Cephradine levels in human aqueous humor.

In an attempt to investigate penetration of cephradine into the primary aqueous humor in man, we administered 500-mg and 1-g doses of cephradine orally to 27 patients about to undergo elective cataract extraction. A mean peak aqueous humor level of 0.87 microgram/mL was obtained at about three hours after the 500-mg dose. The mean peak aqueous humor level after the 1-g dose also occurred at three hours and was 1.99 microgram/mL, with a range from 0.91 to 3.25 microgram/mL. This concentration was greater than the median minimum inhibitory concentration (MIC) of cephradine for Streptococcus pneumoniae, Str pyogenes, and Staphylococcus aureus (when tested in nutrient agar) but was greater than the MIC for 90% of isolates only with Str pyogenes.