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Evaluation of the effect of cephalexin and enrofloxacin on clinical laboratory measurements of urine glucose in dogs

Christine A. Rees DVM, DACVD1 and Dawn M. Boothe DVM, PhD, DACVIM, DACVCP2
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  • 1 Department of Small Animal Medicine and Surgery, College of Veterinary Medicine, Texas A&M University, College Station, TX 77843-4474.
  • | 2 Department of Anatomy, Physiology, and Pharmacology, College of Veterinary Medicine, Auburn University, Auburn, AL 36849-5518.

Abstract

Objective—To determine the effects of cephalexin and enrofloxacin on results of 4 commercially available urine glucose tests in dogs.

Animals—6 healthy adult female dogs.

Procedure—In a crossover design, cephalexin (22 and 44 mg/kg [10 and 20 mg/lb], PO, q 8 h) or enrofloxacin (5 and 10 mg/kg [2.3 and 4.5 mg/lb], PO, q 12 h) was administered to dogs for 1 day. Urine samples were tested for glucose at 0, 6, and 24 hours after drug administration. In vitro, dextrose was added to pooled glucose-negative canine urine samples containing either no antimicrobial or known concentrations of either antimicrobial; urine samples were then tested for glucose.

Results—In vivo, false-positive results were obtained by use of a tablet test in the presence of both antimicrobials and by use of a strip test in the presence of cephalexin. In vitro, false-positive results were obtained with the tablet test at the highest urine concentration of cephalexin (2,400 μg/mL) and with a strip test at the highest concentration of enrofloxacin (600 μg/mL). Enrofloxacin in urine samples containing dextrose caused the urine glucose tests to underestimate urine glucose concentration.

Conclusions and Clinical Relevance—Cephalexin and enrofloxacin at dosages used in clinical practice may result in false-positive or false-negative urine glucose results, and care should be taken when using urine as a basis for identifying or monitoring diabetic animals. (J Am Vet Med Assoc 2004;224:1455–1458)

Abstract

Objective—To determine the effects of cephalexin and enrofloxacin on results of 4 commercially available urine glucose tests in dogs.

Animals—6 healthy adult female dogs.

Procedure—In a crossover design, cephalexin (22 and 44 mg/kg [10 and 20 mg/lb], PO, q 8 h) or enrofloxacin (5 and 10 mg/kg [2.3 and 4.5 mg/lb], PO, q 12 h) was administered to dogs for 1 day. Urine samples were tested for glucose at 0, 6, and 24 hours after drug administration. In vitro, dextrose was added to pooled glucose-negative canine urine samples containing either no antimicrobial or known concentrations of either antimicrobial; urine samples were then tested for glucose.

Results—In vivo, false-positive results were obtained by use of a tablet test in the presence of both antimicrobials and by use of a strip test in the presence of cephalexin. In vitro, false-positive results were obtained with the tablet test at the highest urine concentration of cephalexin (2,400 μg/mL) and with a strip test at the highest concentration of enrofloxacin (600 μg/mL). Enrofloxacin in urine samples containing dextrose caused the urine glucose tests to underestimate urine glucose concentration.

Conclusions and Clinical Relevance—Cephalexin and enrofloxacin at dosages used in clinical practice may result in false-positive or false-negative urine glucose results, and care should be taken when using urine as a basis for identifying or monitoring diabetic animals. (J Am Vet Med Assoc 2004;224:1455–1458)