Activity of two long-acting rifamycins, rifapentine and FCE 22807, in experimental murine tuberculosis.
The efficacy of the long-acting rifamycins, rifapentine (RPE) and FCE 22807 (FCE) in experimental murine tuberculosis was studied by counting viable bacilli in spleens. At 2 weeks after infection with Mycobacterium tuberculosis, strain H37Rv, treatment with isoniazid 25 mg/kg, rifampicin 10 mg/kg and pyrazinamide 150 mg/kg was given daily for 6 weeks. The mice were then divided into groups given RPE or FCE at intervals of 1, 2 or 3 weeks with spleen counts after 18 and 24 weeks of chemotherapy. The first experiment showed the great effect of the size of the dose of RPE, which, in once-weekly regimens, caused rapid sterilization at 16 mg/kg, less rapid sterilization at 10 mg/kg and incomplete activity at 6.25 mg/kg. Regimens of RPE given every 2 or 3 weeks were less effective, though 16 mg/kg fortnightly was as good as 6 mg/kg once-weekly. The second experiment compared RPE and FCE each given at 12 or 8 mg/kg. The results were similar though, at 8 mg/kg every 2 or 3 weeks, FCE was slightly more effective than RPE. Serum assays showed that the levels with 8 and 12 mg/kg FCE were lower than those produced even by 6.25 mg/kg RPE, suggesting that FCE would be a better drug than RPE if its bioavailability could be improved, and that the levels following 16 mg/kg RPE were similar to those found in man after 8 mg/kg RPE taken with a fat-rich meal, suggesting good prospects for effective once-fortnightly human treatment. The potential for long-acting rifamycins in the management of pulmonary tuberculosis is discussed.
Dhillon
J
J
Department of Bacteriology, Royal Postgraduate Medical School, London, UK.
Dickinson
J M
JM
Guy
J A
JA
Ng
T K
TK
Mitchison
D A
DA
D000818:Animals; D000995:Antitubercular Agents / Q000097:blood / Q000627:therapeutic use*; D004334:Drug Administration Schedule; D051379:Mice; D008807:Mice, Inbred BALB C; D009169:Mycobacterium tuberculosis / Q000302:isolation & purification; D012293:Rifampin / Q000031:analogs & derivatives* / Q000097:blood / Q000627:therapeutic use; D012294:Rifamycins / Q000097:blood / Q000627:therapeutic use*; D013154:Spleen / Q000382:microbiology; D014376:Tuberculosis / Q000097:blood / Q000188:drug therapy* / Q000382:microbiology
D000995:Antitubercular Agents; D012294:Rifamycins; C065869:FCE 22807; D012293:Rifampin; C018421:rifapentine