Pharmacokinetics of High-dose Thiopental in Pediatric Patients with Increased Intracranial Pressure

This study was conducted on 10 pediatric patients in whom intracranial hypertension stemming from head injury was reduced by high-dose thiopental administered for a prolonged period. All children showed a favorable recovery of their neurological functions. The total dose normalized to body weight averaged 335 +/- 135 mg/kg, and the mean treatment duration was 93.0 +/- 37.1 h. Data analysis was modeled for each patient to cover all the doses on the whole plasma thiopental concentration-time curve, according to a one-compartment open model. A better fit was obtained using a linear model rather than a Michaelis-Menten elimination model. Model selection was guided by evaluation of the minimum objective function, the weighted residuals, and the Akaike criterion. Thiopental pharmacokinetic parameters in pediatric patients were compared with those determined in an adult control group with similar total doses and durations of treatment. No significant difference was found between the two groups in spite of a 33% decrease of the elimination half-life in children (11.7 +/- 5.7 h) compared with adults (17.5 +/- 9.03 h). The mean values obtained were 2.42 and 2.19 ml/min/kg for total clearance and 2.18 and 2.90 L/kg for Vd in pediatric and adult groups, respectively. The linear regression of pharmacokinetic parameters in terms of age was not significant. When high doses of thiopental were administered over a prolonged period, the pharmacokinetic parameters computed for pediatric patients did not differ from those obtained in adults.