Patients with
silicotuberculosis have been reported to respond poorly to antituberculosis
chemotherapy. Therefore, in a study in Hong Kong, 240 Chinese male patients with both
silicosis and
pulmonary tuberculosis were all prescribed treatment three times weekly with
streptomycin,
isoniazid,
rifampin, and
pyrazinamide, allocated at random to be given for a total duration of either 6 (M6 regimen) or 8 months (M8 regimen) in a concurrent comparison. Those with a history of previous antituberculosis
chemotherapy received
ethambutol as well for the first 3 months. The intake in the M6 regimen was terminated when preliminary results showed that it was inadequate, and a further 53 patients were assigned to the M8 series. Of 91 assessable patients in the concurrent comparison with susceptible strains pretreatment, 44% were culture negative at 1 month, 80% at 2 months, and 98% at 3 months, and 1 had an unfavorable bacteriologic response during
chemotherapy. During 3 yr of assessment, bacteriologic relapse after
chemotherapy occurred in 22% of the M6 compared with 7% of the M8 patients (p less than 0.025, log-rank test). Inadequate
chemotherapy was received by 12% of the 240 patients in the concurrent comparison because of default and by 22% because of adverse effects, but by 3 yr 92% of patients with susceptible strains pretreatment in each series had a favorable status following
retreatment for relapse or for initially inadequate
chemotherapy when required. The results show that patients with
silicosis require at least 8 months of treatment.