Oral preparation comprising specific organic acid, and method for improvement in elution property and chemical stability of oral preparation

摘要

Disclosed is a chemically stable oral preparation having an excellent elution property, which comprises a specific morphinan derivative or a pharmacologically acceptable acid addition salt thereof as an active ingredient. Specifically disclosed is an oral preparation which comprises a specific morphinan derivative or a pharmacologically acceptable acid addition salt thereof as an active ingredient, and additionally contains such an organic acid that 30 mL or more of water is needed for dissolving 1 g of the organic acid at 20˚C. Also disclosed is a method for improving the elution property and the chemical stability of an oral preparation comprising a specific morphinan derivative or a pharmacologically acceptable acid addition salt thereof as an active ingredient, which comprises adding such an organic acid that 30 mL or more of water is needed for dissolving 1 g of the organic acid at 20˚C to the oral preparation.