A simple and easy method for determination of meloxicam in rat muscle and plasma

Meloxicam is a nonsteroidal anti-inflammatory drug (NSAID) which inhibits cyclooxygenase (COX), the enzyme responsible for the first step in synthesis of various prostaglandins (PGs) from arachidonic acid. COX exists as two isoforms, COX-1, which is constitutively present in almost all cells and produces PGs concerned with protection of the gastric mucosa and kidney functions, and COX-2, which is induced by cytokines or hormones in inflammatory processes [1]. Although meloxicam selectively inhibits COX2, the COX-1 isoform is also affected to some extent [2-5]. To overcome associated side effects and local disorders, we have paid attention to transdermal administration and have focused on analytical methods capable of determining drug levels in target tissues such as muscle to evaluate the pharmacokinetics of topically administrated meloxicam. To evaluate large numbers of samples, a simple and easy method would have obvious advantages. A number of approaches have been published for the determination of meloxicam in muscle, making use of radiation measurement with carbon-14-labeled meloxicam [6,7] and liquid chromatographytandem mass spectrometry [8-11]. However, these methods are unsuitable for use with large numbers of samples because they employ carbon-14-labeled meloxicam that is not commercially available. Furthermore, preparation of samples in these methods is technical and tedious because of requiring manual operations such as homogenization, solvent or solid phase extraction and evaporation and so on. Therefore, we have developed a simple and easy method for measuring meloxicam in rat muscle and plasma using a tissue solubilizer and automated column-switching high performance liquid chromatograpy (HPLC). As a tissue solubilizer, Solvable, the proprietary name for a mixture of dodecyldimethylamine oxide, secondary alcohol ethoxylate and sodium hydroxide, is used. By Original