Comparative blood levels and metabolism of INH and an INH-matrix preparation in fast and slow inactivators.

Two groups of tuberculosis patients, phenotyped as either slow or fast inactivators of isoniazid, participated in a preliminary bioavailability study of a new INH-matrix preparation with sustained action. The absorption, excretion and metabolic patterns of the new form were compared with those of standard INH tablets in both sets of patients, using a crossover technique.The INH-matrix was more slowly absorbed by both slow and fast inctivators. When the latter were treated with 30 mg./kg. of the matrix formulation the blood levels attained were comparable with those observed in slow acetylators treated with 10 mg./kg. normal INH. Although this dose is three times that normally recommended with standard INH, blood levels remained within safe limits owing to the drug's slow release from the matrix.