Phenprocoumon Flurbiprofen

Probe drugs used for CYP2C9 phenotyping are tolbutamide, S-warfarin, phenytoin and losartan. Diclofenac, flurbiprofen, phenprocoumone and torasemide have also been used. For safety concerns, the current preferred probe is tolbutamide, despite some risk of hypoglycemia. 

Marbet GA, Duckert F, Walter M, Six P, Airenne H. Interaction study between phenprocoumon and flurbiprofen. Curr Med Res Opin 1977 5(1) 26-31. 

A small but significant fall in Quick value (from 23.84 and 25.05% to 20.68 and 20.29%) occurred in 19 patients stabilised on phenprocoumon when they were given flurbiprofen 50 mg three times daily for 2 weeks. Two patients bled (haematuria, epistaxis, haemorrhoidal bleeding) and the prothromhin times of 3 patients fell helowthe therapeutic range. ... 

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