Beef cattle were given a single dose (1 mg/kg bw) of diphenadione. Blood extracted from these cows proved toxic to vampire bats (Desmodus rotundus) and remained toxic for 3 days without harming the cattle. Cattle treated this way experienced a 93 % reduction in vampire bat bites. Bioassays of the milk and liver from these cattle indicated that there was no residual diphenadione.

Rat livers were homogenized in 0.25 M sucrose, 0.05 M potassium phosphate buffer, pH 7.5. Dithiothreitol was added to a final concentration of 0.5 mM. Nitrogen gas was bubbled through the homogenate for 3 minutes in order to inhibit the epoxidation of [3H]vitamin-K1. The epoxidation reaction was initiated by addition of 3 micro-g of [3H]epoxide and incubated for 30 min at 37 deg-C. The reaction was terminated by adding 7 mL of isopropanol-hexane (3:2). After centrifugation, the hexane layer was chromatographed by thin-layer chromatography. Diphenandione demonstrated a 90% inhibition of vitamin K1 epoxide reductase at a concentration of 50 microM.