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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