Objective Based on recently published data, a local initiative in our neonatal intensive care unit has led to a pain protocol, in which preterm infants experiencing pain are treated with paracetamol intravenously. We present a case series of nine preterm infants with a gestational age below 32 weeks, in whom paracetamol serum concentrations were determined after prolonged administration of paracetamol 15 mg/kg at 6-h intervals intravenously.

Methods Nine infants (mean gestational age 28.6 weeks, range 25.9–31.6) received 15 mg/kg paracetamol at 6-h intervals.

Results Adequate analgesia with paracetamol monotherapy as measured by a PIPP score below 12 was attained in seven infants. The serum concentration was determined after 2–3 days of therapy. The median interval between drug administration and serum level was 4 h (range 1–20). The median level of paracetamol was 29 mg/l (range 8–61). During or after paracetamol therapy the median serum levels of alanine aminotransferase and gamma glutamyl transferase were 7 U/l (range 5–15) and 52 U/l (range 26–140), respectively.

Conclusions To our knowledge we are the first to report on paracetamol intravenously in preterm infants. The highest paracetamol concentration (64 mg/l) was far below 150 mg/l, which is reported as the toxic value in children. During paracetamol therapy we found no indications of liver failure. This case series of preterm infants with a gestational age below 32 weeks indicates that paracetamol intravenously with a maintenance dose of 15 mg/kg per day is well tolerated while achieving an adequate analgesic effect.