The pharmacokinetics of the weakly protein-bound anionic compound diatrizoate in serum and synovial fluid of the horse.
OBJECTIVE
To establish a pharmacokinetic model for the model drug, sodium diatrizoate (DTZ), allowing joint disappearance kinetics to be estimated from serum appearance kinetics following intra-articular administration, and to calculate the relative joint exposure after intravenous and intra-articular DTZ administration (F(iv/IA)).


METHODS
Each of five horses received an aqueous solution of 3.9 mg/kg sodium diatrizoate both intravenously and intra-articularly separated by a one-week wash out period. Serum and synovial samples were collected over 7 h and analyzed for content of model compound using inductively coupled plasma mass spectrometry.


RESULTS
Differential equations were used for describing the transport of DTZ between the joint and the central compartment. The three-compartment lag-time model obtained demonstrates that the rate of drug appearance in the systemic circulation equals the rate of disappearance from the joint compartment. Following intravenous and intra-articular administration, an average F(iv/IA) of 0.04% (n = 4) was calculated based on the synovial fluid profiles of DTZ.


CONCLUSIONS
This study implies that aspects of the intra-articular fate of DTZ can be obtained from serum data in case synovial fluid samplings are limited, for various possible reasons. The low F(iv/IA) may stimulate future research in the field of intra-articular administration of anti-osteoarthritic drugs.
Frost
Anna Buus
AB
Department of Pharmaceutics and Analytical Chemistry, Faculty of Pharmaceutical Sciences, University of Copenhagen, Universitetsparken 2, DK-2100, Copenhagen Ø, Denmark.
Larsen
Frank
F
Larsen
Susan Weng
SW
Østergaard
Jesper
J
Thomsen
Maj Halling
MH
Stürup
Stefan
S
Andersen
Pia Haubro
PH
Larsen
Claus
C
D000818:Animals; D003973:Diatrizoate / Q000008:administration & dosage / Q000097:blood* / Q000493:pharmacokinetics*; D006736:Horses; D007270:Injections, Intra-Articular; D007275:Injections, Intravenous; D008962:Models, Theoretical; D013582:Synovial Fluid / Q000378:metabolism*; D013997:Time Factors
D003973:Diatrizoate