Inactivation of isoniazid by condensation in a syrup preparation

This paper reports the gross and rapid condensation of isoniazid in a commercial black-currant-flavoured syrup. In vitro studies showed that the condensation was due, at least partly, to the glucose contained in the syrup, paper chromatography having demonstrated the presence of D(+)-glucose isonicotinoyl hydrazone. Controlled studies in human beings showed that the absorption of isoniazid from the preparation was considerably impaired by this condensation.It is concluded that sugars such as glucose, fructose, and sucrose-especially glucose-should not be used in isoniazid syrup preparations, and it is suggested that sorbitol, a stable non-carbonyl compound, might be a suitable substitute.