[Drug interactions of phenylbutazone and phenprocoumon in a warmblood gelding].

The research paper discusses a case where a horse developed severe coagulation disorders due to the simultaneous administration of the drugs phenprocoumone and phenylbutazone, resulting in its death. The authors caution against combining these two drugs due to the elevated risk of bleeding.

Case Description

• A 15-year-old Oldenburger gelding was treated for laminitis for three weeks with phenprocoumone (an anticoagulant, administered once daily) and phenylbutazone (administered twice daily).
• Post-treatment, it was brought to the Equine Clinic University of Zurich with acute colic and advanced symptoms of shock.

Diagnosis and Outcome

• The horse was diagnosed with a combined drug-induced coagulopathy, a condition that interferes with blood clotting, on the basis of clinical signs and lab values.
• Vitamin-K1, the antidote for phenprocoumone toxicity, was administered, but the horse’s condition continued to deteriorate and it was euthanized.
• A subsequent necropsy examination revealed extensive, multifocal bleeding on the serosal surface of the viscera and into the visceral cavities.

Research Findings and Implications

• The study implies that the concurrent administration of phenprocoumone and phenylbutazone resulted in a drug interaction that intensified the anticoagulant effect of the phenprocoumone.
• As a result of this case, the authors recommend that the concurrent use of phenprocoumone (a coumarin derivative) and phenylbutazone should be avoided due to the increased risk of severe bleeding.
• The authors also stress the importance of regular monitoring and continuous evaluation of coagulation status when horses are being treated with anticoagulant medications, and the necessity of being alert to possible drug interactions.