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19 Cards in this Set
- Front
- Back
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What is epilepsy?
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Epilepsy is a brief disorder of brain function associated with sudden abnormal discharge of nerves.
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Describe the classification of epilepsy.
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Partial:
- simple - complex (reduced consciousness) - secondarily generalised Generalised: loss of consciouness - Absence - Tonic-clonic - Tonic or Clonic or Atonic; Myoclonic Status epilepticus: continuous succession of fits |
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What are the symptoms of Partial Seizures?
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Motor: e.g. "Jacksonian march"
Sensory: e.g. hallucinations of smell, taste, hearing Psychic: e.g. "deja vu", automatism Sensory/psychic symptoms common in temporal lobe epilepsy |
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What are the symptoms of Tonic-clonic (grand mal) seizures?
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- Mood change +/- aura
- Tonic muscle spasm, loss of consciousness - Clonic stage:jerking, salivation, +/- incontinence - Confusion/headache |
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What are symptoms of generalised seizures?
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Absence (petit-mal): starts in childhood, transient loss of consciousness but not posture (~10sec)
Myoclonic: jerking of limbs Atonic: loss of posture |
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List the mechanisms of action of anticonvulsants.
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- Potentiate GABA; benzodiaszepines, barbiturates, gabapentin (?)
- GABA analogue: tiagabine - Reduce GABA breakdown; vigabatrin, balproate (?) - Block Na+ channels; carbamazepine, phenytoin, topiramate |
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How do anticonvulsants work?
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Dose-related CNS depression (all anticonvulsants)
Cortical (sedation): e.g. benzodiazepines & barbiturates Cerebellar (ataxia, nystagmus, diplopia): e.g. phenytoin |
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Describe the uses of different anticonvulsants.
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Valproate - most types (often used for generalised)
Carbamazepine, phenytoin - most types, except absence (carbamazepine often used for partial epilepsies) Clonazepam - myoclonic, absence Ethosuximide - absence Vigabatrine, lamotrigine, gabapentin, topiramate, tiagabine, levetiracetam - "add on" therapy |
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Carbamazepine
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- Also used for trigeminal neualgia
- Liver enzyme induction - Marrow depression, jaundice, gastrointestinal upset, rashes, hypersensitivity - need to monitor blood |
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Phenytoin
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- Narrow safety margin, cerebellar effects
- Phenytoin metabolism can become saturated with zero order kinetics - Liver enzyme induction: drug interactions; folate, Vit D & neonatal Vit K deficiency - Rashes, marrow depression, lymphadenopathy - Costmetic effects: gum enlargement, acne, hairiness, coarse features |
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Vigabantrin, lamotrigine, gabapentin, topiramate, tiagabine, levetiracetam
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- For epilepsy uncontrolled by other drugs
- All cause CNS effects Vigabatrin - GI upset, behavioural problems Lamotrigine - Rashes Gabapentine - GABA analogue; headache, tremor Topiramate - like phenytoin but simplet pharmacokinetics & less adverse effects; teratogenic Tiagabine: GABA analogue; causes drowsiness and confusion Levetiracetam: inhibits burst firing; dizziness, sedation |
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Ethosuximide
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- Used only for absences
- Rashes GI upset, marrow depression |
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Long-acting barbiturates (e.g. phenobarbitone)
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- 2nd choice drugs, dangerous in overdose
- sedation, learning problems - rashes - liver enzyme induction |
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Valproate
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- Gastrointestinal upset, marrow depression
- Severe hepatitis (rare, usually in children with other medical problems) - Hair loss |
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Benzodiazepines
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Clonazepam:
- especially useful in myoclonic, absence - sedation Diazepam: - i.v. in status epilepticus |
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Describe the drug interactions of anticonvulsants.
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Pharmakokinetic:
Liver enzymes not always predictable: - competing drugs: increases drug levels e.g. valproate & phenobarbitone - Enzyme induction: reduces drug levels e.g. warfarin, steroids, contraceptives Protein binding sites: e.g. salicylates & phenytoin Pharmacodynamic: e.g. interaction with other CNS depressants |
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Describe the link between pregnancy and anticonvulsants.
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- Anticonvulsants cause abortions & fetal abnormalities
- Phenytoin affects palate, heart ? due to reduced folate & Vit K - Valproate causes spina bifida - Withdrawal of anticonvulsants dangerous - Phenytoin, topiramate & valproate are particularly likely to cause problems |
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Describe the aim of treatment of epilepsy.
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- Treat the whole person (including social and psychiatric problems)
- Remove causal/precipitating factors - Prevent fits by drugs - Minimise adverse effects - Monotherapy preferable |
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What should be done if there is difficulty controlling fits?
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- Right diagnosis/drug?
- Monitor plasma levels: > patient compliance? > in therapeutic range? - Dose requirements variable - Never withdraw drug suddently: > may get status epilepticus |
