Absence of interaction between ofloxacin and phenprocoumon

The effect of ofloxacin on steady-state phenprocoumon pharmacodynamics was investigated in 7 healthy male volunteers taking daily sub-therapeutic doses of phenprocoumon. Ofloxacin 200 mg once daily for 7 days did not alter the anti-coagulant response (Quick values) to phenprocoumon after a stabilization phase of 2 weeks. Mean Quick values during the steady-state phase before and during ofloxacin administration were 54% and 52%, respectively. In vitro studies with concentrations of 0 to 100 mg ofloxacin/1 added to plasma also failed to show any interaction. The results indicate, therefore, that ofloxacin does not interfere with vitamin K-dependent coagulation cascade, as seen after other antibiotics.