Stereospecific pharmacokinetics of free and proteinbound ketoprofen in serum and synovial fluid of horses after intravenous and intramuscular administration

Palle Brink From the Department of Large Animal Surgery and Medicine, College of Veterinary Medicine (Brink, DeGraves, Duran), and the Department of Pharmacal Sciences, School of Pharmacy (Ravis, Campbell), Auburn University, AL 36849-5503, and the Department of Large Animal Reproduction (Johansen), Royal Veterinary University, Bülowsvej 13, DK-1870 Frederiksberg C, Denmark.

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Fred DeGraves From the Department of Large Animal Surgery and Medicine, College of Veterinary Medicine (Brink, DeGraves, Duran), and the Department of Pharmacal Sciences, School of Pharmacy (Ravis, Campbell), Auburn University, AL 36849-5503, and the Department of Large Animal Reproduction (Johansen), Royal Veterinary University, Bülowsvej 13, DK-1870 Frederiksberg C, Denmark.

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William R. Ravis From the Department of Large Animal Surgery and Medicine, College of Veterinary Medicine (Brink, DeGraves, Duran), and the Department of Pharmacal Sciences, School of Pharmacy (Ravis, Campbell), Auburn University, AL 36849-5503, and the Department of Large Animal Reproduction (Johansen), Royal Veterinary University, Bülowsvej 13, DK-1870 Frederiksberg C, Denmark.

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Dorte Johansen From the Department of Large Animal Surgery and Medicine, College of Veterinary Medicine (Brink, DeGraves, Duran), and the Department of Pharmacal Sciences, School of Pharmacy (Ravis, Campbell), Auburn University, AL 36849-5503, and the Department of Large Animal Reproduction (Johansen), Royal Veterinary University, Bülowsvej 13, DK-1870 Frederiksberg C, Denmark.

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Jennifer D. Campbell From the Department of Large Animal Surgery and Medicine, College of Veterinary Medicine (Brink, DeGraves, Duran), and the Department of Pharmacal Sciences, School of Pharmacy (Ravis, Campbell), Auburn University, AL 36849-5503, and the Department of Large Animal Reproduction (Johansen), Royal Veterinary University, Bülowsvej 13, DK-1870 Frederiksberg C, Denmark.

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Sue H. Duran From the Department of Large Animal Surgery and Medicine, College of Veterinary Medicine (Brink, DeGraves, Duran), and the Department of Pharmacal Sciences, School of Pharmacy (Ravis, Campbell), Auburn University, AL 36849-5503, and the Department of Large Animal Reproduction (Johansen), Royal Veterinary University, Bülowsvej 13, DK-1870 Frederiksberg C, Denmark.

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Abstract

Objective

To determine intravascular and intrasynovial pharmacokinetics of the R and S enantiomers of ketoprofen after IV and IM administration to horses.

Animals

6 healthy adult mares.

Procedure

Horses were weighed and ketoprofen (2.2 mg/kg of body weight) was administered IV. Blood and synovial fluid samples were obtained and analyzed for concentrations of the R and S enantiomers by means of a modified reverse-phase stereospecific high-pressure liquid chromatographic method. Three weeks later, the procedure was repeated, except that ketoprofen was given IM. Protein binding of ketoprofen enantiomers was determined by means of ultrafiltration. Nonlinear least squares methods were used to calculate pharmacokinetic parameters.

Results

Data obtained after IV administration best fit an open, two-compartment model. Mean ± SD S-to-R serum concentration ratios after IV and IM administration were 1.36 ± 0.214 and 1.34 ± 0.245, respectively. Intrasynovial concentrations of the R and S enantiomers of ketoprofen could be measured for only the first 3 hours after IV administration; concentrations were less than the limit of quantification by 4 hours after IV administration and at all times after IM administration. Extent of protein binding of the R enantiomer was not significantly different from extent of protein binding of the S enantiomer; extent of protein binding did not appear to be concentration dependent. Mean free S-to-free R serum concentration ratios, adjusted for protein binding, after IV and IM administration were 1.58 and 1.56, respectively.

Conclusions

The R and S enantiomers of ketoprofen are rapidly absorbed and eliminated, have low volumes of distribution, and are highly protein bound. (Am J Vet Res 1998;59:739-743)

Abstract

Objective

To determine intravascular and intrasynovial pharmacokinetics of the R and S enantiomers of ketoprofen after IV and IM administration to horses.

Animals

6 healthy adult mares.

Procedure

Horses were weighed and ketoprofen (2.2 mg/kg of body weight) was administered IV. Blood and synovial fluid samples were obtained and analyzed for concentrations of the R and S enantiomers by means of a modified reverse-phase stereospecific high-pressure liquid chromatographic method. Three weeks later, the procedure was repeated, except that ketoprofen was given IM. Protein binding of ketoprofen enantiomers was determined by means of ultrafiltration. Nonlinear least squares methods were used to calculate pharmacokinetic parameters.

Results

Data obtained after IV administration best fit an open, two-compartment model. Mean ± SD S-to-R serum concentration ratios after IV and IM administration were 1.36 ± 0.214 and 1.34 ± 0.245, respectively. Intrasynovial concentrations of the R and S enantiomers of ketoprofen could be measured for only the first 3 hours after IV administration; concentrations were less than the limit of quantification by 4 hours after IV administration and at all times after IM administration. Extent of protein binding of the R enantiomer was not significantly different from extent of protein binding of the S enantiomer; extent of protein binding did not appear to be concentration dependent. Mean free S-to-free R serum concentration ratios, adjusted for protein binding, after IV and IM administration were 1.58 and 1.56, respectively.

Conclusions

The R and S enantiomers of ketoprofen are rapidly absorbed and eliminated, have low volumes of distribution, and are highly protein bound. (Am J Vet Res 1998;59:739-743)

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