Anti-Epileptic Drugs

Question 1

Phenytoin

Answer 1

ANTIEPILEPTIC
Action:
-decrease excitatory activity
-block sodium channels (keeps in refractory period, increases threshold)

Uses:
-DOC for tonic-clonic and partial seizures in adults

P. Kinetics:
-very narrow TI - care!
-half life varies
-poor and erratic absorption (take at same time each day/with food, e.g after breakfast)

ADRs:
-CNS depression (dizziness, drowsiness, headache)
-gingival hyperplasia (overgrowth of gums; tenderness, bleeding)
-NV (take w/ food)
-CV: hypotension, tachycardia
-bone marrow suppression (most dangerous)
-pregnancy, Fetal Hydantoin Syndrome (growth retardation, dislocated hips, mental deficiency, smaller brains, heart defects)
-nystagmus (uncontrolled eye movement)
-urine discoloration
-hirsutism
-allergic rash
-SJS (measles like rash)

Toxic Effects:
-CNS: sedation and cognitive impairment
-visual disturbances: nystagmus, diplopia
-ataxia (w/o coordination), unsteadiness

Implications: drug to drug interactions
-induction of hepatic enzymes = increased metabolism
-> decreased efficacy of warfarin (increased risk for clotting) and COCP
-CNS depressant: potentiation of CNS depression (no alc.)
-10-20 ug/mL; toxic > 30 ug/mL

Question 2

Ethosuximide

Answer 2

ANTIEPILEPTIC
-decrease excitatory activity
-block calcium channels

Use:
-DOC for absence seizures

ADRs:
-drowsiness and lethargy

Question 3

Barbiturates

Answer 3

ANXIOLYTIC, SEDATION, & ANTIEPILEPTIC
Action:
-increase inhibitory activity
-potentiate GABA (Cl is let in = too neg. = won’t fire)

Use:
-anti-convulsant
-anaesthesia

ADRs:
-narrow TI
-CNS depression (coma, death)
-suppress REM sleep
-sedation, drowsiness
-tolerance and dependence
-pregnancy
-no alc. or CNS depressants

Question 4

Levetiracetam

Answer 4

ANTIEPILEPTIC
Action:
-increase inhibitory activity
-used in adjunct therapy with phenytoin
-newer drug

Advantages:
-better tolerated
-smaller risk to fetus
-less drug interactions