Anticonvulsant Drugs

1
Anticonvulsant Drugs

• Gerianne R. Bliss, M.D.
• Chuck Hensley, R.Ph.

2
Seizures

• Episodes of abnormal electrical activity in the
  brain.
• EEG changes
• Partial vs. Generalized seizures-see Table 20-1
• Status epilepticus-recurrent seizures without
  regaining consciousness
• Anticonvulsants suppress the formation or spread
  of abnormal electrical discharges in the brain

3
Partial and Generalized Tonic-Clonic Seizures

• Carbamazepine-po
• Active metabolite
• Block voltage-sensitive sodium channels
• Cause drowsiness and ataxia
• Inducer of Cytochrome p450
• Treat Trigeminal Neuralgia, Bipolar Disorder

4
Partial and Generalized Tonic-Clonic Seizures

• Phenytoin-IV or po
• Fosphenytoin-soluble form
• Inactive metabolite
• Block voltage-sensitive sodium channels
• Folate antagonism, inhibits calcium absorption,
  gingival hyperplasia
• Accelerates metabolism of other anticonvulsants
• Reduces levels of digoxin and vit K
• May worsen absence seizures

5
Partial and Generalized Tonic-Clonic Seizures

• Phenobarbital and primidone

6
Partial and Generalized Tonic-Clonic Seizures

• Valproate-po
• Valproic acid and divalproex sodium
• Inhibit voltage-sensitive sodium channels and
  T-type calcium channels
• Hepatic toxicity-mild to fatal
• Spina bifida and other birth defects
• Increase serum levels of lamotrigine, PB
• Broadest spectrum of activity, bipolar disorder

7
Partial and Generalized Tonic-Clonic Seizures

• Adjunct Drugs for Partial Seizures
• Gabapentin
• Increase release of GABA from central neurons
• Treat all forms of partial seizures
• Minimal adverse effects
• Lamotrigine
• Block voltage-sensitive sodium channels
• Treat partial seizures in adults and children
• Adverse effects-drowsiness, rash
• Topiramate
• Blocks voltage-sensitive sodium channels

8
Drugs for Generalized Absence,Myoclonic, or
Atonic Seizures

• Ethosuximide-po, long half-life
• Inhibits T-type calcium channels in the thalamus
• Safe and effective in children for absence
• Clonazepam-benzodiazepine, sedation
• Valproate-adjunct
• Lamotrigine-adjunct

9
Status Epilepticus

• Medical emergency
• IV diazepam or lorazepam followed by IV
  fosphenytoin or phenobarbital

10
Management of Seizure Disorders

• Review Table 20-4
• Control seizures with single dose therapy
• Two drugs with different mechanisms may control
  when a single drug is not adequate
• Measure serum levels
• Taper drugs slowly