Short-course chemotherapy of pulmonary tuberculosis: a new approach to drug dosage in the initial intensive phase

An analysis carried out on the dosage schemes adopted in several controlled clinical trials in tuberculosis has indicated that preestablishing the daily doses of isoniazid, rifampicin, and pyrazinamide in the initial intensive phase results in large deviations of the doses administered from those considered appropriate in mg/kg body weight. This is due partly to the variations in the patients' body weight and partly to the restrictions in terms of fine adjustments of dosage imposed by the unitary content of active principle in the available individual preparations of the drugs. The availability of a fixed-triple combination of the same 3 drugs where the content of each component is established multiplying the mg/kg requirement of each drug by 10, allows a complete coincidence between the appropriate and the administered dose simply administering 1 tablet every 10 kg of body weight. The implications of the large overdosing in light patients if the conventional approach is followed are discussed in terms of toxicity and drug purchasing cost, both being of great relevance for Third World countries where the majority of patients are of low body weight.