Multiple intravenous doses of paracetamol result in a predictable pharmacokinetic profile in very preterm infants

Aim The therapeutic options available to treat neonatal pain are limited, and one alternative for nonopioid systemic treatment is paracetamol. However, pharmacokinetic data from prolonged administration of intravenous paracetamol in neonates are limited. The aim of this study was to present pharmacokinetics after multiple dose of intravenous paracetamol in very preterm infants of <32 weeks' gestation. Methods Fifteen very preterm infants received five, six-hourly doses of intravenous paracetamol (7.5 mg/kg). Blood samples were taken to measure paracetamol, glutathione and hepatic function, together with urine samples for paracetamol metabolites. Results A two-compartment pharmacokinetic model gave the best fit for all individual patients and resulted in a predictable pharmacokinetic profile. The estimated pharmacokinetic population parameters were volume of distribution 0.764 ± 0.225 L/kg, elimination rate constant (k_e) 0.117 ± 0.091/h and intercompartment rate constants k₁₂ 0.607 ± 0.734/h and k ₂₁ 1.105 ± 0.762/h. Conclusion Our study found that multiple doses of intravenous paracetamol resulted in a predictable pharmacokinetic profile in very preterm infants. Increases in postmenstrual age and weight were associated with increased clearance. No evidence of hepatotoxicity was found.