DETERMINATION OF IRON BY THE FERROCHEM-II - INTERFERENCE BY TUBERCULOSTATICS

Iron levels in samples from certain treated tuberculous patients are u nderestimated by the Ferrochem II analyser. Of the tuberculostatic dru gs examined for a possible interference, isoniazid, ethambutol, rifamp icin, pyrazinamide and Rifater(R) (a mixture of rifampicin, isoniazid and pyrazinamide), only pyrazinamide and Rifater(R) (due to its pyrazi namide content) were associated with iron levels differing significant ly (p < 0.001) from those of controls, with means of -317.2 and -185.6 mumol l-1 for pyrazinamide and Rifater(R) respectively as against 9.9 1 mumol l-1 for the controls. The negative interference (I) due to pyr azinamide was independent of iron level in the samples but dependent o n pyrazinamide concentration in the same (P) (r = 0.9993), I = -0.4380 P - 0.4276.