Tri-minocycline: a minocycline complex for parenteral use. I. Antibacterial activity and toxicity data

Aqueous solutions of tri-minocycline (equivalent to 20--50 mg/ml minocycline HCl) and preconstituted ready-for-use injections were prepared at the pH of blood; these exert high antibiotic activities equal to those of the parent substance. The chloroform/water distribution coefficients of tri-minocycline in the different types of injections were somewhat lower, but in the same order of magnitude as that of the parent substance. The MIC values of tri-minocycline proved to be very low and the LD50 values very high, their separation covering more than 3 orders of magnitude.