Fundamental studies on ceftazidime and its clinical efficacy in respiratory tract infections

Laboratory and clinical studies were carried out on ceftazidime (CAZ, SN401), a new injectable cephalosporin. As for the antibacterial activity against 324 strains of 10 species of clinical isolates, CAZ showed high activity against gram-negative bacilli, and it was far more active than cefmetazole (CMZ). When compared with ceftizoxime (CZX), CAZ was shown to be slightly less active against E. coli, K.aerogenes and P. mirabilis, but almost comparable or more active against the other strains. In particular, against P. aeruginosa, its activity was 1∼2 times higher than that of cefoperazone(CPZ) and comparable to that of gentamicin (GM) or cefsulodin (CFS). Against S. aureus, CAZ was obviously less active than CMZ or CZX and the peak of MIC of CAZ was 6. 25 jug/ml. The concentrations of CAZ in the serum and sputum were determined in 4 patients after intravenous drip infusion at the dose of 1 g. The serum concentrations immediately after drip infusion ranged from 62.5∼87μg/ml, and the mean half-life was 1.68 hours. Not less than 2 μg/ml of CAZ was recovered in sputum in 3 of the cases and the peak concentration was 4. 6 μg/ml. The clinical responses to CAZ in a total of 20 patients, 8 with pneumonia, 6 with acute exacerbation of bronchiectasis, 4 with acute exacerbation of chronic bronchitis and each 1 with infection following old pulmonary tuberculosis and organized pneumonia, were excellent in 4 cases, good in 11, fair in 2 and unassessable in 1, with the efficacy rate of 78.9%, which suggested the clinical usefulness of CAZ in respiratory tract infections. As for the side effects, rash, increase in Al-P level and decrease in WBC counts were noted in 1 case each, but all of them were only mild.