Urinary excretion of phenobarbital and its metabolite p-hydroxyphenobarbital in convulsing and non-convulsing patients

As part of an investigation of phenobarbital (PB) pharmacokinetics in patie nts with status epilepticus (SE), urinary excretion of PB and its main meta bolite, hydroxyphenobarbital (HPB), was studied in patients who had an epis ode of SE, as well as in non-convulsing ones. Eleven in-patients were studi ed:(group 1) five patients (4 M + 1 F; 48 +/- 28 years old; 64 +/- 6 kg bod y weight; mean +/- SD) with convulsive status epilepticus, and (group 2) si x patients (5 M + 1 F; 37 +/- 13 years old; 71 +/- 15 kg body weight) with epilepsy, seizure-free at the moment of PB administration and without estab lished anti-epileptic therapy. All subjects received a single intravenous d ose of PB (15 mg/kg) at a rate of 100 mg/min. PB and HPB concentrations wer e measured by high performance liquid chromatography with UV detection at 2 20 nm in urine samples collected throughout 24 h. The comparison of pharmac okinetic parameters of urinary excretion of PB and HPB showed a statistical ly significant difference in the values of recovery of HPB and total barbit urate (higher values in the patients with SE) in 24 h urine. Differences in the excretion of PB between the two groups of patients - higher values in the patients who had had an episode of SE, and in urine flow - slightly ele vated volumes in the same group, failed to reach statistical significance, probably due to the small number of participants in the study.