title: Increases in metabolism of valproate and excretion of 6beta-hydroxycortisol in patients with traumatic brain injury.
abstract: OBJECTIVE
  The objectives of this study were to determine the effect of brain trauma on the multiple pathways of metabolism of valproate and to evaluate the use of the urinary 6beta-hydroxycortisol to cortisol ratio in predicting changes in hepatic metabolism induced by brain injury.
  
  
  METHODS
  Fourteen patients with severe head injuries received a 15 mg kg(-1) loading dose and a maintenance dose of valproate to maintain therapeutic plasma concentrations. A minimum of one steady state trough blood sample and one dosage interval urine were collected during days 3-6 and during days 7-14 post-injury. Total and unbound valproate plasma concentrations were determined by gas chromatography-flame ionization detection (GC-FID) with and without ultrafiltration. Urinary valproate metabolites were measured by gas chromatography/mass spectrometry (GC-MS) (n = 10). Urinary 6beta-hydroxycortisol and cortisol concentrations were determined by high performance liquid chromatography (h.p.l.c.) (n = 14). Total intrinsic clearance (CL[int]) for valproate and individual formation clearances (CL[f]) to its major metabolites were calculated. Data obtained during baseline (days 3-6) were averaged for each patient and were compared with averaged data obtained from days 7 to 14 using a paired t-test.
  
  
  RESULTS
  Statistically significant increases in the CL(int), CL(f) of VPA glucuronide, 2-ene-VPA, and 4-OH-VPA pathways and the 6beta-hydroxycortisol to cortisol ratio were found. The percent change in the 6beta-hydroxycortisol to cortisol ratio correlated significantly with the changes in the CL(int) of valproate.
  
  
  CONCLUSIONS
  Brain trauma results in induction of multiple pathways of valproate metabolism and increases in the 6beta-hydroxycortisol to cortisol ratio, suggesting a non-specific enzyme induction in response to head injury.
authors.affiliation: Department of Pharmacy, School of Pharmacy, University of Washington, Seattle 98195, USA.
authors.forename: G D
authors.initials: GD
authors.lastname: Anderson
authors.forename: A B
authors.initials: AB
authors.lastname: Awan
authors.forename: C A
authors.initials: CA
authors.lastname: Adams
authors.forename: N R
authors.initials: NR
authors.lastname: Temkin
authors.forename: H R
authors.initials: HR
authors.lastname: Winn
mesh_terms: D000328:Adult; D000368:Aged; D000927:Anticonvulsants / Q000097:blood* / Q000627:therapeutic use / Q000652:urine; D001925:Brain Damage, Chronic / Q000097:blood / Q000378:metabolism / Q000652:urine; D001930:Brain Injuries / Q000097:blood / Q000378:metabolism* / Q000652:urine; D005260:Female; D006801:Humans; D006854:Hydrocortisone / Q000031:analogs & derivatives* / Q000652:urine; D008297:Male; D012640:Seizures / Q000517:prevention & control; D013997:Time Factors; D014635:Valproic Acid / Q000097:blood* / Q000627:therapeutic use / Q000652:urine
chemical_list: D000927:Anticonvulsants; C001380:6 beta-hydroxycortisol; D014635:Valproic Acid; D006854:Hydrocortisone