ABSORPTION AND METABOLISM OF DEXTRORPHAN AND DEXTROMETHORPHAN ADMINISTERED VIA THE NASAL ROUTE IN THE GUINEA-PIG

Dextromethorphan is a widely used non-narcotic antitussive agent. Foll owing oral administration, dextromethorphan is rapidly metabolised, wi th wide interindividual variations. The pharmacokinetic profiles of de xtromethorphan and its metabolite dextrorphan administered via the nas al route were investigated in this study in the anaesthetised guinea-p ig. The results show that the metabolic pathway of dextromethorphan an d dextrorphan administered via the nasal route presents the same metab olites as with oral administration. Dextromethorphan is rapidly and ex tensively metabolised to dextrorphan, reaching the same plasma concent rations as dextrorphan administered directly by the nasal route. This metabolite might therefore be used directly in therapy.