title: Influence of exercise on the distribution of technetium Tc 99m medronate following intra-articular injection in horses.
abstract: OBJECTIVE
  To determine the effects of exercise on the distribution and pharmacokinetics of technetium Tc 99m medronate ((99m)Tc-MDP) following intra-articular (IA) injection in horses.
  
  
  METHODS
  5 horses.
  
  
  METHODS
  1 antebrachiocarpal joint (ACJ)/horse was assigned to the exercised group (n = 5), and the contralateral ACJ was evaluated in the nonexercised group (5) after a minimum washout period of 7 days. Following IA injection of (99m)Tc-MDP (148 MBq), blood and scintigraphic images of the carpus were obtained at 5, 10, 15, 20, 25, 30, 45, 60, 90, 120, 240, 360, 480, 600, 720, and 1,440 minutes. Plasma and scintigraphic radioactivity were determined over time, and pharmacokinetic parameters were generated via noncompartmental and compartmental analyses. Each horse was monitored via physical and lameness examination and ACJ synovial fluid analysis before injection and at days 1, 2, 3, and 7.
  
  
  RESULTS
  Lameness was not observed. Mean ± SD synovial fluid WBC count increased at day 1 (exercised, 721 ± 234 cells/μL; nonexercised, 948 ± 223 cells/μL), but returned to baseline at days 3 and 7 Mean time to maximum plasma radioactivity was earlier in the exercised group (16.00 ± 2.35 minutes) than the nonexercised group (43.75 ± 3.64 minutes). Linear regression of the scintigraphic radioactivity-time curves revealed a greater negative slope in the exercised group within the first 25 minutes. There was no difference in absorption or elimination rate constants in a 2-compartment model.
  
  
  CONCLUSIONS
  IA injection of (99m)Tc-MDP was safe and effective for evaluating synovial solute distribution. Exercise significantly increased early transfer of (99m)Tc-MDP from the ACJ into plasma, although absorption and elimination rate constants were not affected. Exercise may affect synovial clearance and withdrawal times of medications administered IA.
authors.affiliation: Department of Veterinary Clinical Sciences, College of Veterinary Medicine, The Ohio State University, Columbus, OH 43210, USA.
authors.forename: Jennifer A
authors.initials: JA
authors.lastname: Dulin
authors.forename: W Tod
authors.initials: WT
authors.lastname: Drost
authors.forename: Mitch A
authors.initials: MA
authors.lastname: Phelps
authors.forename: Elizabeth M
authors.initials: EM
authors.lastname: Santschi
authors.forename: Maria I
authors.initials: MI
authors.lastname: Menendez
authors.forename: Alicia L
authors.initials: AL
authors.lastname: Bertone
mesh_terms: D000818:Animals; D050824:Carpal Joints / Q000000981:diagnostic imaging / Q000378:metabolism; D002350:Carpus, Animal / Q000000981:diagnostic imaging / Q000378:metabolism; D018592:Cross-Over Studies; D005260:Female; D006734:Horse Diseases / Q000139:chemically induced / Q000175:diagnosis / Q000000981:diagnostic imaging; D006736:Horses / Q000502:physiology*; D007091:Image Processing, Computer-Assisted; D007270:Injections, Intra-Articular / Q000662:veterinary; D007794:Lameness, Animal / Q000139:chemically induced / Q000175:diagnosis / Q000000981:diagnostic imaging; D008956:Models, Chemical; D010805:Physical Conditioning, Animal; D011877:Radionuclide Imaging / Q000662:veterinary; D019275:Radiopharmaceuticals / Q000008:administration & dosage / Q000097:blood / Q000493:pharmacokinetics*; D013582:Synovial Fluid / Q000000981:diagnostic imaging / Q000378:metabolism*; D013669:Technetium Tc 99m Medronate / Q000008:administration & dosage / Q000097:blood / Q000493:pharmacokinetics*
chemical_list: D019275:Radiopharmaceuticals; D013669:Technetium Tc 99m Medronate