phenprocoumon
... that taking St John's wort can weaken the effects of the blood thinner phenprocoumon?
... that taking <a href="./Hypericum_perforatum" id="mwBrg" rel="mw:WikiLink" title="Hypericum perforatum">St<span id="mwBrk" typeof="mw:Entity"> </span>John's wort</a> can weaken the effects of the <a href="./Anticoagulant" id="mwBro" rel="mw:WikiLink" title="Anticoagulant">blood thinner</a> <b id="mwBrs"><a href="./Phenprocoumon" id="mwBrw" rel="mw:WikiLink" title="Phenprocoumon">phenprocoumon</a></b>?