The Rehabilitation of Chronic, Drug Resistant Cases of Tuberculosis with Cycloserine, and Successful Treatment of Virgin Cases

1. Data are presented on 397 cases of tuberculosis treated with cycloserine (CS) alone, or in combination with INH. The original purpose of combining CS and INH was to obtain a CS dose which would enhance the antituberculosis effects of INH, while keeping the toxicity at a minimum.

2. Our data show that the therapeutic efficacy of CS, alone or combined with INH, depends upon the attainment and maintenance of CS plasma levels above 20 mcg./ml.

3. The toxicity of CS has been reduced,

a) by the concomitant administration of pyridoxine hydrochloride, which also protects against INH in combination therapy;

b) by spreading the daily dose as widely as possible, and

c) by insuring that the plasma levels of CS are kept well below 50 mcg./ml.

Under this regimen, very few cases had to be discontinued because of toxicity.

4. Cycloserine alone in doses which maintain the plasma level at about 30 mcg./ml. has been shown to induce prompt clinical and roentgenographic improvement, a gain in weight, and rapid reversal of infectiousness, in a large proportion of both resistant and virgin cases of tuberculosis.

5. Bacillary resistance to CS developed but rarely, and in our experience has never been complete, even after continuous administration over several years.