Drug interactions in the horse: effect of furosemide on plasma and urinary levels of phenylbutazone
Roberts, B.L.; Blake, J.W.; Tobin, T.
Research Communications in Chemical Pathology and Pharmacology 15(2): 257-265
1976
ISSN/ISBN: 0034-5164 PMID: 981785 Document Number: 105210
Horses pretreated with 6.6 mg/kg of phenylbutazone were injected with 1 mg/kg of furosemide intravenously. Furosemide had no clinically significant effect on either plasma levels or plasma half-life of phenylbutazone. Furosemide reduced urinary levels of phenylbutazone 18-fold to concentrations which may result in inconsistent drug detection in routine screening tests. The results show that it is not possible to monitor compliance with phenylbutazone medication rules by means of urinalysis alone if the use of furosemide is permitted. Furosemide treatment, however, does not interfere with monitoring by plasma level determinations.