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Table 2 Bioavailability and pharmacokinetic data of antiepileptic drugs [113]

From: Antiepileptic drugs in critically ill patients

Antiepileptic drug agent Bioavailability (PO formulation) Protein binding Half-life Metabolism Elimination
Brivaracetam Almost completely absorbed ≤ 20% ~  9 h Hydrolysis (primary route) CYP2C19 ≥ 95% renally
Carbamazepine 75–85%
Total daily intravenous dose should be equivalent to 70% of previous total daily oral dose
75–95% Range: 30–60 h
After autoinduction:
12–17 h
> 90% by CYP3A4 72% renally
Clobazam 87% 80–90% 36 to 42 h Hepatic via CYP3A4 and to a lesser extent via CYP2C19 82% renally
Clonazapam ~ 90% ~ 85% 17–60 h Glucuronide and sulfate conjugation < 2% renally as unchanged drug
Diazepam > 90% 98% Parent drug: ~ 60 to 72 h; metabolite ~ 152 to 174 h CYP3A4 and 2C19 Renally
Eslicarbazepine > 90% < 40% 13–20 h Hydrolytic first-pass metabolism 90% renally
Fosphenytoin 100% (intramuscular formulation) 95–99% 12–28.9 h CYP2C9 CYP2C19 Renally
Lacosamide 100% < 15% 13 h CYP3A4, CYP2C9, CYP2C19 95% renally
Lamotrigine 98% 55% 25–70 h Conjugation 94% renally
Levetiracetam 100% < 10% 6–8 h Hydrolysis 66% renally
Lorazepam 90% ~ 91% 12–18 h Conjugation 88% renally
Midazolam      
Oxcarbazepine Readily absorbed 40% Active metabolite: 9–11 h Glucoronidation 95% renally
Pentobarbital 45% to 70% 15–50 h Hydroxylation and glucuronidation < 1% renally as unchanged drug
Perampanel Completely and rapidly absorbed 95% ~ 105 h CYP 3A4/5 primary;
lesser extent CYP 1A2/2B6
22% renally
Phenytoin 20–90% 90–95% 7–42 h CYP2C9, 2C19 (major) and 3A4 (minor) < 5% renally as unchanged drug
Phenobarbital ~ 95–100% 50% Longest half-life
46–136 h
CYP450 and UGT mediated 25–50% renally
Topiramate 80% 15–41% IR: 21 h
ER: 31–56 h
No extensive metabolism 70% renally
Valproic acid 90% 80–90% 9–16 h CYPs 2C9, 2C19, 2A6, UGT-glucuronidation 70–80% renally
Zonisamide Rapid and complete absorption 40% 50–68 h CYP 3A4 60% renally
  1. CYP Cytochrome, ER Extended Release, IR Immediate Release, PO By mouth, UGT Uridine diphosphate-glucuronyltransferase