A simple paper test for isoniazid in urine.
Gangadharam, P.R.J.; Narayanan Nair, C.; Subbaiah, T.V.
Indian Journal of Tuberculosis; 1962; 9; 219-223.
Tests for the presence of chemotherapeutic drugs or their metabolites in urine play an important part in the management of the treatment of tuberculosis (Dixon et al ., 1957; Fox, 1958). A previous report from this Centre (Gangadharam et al ., 1958) presents a comparison of a number of methods for detecting isoniazid in urine including the direct naphthoquinone-mercuric chloride (N-M) test (Short and Case, 1957) and also a modification of this test which employed alkaline hydrolysis to liberate isoniazid from its conjugated forms. The direct and hydrolysis N-M tests have been employed in this Centre for the past four years to control the self-administration of isoniazid used in the domiciliary treatment of pulmonary tuberculosis. The effect of irregularity in taking isoniazid as detected by these tests on the response to treatment has been reported elsewhere (Tuberculosis Chemotherapy Centre, 1960). Since this method has the disadvantage that it requires a certain amount of equipment and trained personnel, it is not suitable for routine use in all chest clinics or under field conditions.
An attempt was therefore made in this Centre to simplify the direct N-M test by incorporating the reagents in absorbent papers. Though impregnation of the paper with the pH10 buffer and naphthoquinone reagent was successful, impregnation with the aqueous solution of the mercuric chloride was unsatisfactory. In 1960, Cattaneo, Fantoli and Belasio published details of a paper test modification of the N-M test in which this difficulty was overcome by impregnating absorbent papers with a solution of mercuric chloride in either. Since then this modification has been adopted for the preparation of the test-paper developed in this Centre.
Since a lower concentration of the naphthoquinone reagent and a shorter period of exposure was used in the preparation of the test-paper developed in this Centre than described by Cattaneo et al . (1960), both the paper tests have been compared with the direct and combined N-M tests described previously (Gangadharam et al ., 1958). This paper presents the results of the comparison and of an investigation of the specificity of the paper test.
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