Pharm: Anti Epileptics Flashcards
What types of seizures do drugs that enhance sodium channel inhibition treat?
Focal and secondary generalized seizures.
NOT absence
Define Ictal.
ictal refers to a physiologic state or event such as a seizure.
Phenytoin
MOA: acts of Na channels extending the refractory period which leads to inhibition the channel activation.
Indications: focal and tonic clonic seizures
AE: follows zero order kinetics so it needs to be monitored constantly during use
- alters plasma levels of oral contraceptives
- gingival hyperplasia
Carbamazepine
MOA: acts of Na channels extending the refractory period which leads to inhibition the channel activation.
Indications: focal seizures
AE: induces its own metabolism by the liver so chronic use involves increasing the dose over time
Lamotrigine
MOA: acts of Na channels extending the refractory period which leads to inhibition the channel activation.
Indications: focal seizures
AE: skin rash
Lacosamide
MOA: acts of Na channels extending the refractory period which leads to inhibition the channel activation.
Indications: adjunctive therapy for focal seizures
AE: dizziness, headache, nausea, diplopia
What types of seizures do drugs that block T-type Calcium channels treat?
Mainly absence seizures
T-type calcium channels are voltage-gated and moderate calcium current in the thalamus and cardiac muscle
Ethosuximide
MOA: Block T-type calcium channels
Indications: absence seizures
Valproic Acid
MOA: Block T-type calcium channels, also sodium channel blocker, and glutamic acid decarboxylase inhibitor (more GABA)
Indications: absence seizures when ethosuximide is ineffective
-focal seizures as alternate to phenytoin and carbamazepine
AE: hepatotoxicity
What types of seizures do drugs that block High Voltage Activated (HVA) calcium channels treat?
All types of seizures EXCEPT absence seizures (focal, secondary generalized, generalized).
(HVA calcium channels are located on presynaptic neurons that, when signals, allow vesicles to release neurotransmitters)
Gabapentin
MOA: Blocks HVA calcium channels (anti-seizure)
-also increases GABA content in neural glial cells
Indications: focal, secondary generalized, generalized seizure (NOT ABSENCE)
Pregabalin
MOA: blocks HVA calcium channels
Indications: focal seizures, secondary generalized, generalized (NOT ABSENCE)
-useful for patients with liver insufficiency because it is metabolized in the kidneys
Diazepam, Lorazepam, Midazolam
MOA: bind GABA-a receptors and enhance chloride current when GABA binds.
Indications: focal and tonic-clonic seizures
Clonazepam
MOA: indirect inhibition of T-type calcium channels in the thalamocortical circuits.
Indications: absence seizures
Phenobarbital
MOA: binds GABA-a receptor prolonging the activations and opening of the chloride channel, a weak agonist that doesn’t require GABA to bind to have its effect.
Indications: focal and tonic clonic seizure, acute resistant seizures
AE: many due to its weak agonist potential
Vigabatrin
MOA: structural analog of GABA that binds and irreversibly inhibits the enzyme GABA transaminase preventing the breakdown of the “real” GABA neurotransmitters.
Indications: infantile spasms and refractory focal epilepsy
AE: bilateral visual field defects and atrophy of peripheral retinal nerve fiber layers
-so any pt. on this medication should have eyes checks periodically
Tiagabine
MOA: competitive inhibitor of GABA transporters preventing the re-uptake of GABA into neurons. (“Tidal wave” of GABA)
Indications: potentiates action of GABA-a modulators (BZs, barbs, ethanol)
AE: confusion, sedation, amnesia, ataxia
What is the major side effect of all the glutamate receptor antagonists?
Behavioral Adverse Effects
Felbamate
MOA: NMDA receptor antagonist
Indications: refractory epilepsy
-potent without the sedative side effects
AE: aplastic anemia and liver failure
Rufinamide
MOA: prolongs refractory period of sodium channels, at HIGHER doses inhibits NMDA receptors.
Indications: refractory seizures, focal seizures and drop attacks in Lennox-Gastaut syndrome.
AE: not as severe as felbamate, so an alternative med for refractory epilepsy
Describe the treatment procedure for status epilepticus.
- IV Lorazepam or Diazepam
- if seizures continue: IV fosphenytoin
- ” “ : Phenobarbital
- ” “ : general anesthesia
Which of the anti-seizure meds is the most teratogenic?
Valproic Acid
