Download Anticonvulsants

Anticonvulsants
1. Which of these drugs increases the steady state concentration of phenytoin?
a. Phenobarbitone
b. Carbamazepine
c. Isoniazid <=
d. Ethanol
e. All of the above
2. Phenytoin
a. Is not effective against partial seizures
b. Accumulates in the endoplasmic reticulum of brain tissue <= true
c. Is poorly bound to plasma proteins – highly bound
d. Is mostly excreted unchanged by the kidneys – saturatable zero order hepatic metabolism with
<2% unchanged in urine
e. Suppresses seizures primarily by its action on channels <= blocks Na channels inhibiting the
generation of repetitive APs, prolongs the inactivated state
3. carbamazepine
a. is metabolized to active metabolites
b. in overdose causes seizures
c. is an enzyme inhibitor
d. is not a tricyclic
e. enhances sodium channel conductance
4. phenytoin
a. is lowly protein bound - highly
b. causes agranulocytosis in 5% of patients – very rare
c. ?
d. ?
e. can cause abnormalities of vitamin D metabolism <= correct, leading to osteomalacia
5. Match the drug and effect – which is INCORRECT?
a. Phenytoin – gum hypertrophy
b. Carbamazepine – ataxia
c. Phenobarbitone – enzyme induction
d. Ethosuximate – hirsutism <=
e. Valproate – idiosyncratic hepatic toxicity
6. A patient on phenytoin has a seizure and is found to have a low level, which is least likely to cause
this?
a. Phenobarbitone
b. Non-compliance
c. Hypoalbuminaemia – decreases the total (but not the free)
d. Disulfiram <= inhibits the metabolism
e. Erythromycin
7. With rergard to phenytoin, which is NOT true?
a. Metabolism is saturable within the therapeutic concentration range
b. Small changes in dose may cause swings from toxicity to sub-therapeutic levels
c. Steady state can be relied on to be achieved within 7 days of a dose change <= my take 4-6
weeks with higher doses
d. It may induce microsomal enzymes
e. Intravenous doses should be given over at least 20-30 minutes to avoid toxicity
8. A patient started on carbamazepine for episodes of partial seizures. After a month where she was
seizure free, she started having further seizures. What is the MOST likely cause?
a. The patient has developed a tolerance to carbamazepine
b. Carbamazepine is not the drug of choice for such seizures, hence the patient needs to be put on a
more suitable anticonvulsant
c. Initially carbamazepine has a low systemic clearance, however over time the clearance increases
requiring an increase in dose <=
d. She was not loaded with carbamazepine appropriately
e. All of the above
9. Your patient has abnormal LFTs, in particular an elevated AST. He tells you he is on medication
for fits, but can’t name it. Which is MOST likely to be his drug?
a. Phenytoin
b. Diazepam
c. Sodium valproate <=
d. Clonazepam
e. Ethosuximide
10. with regard to the general pharmacokinetics of anticonvulsants:
a. they are generally highly protein bound – only phenytoin and valproate
b. bioavailability is low - high
c. volumes of distribution are usually many time the free water volume – usually into TBW
d. clearance is hepatic <=
e. extraction ratios are high – usually low
11. concerning toxicity of phenytoin
a. nystagmus is a late complication – seen at therapeutic levels
b. alopecia is a complication - hirsuitism
c. increased deep tendon reflexes is a manifestation – mild peripheral neuropathey with diminished
deep tendon reflexes
d. vitamin D metabolism abnormalities can occur <=
e. agranulocytosis is a common manifestation - rare
12. carbamazepine is closely related to
a. vigabatrin
b. quinidine
c. sodium valproate
d. metoprolol
e. imipramine <=
13. Which of the following regarding carbemazepine is FALSE?
a. It is greater than 50% protein bound – 70%, but doesn’t displace
b. It has active metabolites – true, 10,11 epoxide has anticonvulsant activity
c. It induces p450 liver cytochromes - true
d. ?
e. ?
14. Patient on phenytoin is found to have a low blood phenytoin level. Which of the following is
LEAST likely to cause this?
a. Carbamazepine
b. Non-compliance
c. Disulfiram <= inhibits metabolism
d. Erythromycin - ?
e. Hypoalbuminaemia