S-6436, a new long-acting preparation of cephalexin (CEX), was studied both basically and clinically in the urological field and the results obtained were as follows:
1. In vitro antibacterial activity
MICs of CEX against clinically isolated 73 strains of E. coli were distriblited among ≤0.2≥100μg/ml with inoculum size of 108 cells/ml but the majority of MICs was ≥100μg/ml. On the other hand, with inoculum size of 106 cells/ml a peak of MIC distribution was 3.12μg/ml.
MICs of CEX against clinically isolated 15 strains of Klebsiella pneumoniae were distributed among 50-≥100μg/ml mostly ≥100μg/ml, with inoculum size of 108 cells/ml but with 106 cells/ml a peak was 3.12μg/ml.
MICs of CEX against clinically isolated 95 strains of Serratia marcescens and 18 strains of Pseudomonasaeruginosa were mostly ≥100μg/ml with both inoculum sizes of 108 and 106 cells/ml.
2. Serum level
Three healthy adult volunteers were orally administered S-6436 at a single dose of 500mg after usual meal. Mean peak serum concentration of S-6436 was appeared at five hours with 6.8μg/ml and effective serum levels continued for approximately five hours. Accordingly it is considered that therapeutic efficacy of S-6436 can be expected at a dose of 500mg b.i.d.
3. Urinary recovery
The urinary recovery of S-6436 for twelve hours was 83.1% on an average following an administration of a single dose of 500mg.
4. Clinical result
S-6436 was administered to the majority of 20 cases with urinary tract infections at a dose of 500mg b.i.d., and the clinical effects obtained were excellent in 15 cases, good in 3 cases and poor in 2 cases, effective ratio being 90%. In 13 cases with simple urinary tract infections, the effective ratio was 92% and in 7 cases with complicated urinary tract infections, the effective ratio was 86%.
5. Adverse reaction
In S-6436 administered 20 cases, no adverse reactions were complained. These results indicated that S-6436 was equal to CEX in the effectiveness and safety in the therapy of urinary tract infection. Accordingly it is considered that S-6436 500mg b.i.d. is more acceptable and more convenient for patients than CEX 250mg q.i.d.
