MCQ's: Drugs used In Epilepsy Flashcards
Sodium valproate:
Mode of action?
- weakly blocks sodium ion channels.
- inhibits GABA transaminase, which would deactivate GABA and may also stimulate GABA synthesis.
Sodium valproate:
- Contra-indicated in children?
- Used to treat what type of seizures?
- Effect in GABA concentrations?
- Safe use in children down to 1 month age.
- Treats petit mal, generalised, mixed and partial seizures.
- Enhances concentrations of GABA.
Valproic acid:
- Metabolism?
- Form at room temperature?
- Effect on platelet?
- Effective for how long post Tx?
- 75% metabolised in the CYP450 system.
- Valproate is liquid fatty acid at room temperature, but can be reacted with a base to forms solid salt.
- Interferes with platelet aggregation and can cause blood dyscrasias. Inhibits.
- Effective 14 days after treatment.
Phenytoin:
- Half life?
Half life: 6 - 24 hours
Phenytoin: inducer/ inhibitor?
Inducer
Phenytoin: what deficiency can it cause and how?
Inhibits interstitial conjugated which causes folate deficiency.
Cardiac effects when phenytoin is administered IV?
Hypotension, arrhythmias - should have cardiac monitoring with IV administration.
Phenytoin effect on glucose metabolism?
Causes hyperglycaemia, glycosides and insulin inhibition.
Phenytoin:
- Type of kinetics
- Therapeutic index wide or narrow.
- First order kinetics then to zero order when the enzyme system is overwhelmed.
- Narrow therapeutic index which needs to be monitored.
Effects of phenytoin toxicity?
Blurred vision
Mydriasis
Brisk tendon reflexes
Phenytoin: PO Bioavailability, Vd?
Bioavailability is good but oral absorption is slow, variable and can only be partial.
Vd- 70% of body weight
Phenytoin: Class of antiarrhythmics?
Class 2b like lidocaine
Phenytoin effect on TFT?
Doesn’t affect thyroid function but
Can have falsely low TFT after long term treatment.
Which antiepileptic can be used to treat digoxin toxicity?
Phenytoin
How is phenytoin metabolised?
By hepatic microsomal enzymes
Side effects of phenytoin?
Nystagmus, gum over growth, blood disorders
Phenobarbital: T/F
- Most widely used anticonvulsant?
- Lasts longer than phenytoin?
- Used in generalise seizures?
- Ineffective in absence seizures?
- Highly protein bound?
False states are 1. And 5.
Protein burning is 20-45%
Is phenytoin safe in pregnancy and why?
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.
Phenytoin stabilises active voltage gated sodium channels in the CNS? T/F
False, stabilises in the inactive state.
Phenytoin excretion?
Initially excreted in the bile as inactive metabolites and reabsorbed before being excreted in the urine.
Small amount excreted renally unchanged.
Carbemazepine effects in pregnancy?
Can cause spina big Ida and other neuro developmental problems after intrauterine exposure.
Carbamazepine half life?
25 - 65 hours
Carbamazepine link to Lupus?
Increases the risk of Lupus by nearly 90% in women.
Carbamazepine:
Effect on serum sodium, WBC, platelets?
Reduce Na and WBC at normal levels.
Can cause life threatening thrombocytopenia.
Can valproate be used in hepatic failure?
It is contraindicated in severe hepatic or renal failure.
