The single dose pharmacokinetics of Isoniazid
(7.5 mg/kg) and Rifampicin (12 mg/kg) were
examined in 18 patients with mild or moderate
renal failure and 17 patients with severe renal
failure. The findings were compared with those in
16 healthy subjects. The renal excretion of
Isoniazid and Acetyl Isoniazid and that of
Rifampicin and Desacetyl Rifampicin was
significantly less in patients with renal failure than
in healthy subjects. The decrease was greater in
patients with severe renal failure than in those
with mild or moderate failure. The exposure
(AUC) and half-life of Isoniazid calculated on the
basis of plasm concentrations were significantly
higher in slow acetylators in both groups of
patients than in healthy subjects. The differences
between the two groups of patients were,
however, not significant. The plasma Isoniazid
concentrations among rapid acetylators and the
Rifampicin concentrations were similar in the
three groups of subjects, leading to similar
exposure and half-life values. These findings
suggest that while it is not necessary to reduce the
dosage of Isonizaid or that of Rifampicin in rapid
acetylators, it is necessary to reduce Isoniazid
dose in slow acetylators with renal failure
