The perioperative administration of selective cyclooxygenase-2 (COX-2)-inhibitors to avoid postoperative pain is an attractive option: they show favorable gastro-intestinal tolerability, lack inhibition of blood coagulation, and carry a low risk of asthmatic attacks. The purpose of this study was to determine the cerebrospinal fluid (CSF), plasma, and tissue pharmacokinetics of orally administered etoricoxib and to compare it with effect data, i.e., COX-2-inhibition in patients after hip surgery. The study was performed in a blinded, randomized, parallel group design. A total of 12 adult patients were included who received 120 mg etoricoxib (n=8) or placebo (n=4) on day 1 post-surgery. Samples from plasma, CSF, and tissue exudates were collected over a period of 24 h post-dosing and analyzed for etoricoxib and prostaglandin E₂ (PGE₂) using liquid chromatography-tandem mass spectrometry and immuno-assay techniques. CSF area under the curve (AUC) [AUCs_(O-24h)] for etoricoxib amounted to about 5% of the total AUC in plasma (range: 2-7%). Individual CSF lag times with respect to (50%) peak plasma concentration were ≤2 h in all but one case (median: 1 h). PGE ₂ production in tissue was significantly blocked by the COX-2 inhibitor starting with the appearance of etoricoxib in tissue and lasting for the whole observation period of 24 h (P<0.01). In conclusion, etoricoxib reaches the CSF and site of surgery at effective concentrations and reduces PGE₂ production at the presumed site of action.