[Tetracycline sorption by alveolar macrophages of rabbits at early stages of interaction]. / Dinamika sorbtsii tetratsiklinov al'veoliarnymi makrofagami krolikov na rannykh stadiiakh vzaimodeistviia.

Interaction of rabbit alveolar macrophages with morphocycline, tetracycline and methacycline was studied. The use of the membrane microfiltration technique in investigation of the antibiotic absorption by the macrophages provided description of the time course of the drug interaction with the cells at its early stages. It was shown that the macrophages mainly absorbed the tetracyclines within the first 20 seconds (1 minute incubation). Later, within the period of 1-5 minutes no significant time course was observed. The medium temperature within 4-37 degrees C and the number of the cells in the system (0.1-5 minutes no significant time course was observed. The medium temperature within 4-37 degrees C and the number of the cells in the system (0.5-1 million/ml) had no effect on the parameters of the tetracyclines sorption by the macrophages. The percentage of the decrease of the morphocycline level in the extracellular medium was stable at the drug concentration in the cells ranging within 10-50 micrograms/ml. The respective figures for tetracycline and methacycline were 10-100 and 10-5000 micrograms/ml. Further increasing of the concentration of the antibiotics in the incubation medium resulted in a significant lowering of the percentage of their binding. It was suggested that absorption of the tetracyclines by the cells was associated with their intracellular binding.

[Bioavailability of drug forms of tetracycline-group semisynthetic preparations for internal use]. / Biodostupnost' lekarstvennykh form dlia priema vnutr' polusinteticheskikh preparatov gruppy tetratsiklina.

Bioavailability of methacycline capsules manufactured by two different firms was studied and it was shown that they had statistically significant differences. Conditions for investigation of the rate of methacycline transfer from the pharmaceutical form into solution were developed with the use of a "rotating basket". Such investigations provided in vitro prediction of the drug bioavailability. The effect of additives on bioavailability of methacycline capsules was found. Study of bioavailability of doxycycline capsules manufactured by the same two firms revealed no differences.

The parenteral application of a new metacycline preparation, tri-metacycline.

Tri-metacycline, one of the new tetracycline complexes (tritetracyclines), is prepared by mere dissolution of metacycline hydrochloride in an aqueous solution of the complexing agent. In vitro and in vivo studies show a high antibiotic activity. Significantly lower MIC values were found for tri-metacycline than for the parent compound. Parenteral administration resulted in high sera and tissue values, without signs of accumulation; excretion via the kidneys was proved.

Interference of iron with the absorption of tetracyclines in man.

Ferrous sulphate administered together with tetracycline and three of its derivatives-oxytetracycline, methacycline, and doxycycline-was found seriously to impair the absorption of these antibiotics. Thus even small doses of iron taken simultaneously should be avoided during tetracycline treatment.