered IV?

Answer 7

Hypotension, arrhythmias - should have cardiac monitoring with IV administration.

Question 8

Phenytoin effect on glucose metabolism?

Answer 8

Causes hyperglycaemia, glycosides and insulin inhibition.

Question 9

Phenytoin:

1. Type of kinetics
2. Therapeutic index wide or narrow.

Answer 9

1. First order kinetics then to zero order when the enzyme system is overwhelmed.
2. Narrow therapeutic index which needs to be monitored.

Question 10

Effects of phenytoin toxicity?

Answer 10

Blurred vision
Mydriasis
Brisk tendon reflexes

Question 11

Phenytoin: PO Bioavailability, Vd?

Answer 11

Bioavailability is good but oral absorption is slow, variable and can only be partial.

Vd- 70% of body weight

Question 12

Phenytoin: Class of antiarrhythmics?

Answer 12

Class 2b like lidocaine

Question 13

Phenytoin effect on TFT?

Answer 13

Doesn’t affect thyroid function but

Can have falsely low TFT after long term treatment.

Question 14

Which antiepileptic can be used to treat digoxin toxicity?

Answer 14

Phenytoin

Question 15

How is phenytoin metabolised?

Answer 15

By hepatic microsomal enzymes

Question 16

Side effects of phenytoin?

Answer 16

Nystagmus, gum over growth, blood disorders

Question 17

Phenobarbital: T/F

1. Most widely used anticonvulsant?
2. Lasts longer than phenytoin?
3. Used in generalise seizures?
4. Ineffective in absence seizures?
5. Highly protein bound?

Answer 17

False states are 1. And 5.

Protein burning is 20-45%

Question 18

Is phenytoin safe in pregnancy and why?

Answer 18

Not safe.

It is teratogenic and can cause fetal hydantoin syndrome like carbemazepine.

This syndrome causes intra-uterine growth retardation, microcephaly, craniofacial abnormalities and limb defects.

Question 19

Phenytoin stabilises active voltage gated sodium channels in the CNS? T/F

Answer 19

False, stabilises in the inactive state.

Question 20

Phenytoin excretion?

Answer 20

Initially excreted in the bile as inactive metabolites and reabsorbed before being excreted in the urine.

Small amount excreted renally unchanged.

Question 21

Carbemazepine effects in pregnancy?

Answer 21

Can cause spina big Ida and other neuro developmental problems after intrauterine exposure.

Question 22

Carbamazepine half life?

Answer 22

25 - 65 hours

Question 23

Carbamazepine link to Lupus?

Answer 23

Increases the risk of Lupus by nearly 90% in women.

Question 24

Carbamazepine:

Effect on serum sodium, WBC, platelets?

Answer 24

Reduce Na and WBC at normal levels.

Can cause life threatening thrombocytopenia.

Question 25

Can valproate be used in hepatic failure?

Answer 25

It is contraindicated in severe hepatic or renal failure.