THE CONTROL OF EXPERIMENTAL PNEUMONIA WITH PENICILLIN

III. Inhalation Therapy of Established Pneumonia, as Related to Blood and Lung Levels

¹ Medical Division, Army Chemical Center, Maryland and Johns Hopkins University Medical School, Baltimore, Maryland

In pneumococcal pneumonia of rats, untreated for 24 hours, 4 intramuscular injections of 250 and 500 units of penicillin reduced mortality from 94 per cent observed in controls, to 49 and 41 per cent, respectively. With 4 inhalations of a mist containing 400 units of penicillin per liter of air the mortality was 21 per cent. The difference between the mortality rates after aerosolization and after intramuscular injection is statistically significant.

Initial blood levels of penicillin in pneumonic rats were higher following intramuscular injection than after exposure to aerosol, but levels were better maintained in aerosol treated animals. Normal rats exposed to the same penicillin aerosol had blood levels 3 times as high as rats with pneumonia of 24 hours duration.

Penicillin levels in the respiratory tract of pneumonic rats following aerosolization were more than 25 times as high as levels in rats treated by intramuscular injection. Normal rats exposed to the same penicillin aerosol had lung levels 3 times as high as pneumonic rats. After exposure of rats to this particular aerosol only a small fraction of the penicillin retained was in the trachea; the largest portion was in the structures distal to the carina. In pneumonic rats exposed to aerosol there was only a trace of penicillin in the consolidated portions of the lung.