Impact of enantiomer-specific changes in pharmacokinetics between infants and adults on the target concentration of racemic ketorolac: A pooled analysis

Br J Clin Pharmacol. 2021 Mar;87(3):1443-1454. doi: 10.1111/bcp.14547. Epub 2020 Oct 9.


Aims: Ketorolac is a nonsteroidal anti-inflammatory racemic drug with analgesic effects only attributed to its S-enantiomer. The aim of this study is to quantify enantiomer-specific maturational pharmacokinetics (PK) of ketorolac and investigate if the contribution of both enantiomers to the total ketorolac concentration remains equal between infants and adults or if a change in target racemic concentration should be considered when applied to infants.

Methods: Data were pooled from 5 different studies in adults, children and infants, with 1020 plasma concentrations following single intravenous ketorolac administration. An allometry-based enantiomer-specific population PK model was developed with NONMEM 7.3. Simulations were performed in typical adults and infants to investigate differences in S- and R-ketorolac exposure.

Results: S- and R-ketorolac PK were best described with a 3- and a 2-compartment model, respectively. The allometry-based PK parameters accounted for changes between populations. No maturation function of ketorolac clearance could be identified. All model parameters were estimated with adequate precision (relative standard error <50%). Single dose simulations showed that a previously established analgesic concentration at half maximal effect in adults of 0.37 mg/L, had a mean S-ketorolac concentration of 0.057 mg/L, but a mean S-ketorolac concentration of 0.046 mg/L in infants. To match the effective adult S-ketorolac-concentration (0.057 mg/L) in typical infants, the EC50-racemic should be increased to 0.41 mg/L.

Conclusion: Enantiomer-specific changes in ketorolac PK yield different concentrations and S- and R-ketorolac ratios between infants and adults at identical racemic concentrations. These PK findings should be considered when studies on maturational pharmacodynamics are considered.

Keywords: adults; analgesia; ketorolac; paediatrics; population pharmacokinetics.

Publication types

  • Meta-Analysis

MeSH terms

  • Adult
  • Anti-Inflammatory Agents, Non-Steroidal
  • Child
  • Humans
  • Infant
  • Ketorolac Tromethamine
  • Ketorolac*
  • Pharmaceutical Preparations*
  • Stereoisomerism


  • Anti-Inflammatory Agents, Non-Steroidal
  • Pharmaceutical Preparations
  • Ketorolac Tromethamine
  • Ketorolac