The present study assesses the bioavailability of Ofloxacin (O)
following single oral administration of the drug along with Rifampicin
(R), or Isoniazid (H), or Pyrazinamide (Z) or a combination of three
drugs. Information on the pharmacokinetics of O in the presence of R,
H and Z based on the blood concentrations upto 8 hours, on the
proportions of the doses of the drugs and their metabolites excreted in
urine upto 8 hours and also the effect of O on the other antituberculosis
(TB) drugs in terms of absorption and interactions are
extensively studied. The bioavailability indices of these drugs are
assessed. The investigation was undertaken in a total of 12 male
healthy volunteers and each volunteer was investigated on four
different occasions at weekly intervals. A partially balanced incomplete
block design was employed and the allocation of O or the drug
combinations was at random. Plasma concentrations of O, R, H and Z
were determined. Urinary excretion of these drugs, together with their
primary metabolites was also determined. Various pharmacokinetic
parameters were calculated. The results have shown that the
bioavailability of O is not impaired when administered with other antituberculosis
drugs like R, H and Z and does not exercise any
therapeutic penalty. The bioavailability of other anti-TB drugs like R, H
and Z does not get affected when administered along with O. Human
bioavailability studies, in general, provide direct straightforward
information on the degree of absorption and biotransformation of
drugs. The results of the present study indicate that the
pharmacokinetic properties of O, R, H and Z as assessed after
individual and combined administration of these drugs do not get
affected or altered. Since there are no interactions among these drugs,
the use of 0 in the treatment of pulmonary tuberculosis is justified