Anticonvulsants Flashcards Preview

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Flashcards in Anticonvulsants Deck (14):
1

Phenytoin

- for tonic-clonic generalized seizures and partial seizures
- suppresses seizures without the sedation of barbiturates
- use-dependent block: binds to the inactivated state of sodium channels
- induces CYP3A4 drugs
- adverse effects: gingival overgrowth in children, rickets/osteomalacia (affects it D and K metabolism and calcium absorption), overdose can cause ataxia, nystagmus, drowsiness, and CV collapse

2

Carbamazepine

- for tonic-clonic generalized seizures and partial seizures
- exacerbates absence and myoclonic seizures
- use-dependent block (binds to the inactivated state of sodium channels)
- induces CYP3A4 drugs so CYP3A4 inhibitors like erythromycin increases carbamazepine levels
- adverse effects: dizziness, ataxia, diplopia, headaches, agranulocytosis, aplastic anemia

3

Valproic Acid

- broad spectrum anticonvulsant also used to treat bipolar disorders and migraine
- use-dependent block
- increases GABA conc and inhibits calcium channels
- crosses membrane barriers --> not recommended for pregnant women
- inhibits the metabolism of itself and other drugs like phenobarbital
- adverse effects: idiosyncratic hepatotoxicity in pts under 2, pancreatitis

4

Ethosuximide (Succinimide)

- for absence seizures (first line)
- dose-dependent inhibition of calcium channels
- metabolized by CYP3A4, so CYP3A4 inhibitors like erythromycin increase plasma levels of succinimide
- crosses membrane barriers --> not recommended for pregnant women
- adverse effects: GI distress, headache, dizziness, skin rash

5

Acetazolamide (carbonic anhydrase inhibitors)

- for absence seizures and catamenial epilepsy
- usually used as an adjunct due to tolerance development
- increases CO2 levels in the brain --> hyper polarization and decreased neuron excitability
- adverse effects: dehydration, risk of kidney stone formation

6

Benzodiazepines

Currently approved by the FDA for seizure treatments: Clobazam, Clonazepam, Clorazepate, Diazepam
- decrease seizure threshold in patients with grand mal epilepsy (generalized tonic-clonic seizures)
- enhance the ability of GABA to open GABAa channels (increases freq of opening)
- many effects on the CNS such as sedation, hypnosis, anesthesia, and anti convulsion - inhibits development and spread of epileptiform activity
- contraindicated in pregnant women; detected in breast milk; can induce withdrawal symptoms and respiratory depression in neonate
- therapeutic index is large --> accommodates a wide range of dosing
- side effect: drowsiness
- additive deleterious effect when taken in combo with another CNS depressant like alcohol
- can induce a paradoxical reaction in elderly and younger patients
- tolerance can develop
- rapid discontinuation can cause serious withdrawal syndromes like convulsions and death
- IV diazepam or lorazepam is first line for status epilepticus treatment followed by phenytoin, phenobarbital, etc

7

Flumazenil

- benzo receptor antagonist
- for benzo overdose in naive patients only
- contraindicated for bento-dependent patients bc it can induce seizures and cardiac side effects

8

Phenobarbital / Primidone

- Primidone is metabolized to phenobarbital
- used to treat generalized tonic-clonic seizures
- other effects: dec BP/HR, rest depressant
- barbiturates increase duration of GABAa channel openings; GABA-mimetic at high concentrations
- inhibit glutamate receptors
- more pronounced CNS depressant effect than benzos
- contraindicated in pregnant women; detected in breast milk
- contraindicated in patients with porphyria (causes an increase in porphyrin precursors)
- metabolites of barbiturates lack pharm activity, unlike benzos
- potential drug interactions due to long-term use causing an increase in liver microsomal enzyme activity - decrease ability of Warfarin to act as an anticoagulant
- additive with other CNS depressants like alcohol
- can develop tolerance
- overdose can't be treated with Flumenazil

9

Lamotrigine

- uses: partial seizures, bipolar disorder, Lennox-Gastaut syndrome
- can cause Stevens-Johnson in children so it is primarily used in adults
- approved for mono therapy

10

Gabapetin

- uses: partial seizures, chronic pain conditions, migraine
- adjunctive therapy

11

Topiramate

- uses: broad spectrum - effective against refractory partial seizures; migraine
- adjunctive therapy
- can cause weight loss and memory impairment

12

Partial onset seizure with or without secondary generalization

carbamazepine and phenytoin are first line
but however are P450 enzyme inducers

13

Tonic-clonic, myoclonic, absence seizures

valproate is first line
ethoxysuximide also first line for absence seizures

phenytoin and carbamazepine are effective against tonic-clonic but not other types of generalized seizures

14

absence seizures

ethoxysuximide (succinimide) is first line along with valproate
valproate can protect against the tonic-clonic seizures that sometimes develop but rare risk of hepatotoxicity in children under 2 and skin rash (steven johnson)