Pharmaceutical Applications
A semisynthetic derivative of erythromycin A, supplied for oral administration. It is stable at acid pH due to the presence of the fluorine atom at C-8 of the erythronolide A ring.
It is active against most streptococci (including Str. pneumoniae and Str. agalactiae; MIC50 0.03 mg/L), Mor. catarrhalis, N. gonorrhoeae (MIC50 0.04 mg/L), C. trachomatis (MIC 0.06– 0.125 mg/L), M. genitalium (MIC50 0.007 mg/L) and U. urealyticum (MIC50 0.03 mg/L). It has little or no activity against H. influenzae and M. hominis. Activity against anaerobes is similar to that of erythromycin A. It displays cross-resistance with erythromycin A.
A single 500 mg oral dose achieved a mean peak plasma concentration of 1.2–2 mg/L after 1–2 h. The apparent elimination half-life was 8 h and the volume of distribution 5.5 L/ kg. With repeated doses (500 mg orally every 8 h for 10 doses), plasma concentrations were 0.72 mg/L immediately before and 0.67 mg/L at 4 h after the last dose. Absorption is not significantly affected by food. After administration of a single 375 mg tablet of flurithromycin ethylsuccinate, the mean serum levels at 0.5 h were 0.43 ± 0.35 mg/L. The mean peak serum concentration (1.41 ± 0.49 mg/L) was achieved at 1 h. At 8 and 12 h, the serum levels were 0.14 (± 0.05) and 0.04 (± 0.04) mg/L, respectively. The apparent elimination half-life is 3.94 (± 1.42) h. The apparent half-life in artificial gastric juice was about 40 min.
It is generally well tolerated and has been used successfully for the treatment of lower respiratory tract infections. Availability is limited.
