- Anticonvulsants
- Management of status epilepticus (seizure activity > 30 mins)
- ABC, IV access, O₂
- 10mg diazepam (repeat after 10 mins)
- 15mg/kg phenytoin
- Thiopentone/propofol if resistant & ITU
- Consider paraldehyde
- Methods of action
- Increase GABA
- Facilitate GABA
- Benzodiazepines, barbituates
- GABA agonists
- Inhibit GABA transaminase
- Na⁺ channels
- Block inactive fast Na⁺ channels
- Stabilise pre-synaptic Na⁺ channels
- Lamotrigine (useful in pregnancy)
- Peri-op management of patients on anticonvulsants
- Pre-op
- Note nature, timing and frequency of seizures
- Drug history, take meds as usual
- Operative
- Consider regional, keep CO₂ normal, use atracurium as anticonvulsants can increase metabolism of aminosteroids. Avoid dystonic-inducing anti-emetics
- Post-op
- Early oral/ng feed, consider parenteral doses if needed
- Specific drugs
- Valproate
- Used for petit MAL and myoclonus
- Stabilises inactive fast sodium channels & inhibits GABA transaminase
- Side effects: Nausea, thrombocytopenia, neural tube defects
- 90% protein bound
- Hepatic metabolism
- Gabapentin
- Used in neuropathic pain
- Structural analogue of GABA
- Binds to voltage gated Ca²⁺ channels and may increase GABA & serotonin synthesis. Also inhibits voltage dependent Na⁺ channels
- Phenytoin
- Class Ib anti-arrhythmic
- Binds to refractory Na⁺ channels
- Most effective at neurons with a high firing rate
- Side effects: hirsutism, ataxia, coarse facies, nystagmus, megaloblastic anaemia, growth/mental retardation
- Potent enzyme inducer
- Bioavailability 90%
- Protein binding 90%
- Hepatic metabolism, usually 1st order but close to saturation so can be zero order