Use of intravenous valproate in three pediatric patients with nonconvulsive or convulsive status epilepticus.

OBJECTIVE: To report the pharmacokinetics of intravenous valproate (VPA) in children with generalized convulsive status epilepticus (GCSE) or nonconvulsive status epilepticus (NCSE). To provide loading and maintenance dosing for patients with hepatic induction secondary to concurrent anticonvulsants. CASE SUMMARY: Two patients (10 y, 34 mo) with GCSE refractory to benzodiazepines, phenobarbital, phenytoin, and pentobarbital received intravenous VPA. Apparent volume of distribution (Vd) following a 20 mg/kg loading dose was 0.29 L/kg. Maintenance infusions of 4-6 mg/kg/h produced steady-state total concentrations of 66 mg/L and 92.4 mg/L (unbound concentration 44.6 mg/L). Clearance ranged from 63-66 mL/h/kg. An eight-year-old with NCSE received intravenous VPA (13.4 mg/kg load followed by 9 mg/kg every 8 h). Total and unbound steady-state VPA concentrations were 32.9 mg/L and 21.2 mg/L, respectively. Elimination half-life was eight hours. DISCUSSION: We constructed a pharmacokinetic simulation using VPA parameters from children receiving mono- or polyanticonvulsants. Our Vd and elimination half-life rates were comparable with published pediatric values. Patients on hepatic inducers had clearance rates 2.5 times those of children receiving oral anticonvulsant polytherapy. Unbound fractions (48.3% and 66%) were significantly higher than normal. CONCLUSIONS: A 20 mg/kg loading dose should produce a concentration after the bolus dose of approximately 75 mg/L. Initial infusion should consider hepatic induction (noninduced = 1 mg/kg/h, polyanticonvulsant therapy = 2 mg/kg/h, and high-dose pentobarbital = 4 mg/kg/h). Adjustments should be based on response and serum concentrations.

Comparison of microparticle enzyme and fluorescence polarization immunoassays in pediatric patients not receiving digoxin.

Previously, investigators have measured endogenous digoxin-like immunoreactive substances (DLIS) in pediatric patients. Digoxin-like immunoreactive substances may cross-react with digoxin assays to produce false-positive digoxin concentrations; hence, the validity of digoxin concentrations in pediatric patients is questionable. The authors compared the presence and magnitude of apparent DLIS using the microparticle enzyme immunoassay (MEIA) AxSYM Digoxin II and the fluorescence polarization immunoassay (FPIA) TDx Digoxin II, in the serum of 80 pediatric patients who were hospitalized with normal serum creatinine but had not been administered digoxin. Patients ranged in age from 1 day to 16 years (mean age, 4.96 +/- 5.17 years). Serum creatinine and total bilirubin were 0.5 +/- 0.18 mg/dl and 1.3 +/- 0.17 mg/dl, respectively. Forty-eight percent of MEIA samples and 79% of FPIA samples had measurable DLIS values. Digoxin-like immunoreactive substance concentrations for the MEIA (0.07 +/- 0.09 ng/ml) and FPIA assays (0.1 +/- 0.1 ng/ml) were statistically different (p = 0.01); however, no sample had a DLIS value >0.38 ng/ml. A poor correlation was noted between patient age, serum creatinine, total bilirubin, and DLIS concentration. The MEIA and FPIA assays effectively minimized DLIS cross-reactivity making both technologies clinically acceptable for serum digoxin measurement in pediatric patients with normal serum creatinine and total bilirubin.