RESUMO
OBJECTIVES: To determine the pharmacokinetics of pentobarbital in neonates, infants, and young children with congenital heart disease after open-heart surgery. STUDY DESIGN: Thirty-five subjects (3.0 days-4.4 years) after open-heart surgery who received pentobarbital as standard of care were enrolled. Serial pharmacokinetic blood samples were obtained. A population-based, nonlinear mixed-effects modeling approach was used to characterize pentobarbital pharmacokinetics. RESULTS: A two-compartment model with weight as a co-variate allometrically expressed on clearance (CL), inter-compartmental clearance, central (V1) and peripheral volume of distributions, bypass grafting time as a co-variate on CL and V1, and age and ventricular physiology as co-variates on CL best described the pharmacokinetics. A typical infant (two-ventricle physiology, 6.9 kg, 5.2 months, and bypass grafting time of 60 minutes) had a CL of 0.12 L/hr/kg, V1 of 0.45 L/kg, and peripheral volume of distributions of 0.98 L/kg. The bypass grafting effect was poorly estimated. For subjects <12 months age, an age effect on CL remained after accounting for weight and was precisely estimated. CONCLUSIONS: Pentobarbital pharmacokinetics is influenced by age and weight. Subjects with single-ventricle physiology demonstrated a 15% decrease in clearance when compared with subjects with two-ventricle physiology.
Assuntos
Cardiopatias Congênitas/cirurgia , Hipnóticos e Sedativos/farmacocinética , Pentobarbital/farmacocinética , Fatores Etários , Peso Corporal , Pré-Escolar , Humanos , Hipnóticos e Sedativos/sangue , Lactente , Recém-Nascido , Pentobarbital/sangue , Fatores de TempoRESUMO
A single i.v. dose (0.1 mmol Be2+/kg) of beryllium chloride prolonged the duration of pentobarbital-induced sleep and zoxazolamine-induced paralysis, in rats. The effects are correlated with changes of the pharmacokinetic parameters and with the in vitro inhibition of both aliphatic and aromatic hydroxylation of pentobarbital and zoxazolamine. In vitro N-demethylation of meperidine and aminopyrine was partially inhibited while O-demethylation of quinidine was unaffected by liver microsomes of rats pretreated with beryllium salt. The findings give clues that beryllium chloride inhibits some forms of cytochrome P-450, especially those responsible for hydroxylation of substrates, like pentobarbital and zoxazolamine.
Assuntos
Berílio/farmacologia , Microssomos Hepáticos/enzimologia , Animais , Comportamento Animal/efeitos dos fármacos , Berílio/administração & dosagem , Citocromos b5/metabolismo , Depressão Química , Hidroxilação , Injeções Intravenosas , Masculino , NADPH-Ferri-Hemoproteína Redutase/metabolismo , Pentobarbital/sangue , Pentobarbital/farmacologia , Ratos , Ratos Endogâmicos , Reflexo/efeitos dos fármacos , Sono/efeitos dos fármacos , Zoxazolamina/sangueRESUMO
The pharmacokinetics of pentobarbital were examined in 11 children with Reye syndrome, hypoxic encephalopathy, or acute head injury. Nine of these patients were hypothermic (less than 32 degrees C). The total systemic clearance and volume of distribution at steady state of pentobarbital were significantly reduced in these patients when compared to previous data in normothermic adult volunteers following intravenous doses of pentobarbital. Pentobarbital elimination half-life was not significantly different from control values. The diminished systemic clearance of pentobarbital may result from decreases in intrinsic enzyme activity that accompany hypothermia, as well as hepatic dysfunction in patients with Reye syndrome. Less extensive distribution of pentobarbital is likely the result of either differences in body fat composition or hypothermia-induced decreases in regional blood flow. The reduced clearance and distribution of pentobarbital may partially explain the enhanced reduction in cerebral metabolism that occurs on addition of hypothermia to barbiturate therapy in patients with elevated intracranial pressure.