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Table 1 Relationship between age, weight, valproic acid (VPA) formulation, daily VPA dose, average VPA levels, and concentration/dose (C/D) ratio × 1000 mean ± SD and range across cases

From: Valproic acid autoinduction: a case-based review

Cases Age Wt. (kg) Diagnosis Hospital Duration Formulation VPA dose (mg/day) VPA level (μg/mL) C/D ratio × 1000a No. of VPA Levels Mean C/D ratio × 1000: mean ± SD, range# Comments
Case 1* 34 85 Schizophrenia
Seizure disorder
 > 3 years VPA 5250 87 17 44 15 ± 2.6, range = 10–21 Significantly lower C/D ratio than the normal range between 112 and 132 µg/mL, suggesting faster VPA metabolism
 < 1 year DVPS 2000 78 39 7 39 ± 6.3, range = 28–48 Higher C/D ratio with DVPS than VPA in case 1, suggesting significantly slower DVPS metabolism than VPA
Case 2* 66 90 Bipolar Disorder
Substance Use disorder
8 weeks DVPS 4000 67 17 10 25 ± 5.6, range = 17–33 Significantly lower C/D ratio than the normal range between 112 and 132 µg/mL, suggesting faster VPA metabolism
Case 3* 70 71 Tuberous Sclerosis  > 4 years DVPS 10,500 10 12 137 8 ± 3.5, range = 3–20 Lowest C/D ratio of all cases, suggesting robust autoinduction with DVPS
New Case 51 71 Bipolar disorder
Methamphetamine use disorder
Recent Traumatic Brain Injury
22 days VPA 5000 98.8 19.8 7 18.6 ± 2.9, range = 13–20 Similar C/D ratio to case 1 & 2, suggesting similar rate of autoinduction with VPA
  1. *Reference = Jackson et al. (2015) VPA: valproic acid; DVPS: divalproex sodium; C/D = Mean concentration/dose ratio (therapeutic range between 112 to 132 µg/mL); Number of VPA levels drawn over total hospitalization
  2. #Mean C/D ratio × 1000: mean ± SD, range; Calculated from the total number of VPA levels during hospital duration
  3. aC/D ratio × 1000; Calculated from the last final VPA dose and the level at that dose