Excreted Unchanged %
19-31
Half-Life (Normalesrd) Hours
80-117/117-160
Plasma Protein Binding %
48-54
Volume Of Distribution L/Kg
0.51-0.57
Dose For Normal Renal Function
50-100 mg q8-12h
Adjustment For Renal Failure Method
I
Adjustment For Renal Failure Gfr, Ml/Min >50 [Recommended Level]
q8-12h [D]
Adjustment For Renal Failure Gfr, Ml/Min 10-50 [Recommended Level]
q8-12h [D]
Adjustment For Renal Failure Gfr, Ml/Min <10 [Recommended Level]
q12-16h [D]
Supplement For Dialysis [Recommendation Level]: Ihd
IHD: Dose before dialysis; dose after dialysis, [D]
Supplement For Dialysis [Recommendation Level]: Pd
PD: normal dose, [B]
Supplement For Dialysis [Recommendation Level]: Crrt
CRRT: Normal dose and measure levels, [B]
References
Browne TR. The pharmacokinetics of agents used to treat status epilepticus. Neurology. 1990; 40: 28-32. [PMID: 2185438] / Browne TR, Evans JE, Szabo GK, Evans BA, Greenblatt DJ. Studies with stable isotopes II: Phenobarbital pharmacokinetics during monotherapy. J Clin Pharmacol. 1985; 25: 51-8. [PMID: 3973064] / Mattson RH. Parenteral antiepileptic/anticonvulsant drugs. Neurology. 1996; 46: S8-13. [PMID: 8649613] / Palmer BF. Effectiveness of hemodialysis in the extracorporeal therapy of phenobarbital overdose. Am J Kidney Dis. 2000; 36: 640-3. [PMID: 10977799] / Riva R, Albani F, Contin M, Baruzzi A. Pharmacokinetic interactions between antiepileptic drugs. Clinical considerations. Clin Pharmacokinet. 1996; 31: 470-93. [PMID: 8968658] / Rogvi-Hansen B, Gram L. Adverse effects of established and new antiepileptic drugs: an attempted comparison. Pharmacol Ther. 1995; 68: 425-34. [PMID: 8788565] / Shihab-Eldeen AA, Peck GE, Ash SR, Kaufman G. Evaluation of the sorbent suspension reciprocating dialyser in the treatment of overdose of paracetamol and phenobarbitone. J Pharm Pharmacol. 1988; 40: 381-7. [PMID: 2901467]
Toxicity Notes
May cause excessive sedation and increase osteomalacia in ESRD. Charcoal hemoperfusion and hemodialysis more effective than peritoneal dialysis. For poisoning. Up to 50% unchanged drug excreted in urine with alkaline diuresis. Substantial removal during hemodialysis and CRRT may result in low levels; follow levels closely. Usual oral dosage for adults is 100-300 mg daily. Although the drug is often given tid or qid, there is no advantage in dividing the daily dosage because of the long half-life. The daily dose can be given at bedtime.