Distribution of [14C]meloxicam in joints of rats with adjuvant arthritis

Using the new non-steroidal anti-inflammatory agent meloxicam (Mel), comparative investigations on pharmacokinetics and metabolism show good agreement between results in man and in the rat. To demonstrate preferential localization of the compound in inflamed sites, the distribution of the radiolabelled compound in arthritic joints of rats was studied using autoradiography. For that purpose an arthritis-inducing antigen was given to male albino rats. Twenty one days after antigen injection, all animals were given [14C]Mel orally. At three different times after receiving the labelled compound, the animals were sacrificed under anaesthesia. Tissue sections from each leg of each animal were taken for autoradiography. Sections were stained after film exposure using Masson-Goldner staining. The radiolabelled compound was preferentially localized in the areas which stained for inflamed connective tissue. The distribution pattern described persists beyond 24 h post-application. The figures indicate a highly efficient distribution of the radioactivity into chronically inflamed tissue of the hind foot-pads. Since negligible radioactivity was found in the front foot-pads, it is concluded that uptake into inflamed tissue is favoured.