Cefuroxime (CXM), with its relatively broad antibacterial spectrum, good stability to beta-lactamases and high safety, has an established place in antibacterial therapy. However, like many other cephalosporins, its clinical application is rather limited due to the need for parenteral delivery. Recent work has led to the development of cefuroxime axetil (CXM-AX, SN407) which is the 1-acetoxyethyl ester of CXM is well absorbed from the gastrointestinal tract and promptly cleaved to cefuroxime thereafter. CXM-AX, in a dose of 500 mg, was given after meal by oral administration 3 times daily for 5-8 days to 10 lactating outpatients with acute mastitis. Ages of the patients ranged from 26 to 44 years, and body weights ranged from 48.0 to 59.0 kg. Clinical response was assessed as excellent in 2 cases, good in 8 cases and fair or poor in none. No adverse effects were observed. Seven strains of organisms were isolated from 7 cases. They included 5 strains of Staphylococcus aureus and 2 strains of Staphylococcus epidermidis. The MICs of CXM were under 3.13 micrograms/ml with inoculume size of 10(8) and 10(6) cells/ml. In 1 case, CXM concentrations in puruloid milk and in healthy milk were measured by bioassay with Bacillus subtilis ATCC 6633 as the test organism. The CXM concentrations in healthy milk ranged from 0.09 to 0.59 microgram/ml (mean: 0.32 +/- 0.25 microgram/ml) at 30 to 90 minutes after oral administration of 500 mg CXM-AX. The CXM concentrations in puruloid milk ranged from 0.57 to 1.05 micrograms/ml (mean: 0.74 +/- 0.27 microgram/ml).(ABSTRACT TRUNCATED AT 250 WORDS)