Demethylchlortetracycline and Tetracycline. A Critical Comparison: in vitro Activity, Serum Concentrations, and Effect of Serum Binding.

In September, 1959, a new tetracycline compound, demethylchlortetracycline * (here-after referred to as DMCT), became available for general use. This compound is reported to be identical in structure to chlortetracycline except for the absence of a methyl group in the 6-position. 1 In early studies it was found to be more resistant to acid and alkali degradation than the other tetracyclines in common use, 1 and to be generally more active against bacterial pathogens than tetracycline (hereafter referred to as TC) or oxytetracycline. 2-5 The amount of DMCT absorbed from the gastrointestinal tract of man following a single dose was less than with TC, 6,11 but Kunin and Finland found that the serum half-life was 44% greater for DMCT than for TC, and the renal clearance of the former drug was only 43% of the latter. 7 Assays of serum antibacterial activity after equal doses of the 2 drugs showed significantly