A controlled trial of daily and intermittent rifampicin plus ethambutol in the retreatment of patients with pulmonary tuberculosis: results up to 30 months.

In a controlled clinical trial in Hong Kong, 575 Chinese adults with smear-positive isoniazid-resistant pulmonary tuberculosis, who had previously been treated with first-line chemotherapy, were allocated at random to regimens of rifampicin plus ethambutol daily (ER7), twice-weekly (ER2), once-weekly (ER1), or daily for 2 months and then once-weekly (ER7ER1), or to a standard retreatment regimen of daily ethionamide plus pyrazinamide plus cycloserine (EtZC). The ER7 patients were allocated to 12 or 18 months of chemotherapy, and the remainder to 18 months. As assessed at 18 months, a favourable response was achieved in 87 per cent of 91 ER7 patients, 79 per cent of 84 ER2, 81 per cent of 53 ER1, 87 per cent of 62 ER7ER1, and in 88 per cent of 68 EtZC patients (93 per cent of 59 EtZC patients if those with ethionamide-resistant strains pretreatment are excluded). As assessed at 18 and 30 months the ER7 regime was as effective as the control EtZC regimen, and 18 months of chemotherapy on the ER7 regimen conferred no benefit over 12 months. No patient on either regimen relapsed after 18 months. Adverse reactions were uncommon on the daily rifampicin regimen but relatively common on the intermittent and control regimens. The commonest reaction to the intermittent regimens was the 'flu' syndrome, which was associated with the presence of circulating rifampicin-dependent antibodies (P less than 0-001).