anti epileptic drugs

Question 1

sodium valporate

Answer 1

1. increases GABA activity

2. first line for generalised seziures

Question 2

Carbamazepine

Answer 2

1. binds to sodium channels increasing their refractory period
2. first line for partial seizures

Question 3

Lamotrigine

Answer 3

1. sodium channel blocker

2. used second line for a variety of partial and generalised seizures

Question 4

phenytoin

Answer 4

1. binds to sodium channels increasing their refractory periods
2. no longer used first line due to side effect profile

Question 5

Groups of patients to consider when prescribing anti epileptics

Answer 5

1. patients who drive:
   - generally patients cannot drive for 6 months following a seizure.
   - For patients with established epilepsy they must be fit free for 12 months before being able to drive
2. patients taking other medications: antiepileptics can induce/inhibit the P450 system resulting in varied metabolism of other medications, for example warfarin
3. women wishing to get pregnant:
   - antiepileptics are generally teratogenic, particularly sodium valproate.
   - It is important that women take advice from a neurologist prior to becoming pregnant, to ensure they are on the most suitable antiepileptic medication.
   - Breast feeding is generally considered safe for mothers taking antiepileptics with the possible exception of the barbiturates
4. women taking contraception: both the effect of the contraceptive on the effectiveness of the anti-epileptic medication and the effect of the anti-epileptic on the effectiveness of the contraceptive need to be considered

Question 6

Carbamazepine is used for;

Answer 6

1. partial seizures

2, neuropathic pain (e.g. trigeminal neuralgia, diabetic neuropathy)

3. bipolar disorder

Question 7

Adverse effects of Carbamazepine

Answer 7

1. P450 enzyme inducer
2. dizziness/drowsiness/headache
3. visual disturbance
4. leucopenia and agranulocytosis
5. may exacerbate myoclonic/absence seizures

Question 8

adverse effects of Phenytoin

( chronic)

Answer 8

1. gingival hyperplasia - enlarged size of the gums, secondary to increased expression to platelet derived growth factor
2. Hirsutism
3. megaloblastic anaemia - secondary to altered folate metabolism
4. enhanced vitamin D metabolism causing osteomalacia

Question 9

adverse effects of Phenytoin

( teratogenic )

Answer 9

1. assoc with cleft palate and congenital heart disease

Question 10

adverse effects of Phenytoin

( idiosyncratic )

Answer 10

1. Fever
2. rashes, including severe reactions such as toxic epidermal necrolysis
3. hepatitis
4. Dupuytren’s contracture*
5. aplastic anaemia
6. drug-induced lupus