A pharmaceutical composition of anti-tubercular drugs for oral use comprising Rifampicin and/or Isoniazid wherein the bioavailability of Rifampicin and/or other drugs is enhanced. Preferably the bioavailability of Rifampicin is enhanced by preventing its degradation caused by presence of Isoniazid. Rifampicin and/or Isoniazid may be present in delayed release and/or extended release form such that minimal amount of the drug is dissolved between pH 1 and 4. preferably delayed release of Rifampicin and/or Isoniazid is achieved by treating the drugs with pH sensitive polymers.