1969 Volume 17 Issue 2 Pages 149-154
1) In the susceptibility test of 60 strains of Staphylococcus aureus isolated from patients using plate dilution method, 24 strains were inhibited by 1. 6 mcg/ml of doxycycline and 57 strains by 50 mcg/ml. Doxycycline was found to be more active for the strains resistant to tetracycline and demethylchlortetracycline. These tetracyclines were found to have cross-resistance with each other.
2) In absorption and excretion study in human subjects, following 200 mg oral administration a sustained blood level and low urinary output (15 % of dose in 24 hours) were observed. Cup plate method produced lower values than those with vertical method in the determination of blood concentration.
3) Urinary and biliary excretion and distribution study following 5 mg/kg intravasal dose in dogs were carried out. Biliary excretion was much less than urinary excretion. Values calculated from the study are as follows: half-life 7. 0 hours, renal and biliary clearance 1. 1 and 0. 01 ml/min/kg, volume of distribution 2. 0 L/kg, and rates of removal from kidney and bile 3 96 and 0. 04 % respectively. The data seems to indicate a slower removal a ndjor inactivation of doxycycline in b ody tissue.
4) In protein binding study with bovine serum, the binding rate of doxycycline, tetrac ycline and demethylchlortetracyclinew ere found to be 40-31 %, 30-25 % and 38-35 % respectively.
5) The study on the chelating action of tetracyclinesw ith Ca++, M g++, F e++, Fe+++ and Al+++ ons were carried out. The activity of doxycycline seems to be less influenced by these metals than other tetracyclines.
6) In clinical observation of 31 cases with respiratory and other infections, treatment with doxycycline (initial 200 mg, successive 100 mg daily dose in most of patients) showed excellent or good results for 23 cases, fair for 5, and poor for 3. The side-effects of 2 cases with nausea and 2 cases with anorexia were observed.
