[The fundamental and clinical studies on PT-122M (doxycycline) in the otorhinolaryngological field (author's transl)].

As the results of laboratory and clinical investigation with a new tetracycline derivate, PT-122M (doxycycline) was performed with the results which may lead to the following conclusions. 1) In vitro antibacterial activity: The minimal inhibitory concentration of doxycycline (DOTC) was measured by an agar plate dilution method. The MIC of DOTC against 60 strains of coagulase-positive Staphylococcus aureus isolated from otorrhoea was distributed over a range of 0.2 approximately 1.56 mcg/ml and 12.5 approximately 50 mcg/ml. Furthermore, Escherichia coli, Proteus mirabilis and Klebsiella pneumoniae was 3.13 to 100 mcg/ml. 2) Concentration in blood: The blood level of DOTC in healthy adults who were given 100 mg of DOTC intravenous reached maximum of 1.97 mcg/ml on the average 15 minutes after injection. Even at 12 hours after intravenous injection clinically effective serum DOTC concentration of 0.47 mcg/ml was still demonstrable. 3) CLINICAL RESULTS: PT-122M (DOCT) was intravenously injected into 30 cases with typical infection in the field of otorhinolaryngology. It was excellent in 15 cases, good in 10 cases, fair in 3 cases, and poor in 2 cases. When the cases in which it was excellent and good were considered together, good results were obtained in 25 cases, a ratio of effectiveness being 83 per cent. 4) Side effect: The comparative examination of hepatic function, electrolyte and auditory acuity before and after injection showed no significant disturbance. No side effect was shown with the intravenous injection.