Laquinimod-stable preparations

A procedure for validating a batch of a pharmaceutical product containing N-ethyl-N-phenyl-1,2-dihydro-4-hydroxy-5-chloro-1-methyl-2-oxoquinolin-3-carboxamide or one of its salts and a pharmaceutically acceptable vehicle for distribution, comprising a) subjecting a sample of the batch to a stability test; b) determine the total amount of an oxidation decomposition product in the batch sample after the stability test; and c) validate the batch for distribution only if the sample of the batch after the stability test does not contain more than a total of 0.5% w / w with respect to N-ethyl-N-phenyl-1,2-dihydro-4 -hydroxy-5-chloro-1-methyl-2-oxoquinolin-3-carboxamide, from the oxidation decomposition products of N-ethyl-N-phenyl-1,2-dihydro-4-hydroxy-5-chloro- 1-methyl-2-oxoquinolin-3-carboxamide.