BASIC STUDIES ON DEPOSITION OF DOXYCYCLINE IN HARD TISSUE

Abstract

The tetracyclines are said to combine with the bivalent metal ions and deposit on the growing hard. tissues such as the bone and tooth. The authors observed the influence of the antibiotic a, 6-deoxyoxytetracycline, newly developed by Pfizer, on the hard tissue histologically by fluorescence microscope and also conducted absorption tests using synthetic hydroxyapatite, obtaining the following results:
1) When 20 mg/kg of a tetracycline antibiotic were injected into the Wister strain rat intraperit oneally once a day for 60 days, fluorescence was observed in the tooth and bone in the doxycycline group of animals as in the tetracycline group. A stripe pattern in the dentine showing the interval between administrations was observed, but in the doxycycline group the width of the fluorescence seemed to be somewhat wider.
2) Also in the group of pregnant rats and mother rats in the lactation period administered with doxycycline, fluorescence was observed in the tooth and bone of the embryo and the infant. Thus, it seems that doxycycline seems to have an influence on the hard tissue of the embryo and infant.
3) The result of measuring the absorption rate in vitro of synthetic hydroxyapatite and tetracycline antibiotic using Hitachi's ultraviolet ray absorption apparatus showed 55 % for tetracycline, 58 for oxytetracycline, 62 96 for methacycline and 37 % for doxycycline, doxycycline showing the lowest rate. Although the in vitro results can not be always applied in vivo, it may be said, that the deposition of doxycycline on the tooth and bone would be small compared to the other tetracyclines.