The pharmacokinetics and cantharides-induced blister fluid levels of norfloxacin were studied after a single 400 mg oral dose. The mean maximum serum level was 1.45 mg/l and occurred 1.5 h after administration. The serum half-life of norfloxacin was found to be 3.5 h. After 24 h 27% of the administered dose was recovered in the urine as microbiologically active compound. High urine levels were found. Rapid blister fluid penetration occurred, the maximum level (occurring between 2-3 h) was about 1 mg/l. Thereafter the blister fluid level exceeded the serum level, both declining in parallel.

Two new quinoline compounds, enoxacin (600 mg) and norfloxacin (400 mg) were administered consecutively to six healthy male volunteers. The levels of the two agents were measured in serum, urine and blister fluid. The mean peak serum level of enoxacin was 3.7 mg/l and attained at a mean time of 1.9 h after administration; the mean peak serum level of norfloxacin was 1.45 mg/l at a mean time of 1.5 h. The mean serum half-lives were 6.2 h for enoxacin and 3.25 h for norfloxacin. Both agents penetrated blister fluid well and reached maximum levels of 2.9 mg/l (for enoxacin) and 1.0 mg/l (for norfloxacin). The 24 h urinary recovery of enoxacin of 61% was about twice that of norfloxacin. No adverse effects of either agent were observed. The data suggest that enoxacin might be used as a once daily dose for the treatment of urinary tract infections, but twice daily for the treatment of susceptible pathogens causing systemic (as against urinary) infections.

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