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Drugs Used in Seizures (Anticonvulsants) (Other anticonvulsants…
Drugs Used in Seizures (Anticonvulsants)
Seizures result from episodic electrical discharges in cerebral neurons associated with prolonged depolarization, during which sustained, high-frequency, repetitive firing (DHFRF) occurs, followed by prolonged hyperpolarization. The goal of drug management is restoration of normal patterns of electrical activity
Mechanism of action
Decreased axonal conduction by preventing Na influx through fast Na-channels: Carbomazepine, Phenytoin
Increased inhibitory tone by facilitation of GABA-mediated hyperpolarization: Barbiturates, Benzodiazepines
Decreased excitatory effects of glutamic acid: Lamotrigine, Topiramate (blocks AMPA-R), Felbamate (blocks NMDA-R)
Decreased presynaptic Ca influx through type-T channels in thalamic neurons: Ethosuximide and Valproic acid
Primary anticonvulsants
Phenytoin
Blocks axonal Na channels in their inactivated state
Prevents seizure progression
Uses: seizure states
Side effects: CNS depression, gingival hyperplasia, hirsutism, osteomalacia ↓vit D, megaloblastic anemia ↓folate, aplastic anemia
Carbamazepine
Uses: seizure states, DOC for trigeminal neuralgia, bipolar disorder
Side effects: CNS depression, osteomalacia, megaloblastic anemia, aplastic anemia, exfoliative dermatitis, ↑ADH secretion (dilution hyponatremia)
Valproic acid
Also inhibit of GABA transaminase
Blockade of T-type Ca-channels
Uses: seizure states, mania of bipolar disorders, migraine prophylaxis
Side effects: hepatotoxicity, thrombocytopenia, pancreatitis, alopecia
Ethosuximide
Blockade of T-type Ca channels in thalamic neurons
Uses: absence seizures
Other anticonvulsants
Lamotrigine
Blocks Na channels and glutamate-R
Used in various seizures
Side effects: Stevens-Johnson syndrome
Levetiracetam
Mechanism unclear
Used in focal-onset and generalized tonic-clonic seizures
Topiramate
Blocks Na channels and glutamate-R and enhances GABA activity
Used in final seizures in adults and children (>age 2), also used in migraine prophylaxis
Side effects: weight loss
Felbamate
Block Na channels and glutamate-R
Used in seizure states
Side effects: aplastic anemia
Gabapentin
May effect Ca channels and neurotransmitter release, GABA effects
Used in seizure states, neuropathic pain