Summary
In rats, pretreatment with spironolactone, norbolethone or ethylestrenol enhances
the disappearance of bishydroxycoumarin from blood and restores prothrombin time to
almost normal whereas triamcinolone or progesterone fail to do so.
In itself SKF 525-A does not influence prothrombin time, but it markedly increases
the blood concentration and the anticoagulant activity of bishydroxycoumarin. Furthermore,
this microsomal enzyme-inhibitor suppresses the decrease of blood bishydroxycoumarin
concentration elicited by ethylestrenol.
Pretreatment with spironolactone or ethylestrenol (but not with progesterone) enhances
the NADPH-dependent enzymatic decay of bishydroxycoumarin in liver microsomal + supernatant
fraction.
The elimination of bishydroxycoumarin from blood is reduced if its administration
is followed by subsequent treatment with norbolethone, progesterone, ethylestrenol
or triamcinolone.
These findings suggest that great care should be exercised in patients on anticoagulant
therapy and treated previously or conjointly with various steroids ; in dubious cases
not only prothrombin time but also the blood concentration of the anticoagulant should
be checked.