Intra-articular treatment of inflammatory arthritis with microsphere formulations of methotrexate: pharmacokinetics and efficacy determination in antigen-induced arthritic rabbits.
BACKGROUND
Methotrexate (MTX) encapsulated microspheres release MTX in the joint in a slow, controlled manner following intra-articular injection in healthy rabbits. The objective of this study was to determine the pharmacokinetics of MTX and to evaluate the efficacy following intra-articular treatment of MTX-loaded microspheres in an antigen-induced inflammatory arthritis rabbit model.


METHODS
Arthritis was induced in both knee joints of rabbits using ovalbumin. Rabbits were intra-articularly treated with MTX solution or MTX microspheres and plasma concentrations of MTX were determined in the first 8 h following intra-articular treatment. Rabbits were killed 14 days following treatment and histological analysis of rabbit joints was conducted to determine efficacy.


RESULTS
Arthritis was successfully induced in the joints of rabbits with the observation of histopathological features resembling rheumatoid arthritis. No significant differences were detected between MTX solution and MTX microspheres treated groups compared to phosphate buffered saline (control) animals.


CONCLUSIONS
MTX microspheres effectively delivered the drug to the intra-articular space. However, a high degree of inter-animal variability, the severity of the disease induced and insufficient length of the observation period were suggested to be possible causes for the lack of therapeutic responses to MTX-loaded microspheres treatment.
Liang
Linda S
LS
Nanomedicine Research Center, National Health Research Institutes, No. 35, Keyan Road, Zhunan Twoan 350, Miaoli County, Taiwan, ROC. lindaliang@nhri.org.tw
Salo
Paul T
PT
Hart
David A
DA
Burt
Helen M
HM
D000818:Animals; D018501:Antirheumatic Agents / Q000008:administration & dosage* / Q000493:pharmacokinetics / Q000627:therapeutic use*; D001168:Arthritis / Q000139:chemically induced / Q000188:drug therapy*; D002626:Chemistry, Pharmaceutical; D002851:Chromatography, High Pressure Liquid; D004487:Edema / Q000139:chemically induced / Q000473:pathology; D005260:Female; D006614:Hindlimb / Q000473:pathology; D007270:Injections, Intra-Articular; D007596:Joints / Q000473:pathology; D008727:Methotrexate / Q000008:administration & dosage* / Q000493:pharmacokinetics / Q000627:therapeutic use*; D008863:Microspheres; D010047:Ovalbumin / Q000276:immunology; D011817:Rabbits
D018501:Antirheumatic Agents; D010047:Ovalbumin; D008727:Methotrexate