Background In Sweden, thiopental is used in newborns for preoperative induction and endotracheal intubation. A boy, born after 33 gestational weeks (gw), birth weight 2435 g, was prescribed thiopental 3 mg/kg before intubation. He developed a temporary hypotension and desaturation, and did not wake up as expected.

Objectives To assess thiopental pharmacokinetics in the index case and a reference group.

Methods Serum samples were obtained from the index case. Fourteen infants (27+6–42+0 gw), enrolled before surgery (median postnatal age 19.5 h; range 4–480 h), received thiopental 3 mg/kg. Seven samples were obtained for concentration assessment during 48 hours after administration.

Results In the index case, thiopental concentration was 82, 59, 42 and 32 μmol/L after 20 min, 6, 24 and 48 h respectively. In the reference group, it was 20 (median and mean) μmol/L (range 34.20–7.00) at 5 min.

Infants with a weight <3000 g had a slower decline than those >3000 g. The AUC was 18195 and 1022 min*μmol/L, and T ½ 38.5 hours and 19.5 hours for the groups, respectively.

The index case stayed unconscious and the EEG suppressed for 48 hours. Cerebral MRI at 42 gw and psychomotor development at 1.5 years were normal.

Conclusion The reference values indicate that thiopental metabolism varies in preterm infants, but that the index case had a 10-fold higher concentration than expected. The overdosage error could not be identified in the drug dilution handling. This case emphasis the importance of specially designed drug formulas for neonates.