Paracetamol is an analgetic drug with additive effect if combined with indomethacin. In rat experiments, paracetamol has been shown to be gastro-protective, and in animal experiments, indomethacin blood levels decreased during combined treatment with paracetamol. The kinetic effect of paracetamol on indomethacin has been investigated in ten healthy volunteers. The mean area under the indomethacin plasma concentration curve AUC 0-alpha was 10.4 +/- 4.21 micrograms/mL x hr and did not change during combined paracetamol treatment (11.0 +/- 3.24 micrograms/mL x hr NS). Paracetamol levels were unchanged. In this study, no evidence was found that paracetamol can alter the pharmacokinetics of indomethacin in humans.