Antibacterial activity of serum after oral doses of tetracycline, demethylchlortetracycline, and 6‐methyleneoxytetracycline

Studies in man indicate that tetracycline and 6‐methyleneoxytetracycline are absorbed more rapidly after oral administration than demethylchlortetracycline but that the antibacterial activity of the last is longer lasting. After 500 mg. of tetracycline and 300 mg. of the others, the amount in the blood stream is proportional to the dose; but when compared in terms of activity against Bacillus cereus, the effects of tetracycline are distinctly inferior to those of the other two, while the average antistreptococcal activity after demethylchlortetracycline is about the same as that after tetracycline and slightly greater than that after 6‐methyleneoxytetracycline. Plasma protein binding is about the same for demethylchlortetracycline and 6‐methyleneoxytetracycline but much less for tetracycline.