anticonvulsants

• usually initiated after history of 2 seizures

• generalised

  • sodium valproate

    • except women of child bearing potentioal

      • low dose lamotrigine (\<200mg/day)

      • carbamazepine

• partial

  • lamotrigine

  • carbamazepine

• abrupt withdrawal potential to ppt seizures or status epilepticus

• increase risk of anxiety, depression and suicidlaity

• decrease mone mineral density and an increase fracture risk

sodium valproate

• all types of epilepsy

• adverse effects:

  • common

    • weight gain

    • tremor

    • GI disturbance

    • hair loss

  • thrombocytopenia

  • hepatic failure

  • pancreatitis

  • blood dyscrasia

• intreactions

  • most other anticonvulsants: raising blood levels

  • TCAs

  • BDZ

  • Warfarin

  • Aspirin

• Monitoring

  • CBC, LFT, electrolytes

    • bl, 3mo, annually

  • INR - dose decrease may be required

• regarded less sedating than other anticonvulsant

Carbamazepine

• Parital epilespises (first-line)

• also in generalised/mixed

• may worsen absence or myoclonic seizures

• Side effects

  • common

    • nausea / vomiting

    • sedation

    • dizziness and ataxia

  • Allergic rash - may be severe

  • leucopenia

  • hyponatraemia

    • action not required if sodium stable above 125mmol/L

  • hepatotoxicity

  • other blood dyscrasia

• intercations

  • increase plasma concentration

    • azole

    • macrolide

    • ssri

  • induces hepatic enzymes

    • oestrogen/progestogen

    • TCA

    • Warfarin

    • ccb

• monitoring

  • cbc, lft, electrolyte at baseline

• use slow release preparations

• drug of choice in pregnnacy

Lamotrigine

• ok for most forms of epilepsy

• alternate first line for partial

• side effects

  • common

    • allergic rash

    • headache

    • dizziness

    • blurred vision

  • serious allergic rash particularly

    • children

    • dose increased rapidly

    • dose increased rapidly in combination with sodium valproate

• Interactions

  • concentration increase by sodium valproate

  • decreased by enzyme inducing anticonvulsant oestrogens a nd progestogens

Phenytoin

• ok for most forms of epilepsy

• may worsen absence or myoclonic seizures

• side effects

  • common

    • headahce

    • tiredness

    • nausea

    • dizziness

    • drowsiness

  • allergic rash

  • hirsutism

  • coarsening of facial features

  • acne

  • gingival hyperplasia

  • hepatotoxicity

• interactions

  • induces hepatic enzymes; reduces effect of:

    • oestrogens and progestogens

    • TCAs

    • warfarin

    • CCB

    • statins

• Montoring

  • CBC, lft, electolytes

    • bl, 3mo, annually

• therapeutic drug monitorng is useful due to non-linear pharmacokinetics when adjusting dose or adding additional medicaitons

• narrow therapeutic index

• long term toxicity

Dose adjustments

• may be required for patients with impaired hepatic function

  • most metabolised by liver

  • lower doses required to avoid elevated serum drug levels

  • Gabapentin, pregabalin, levetiracetam excreted without metabolism by liver

    • no dose adjustmnet

• reduction in renal excretion and/or active metabolites

  • reduce dose

• lower doses in elderly

• routine therapeutic drug monitroing limited usefulness

  • except phenytoin

• small adjustments in phenytoin

special issues

• females iwth epilepsy

  • main concern = adequate contraception

  • especially carbamazepein adn phenytoin

    • increase metabolism of oestrogen and progestogen

      • reduce effectiveness

  • use at least 50µg of oestrogen

  • mid-cycle bleeding can be an indication that oestrogen dose is inadequate

  • oestrogen dose inc by:

    • 2x30ug/day

    • continuosuly for 3mo wiht 4d break between cycels

    • barrier used concurrently

  • may also reduce effectiveness of POP

  • barrier, depot, iucd, meirena = effective

  • Depo and some anticonvulsants associated with weight gain and lower BMD with long term use

  • if emergency contraception:

    • twice normal dose of ECP

    • IUCD within 5d could be offered as alternative

• preconception care

  • folic acid 5mg/day

  • continue first trimester

• pregnancy

  • carbamazepine or lamotrigine in doses \<200mg/day

• alcohol

  • CNS depressant

  • lowers seizure threshold

  • small amount probably ok

• epilepsy and driving

  • any person who has a seizure

  • single siezure; without diagnosis = same driving restrictions

  • commercial = loss of license