Isoniazid therapy and monitoring plasma levels

: Plasma levels of isoniazid (INH) have been monitored in fifteen children, aged 1 to 13 years, who were under chronic therapy with INH plus rifampin for tuberculosis. The pharmacokinetic parameters of children were not significantly different from those found in adults by other authors. It is necessary to check two plasma concentrations at the 3rd h. versus different doses (5 mg/kg and 10 mg/kg) of INH, in order to determine the optimal dose to be given. In subjects with external ventricular drainage, the concentrations of INH in cerebro-spinal fluid are lower than in plasma. The latter finding should be stressed for its importance in the therapy of tuberculous meningitis.