Tinidazole Rifampicin

Rifampicin modestly increases the clearance of metronidazole and tinidazole but the clinical importance of this is uncertain. 

After 6 healthy subjects took rifampicin 600 mg daily for 7 days the peak serum levels of a single 600-mg dose of tinidazole were reduced by 22%, the AUCo 24 was reduced by 30% and the half-life was reduced by 27% (from 7.66 to 5.6 hours). ... 

This interaction almost certainly occurs because rifampicin (a well-recognised and potent enzyme inducer) increases the metabolism of metronidazole and tinidazole by the liver. 

The clinical significance of these interactions appear not to have been studied. A 30% reduction in metronidazole levels would not be expected to be of much clinical significance and there do not appear to be any reports of an interaction in practice. Rifampicin is known to act synergisti-cally with metronidazole, so it may be that any reduction in levels is offset by enhanced antimicrobial activity. Tinidazole acts very much like metronidazole, and therefore a clinically significant interaction between rifampicin and either of these drugs seems unlikely. 

Patel RB, Shah GF, Raval JD, Gandhi TP, Gilbert RN. The effect of cimetidine and rifampicin on tinidazole kinetics in healfhy human volunteeiB. Indian Drugs (1986) 23,338-41. 

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