Pharmacokinetic Profile and Analgesic Activity of Chitosan-coated Ibuprofen Microemulsion Following Intravenous Administration in Rats

Intravenous ibuprofen preparations remain limited. This study assessed the analgesic efficacy and pharmacokinetics of a chitosan-coated ibuprofen microemulsion (MK). Seven groups ( n = 6; 42 rats) received oral ibuprofen (K+, 72 mg/kg), uncoated (MO) or coated (MK) microemulsion intravenously at 36 or 72 mg/kg, or one of two ibuprofen-free vehicle controls, followed by 1% acetic acid intraperitoneally 1 h later. Pain was scored by three veterinarians using the Rat Grimace Scale (RGS) and Nociceptive Behavior Score (NBS). A separate cohort ( n = 6) was profiled pharmacokinetically after MK 72 mg/kg. Interobserver reliability was high (RGS ICC[2,k] = 0.951; NBS = 0.947). Intergroup differences in cumulative AUC, the primary endpoint for both scales, were not significant (RGS p = .098; NBS p = .153). Scores tended to be lower with K+ and MK than with MO (hypothesis-generating only). Serum MK was 209.7 ± 16.8 mg/L at 5 min and 73.6 ± 11.9 mg/L at 45 min (AUC 5–45 80.2 ± 12.0 mg•h/L; apparent half-life 28.6 ± 3.3 min); concentrations fell below the quantification limit within 1–3 h, precluding terminal-phase estimates. Further preclinical evaluation is required: a head-to-head pharmacokinetic comparison of coated and uncoated microemulsions, and an adequately powered efficacy study.