Anticonvulsants Flashcards
What is the onset, half time, and metabolism of Phenytoin?
“Onset = rapid IV
90% PB
0.7L/kg
E1/2t = 20 hrs+ = must maintain within tight serum level parameters”
“Hepatic microsomal enzymes to inactive metabolites. 2% unchanged in urine
Mechanism of action of Phenytoin?
“Antiepileptic – partial or generalized sz
Class Ib antiarrythmic”
“Decreases neuronal excitability and inhibits NT by ↓sodium and calcium ion transport across neuronal cell membranes. = stabilizes membrane to hyperexcitability
Tx of ventricular arrhythmias”
What is the dosage of Phenytoin?
10-25mg/kg @ 50mg/min
1-3 mg/kg/min
New seizure – typically load with 1gm, depending on pts weight/age
Prophylaxis = 100-200mg IV q4hrs at
What are the adverse effects of Phenytoin?
"Hypotension, Bradycardia Arrhythmias CV collapse Pain/thrombophlebitis CNS toxicity – tight parameters Nystagmus Hepatotoxicity Confusion, Slurred speech Stevens Johnson syndrome"
What are the contraindications of Phenytoin?
"Pregnancy unless benefits outweigh risks. Porphyria Hepatic dysfunction Bradycardia Av block Caution in elderly hypoalbuminemia"
