Antiepileptics

Question 1

Antiepileptic drugs

Answer 1

Treatment of status epilepticus : DIAZEPAM

Prevention of seizures : PHENOBARBITAL, PHENYTOIN, VALPROIC ACID

Question 2

Phenobarbital

Answer 2

CNS depressant.
Decr Ach, NE, Glu release, GABA-mimetic.
PO bioavailability, tmax = 4-8h
(Dosage -> steroids, doxycycline, quinidine, phenylbutazone)

SE : sedation, drowsiness, ataxia, polyphagia, polyuria (thrombocytopenia, neutropenia).

Dosage : 1-5 mg/kg PO
2-4 mg/kg IV bolus - Status Epilepticus !!!! (& 2-15 mg/kg IV pentobarbital).
As adjuncts : clonazepam, chlorazeopate (2-6 mg/kg, bid)

Question 3

Diazepam, Midazolam

Answer 3

Dogs : controls Status Epilepticus !! Not orally.
Dose : IV bolus 5-10 mg/kg, followed by inf 2-5 mg/h,
per rectum 0,5-2 mg/kg up to 3X in 24h.

Cats : maintenance therapy : 0,25-0,5 mg/kg PO, bid-tid
status epilepticus : 0,5-2 mg/kg IV

Horses : long elimination half-life (7-22 h). Anticonvulsant of choice 5-20 mg/dose IV.
Seizures : 25-50 mg/dose IV, foals : 0,02-0,4 mg/kg IV

Question 4

Clonazepam

Answer 4

Dogs : tolerance is developed less rapidly. Oral maintenance therapy (as an adjunct to PB : 0,1-0,5 mg/kg/day OR alone : 0,5 mg/kg), highly absorbed orally.

Sometimes diarrhea.

Question 5

Phenytoin

Answer 5

A membrane stabilizing agent -> GABA enhancing activity
=> cardiac anti-dysrhythmic activity & anticonvulsant

Short elimination half-life in dog, v long in cats (toxicity!). Difficult to achieve therapeutic [] in dogs (rapid metabolism)

Carbamazepine : similar, but less SE (effective in psychomotor epilepsy)

Question 6

Primidone

Answer 6

= 2-deoxy analogue of PB
Metabolites -> antiepileptic activity

DONT use with barbiturates !!!

Question 7

Na / K Bromide

Answer 7

Monotherapy : 2,5 mg/ml
With PB : 1-1,5 mg/ml

Long half-life : 21-24 days (dogs)
Dose : 20-40 mg/kg once a day

SE : sedation, pruritic skin lesions, polydipsia, pleurae, ataxia, stupor.