Salivary levels of isoniazid and rifampicin in tuberculous patients

Concentrations of isoniazid and rifampicin were determined in time-matched samples of saliva and serum from 30 tuberculous patients (18 with pulmonary tuberculosis and 12 with intestinal tuberculosis), comprising 18 slow and 12 rapid acetylators of isoniazid, following administration of isoniazid 300 mg and rifampicin 12 mg/kg. The diffusion of isoniazid into saliva was quite rapid and the salivary concentrations were similar to those in serum, suggesting that saliva could be used in place of serum for all pharmacokinetic studies with isoniazid. The salivary concentrations of rifampicin were much lower than those in serum, the mean peak concentrations being 0.9 and 8.5 pg/mI, respectively. Further, there was evidence of a significant delay in the diffusion of rifampicin from serum to saliva