Metabolic fate of ulinastatin (2); Pharmacokinetics in rabbits following intra-articular administration

Flip-flop pharmacokinetics--delivering a reversal of disposition: challenges and opportunities during drug development

Flip-flop pharmacokinetics is a phenomenon often encountered with extravascularly administered drugs. Occurrence of flip-flop spans preclinical to human studies. The purpose of this article is to analyze both the pharmacokinetic interpretation errors and opportunities underlying the presence of flip-flop pharmacokinetics during drug development. Flip-flop occurs when the rate of absorption is slower than the rate of elimination. If it is not recognized, it can create difficulties in the acquisition and interpretation of pharmacokinetic parameters. When flip-flop is expected or discovered, a longer duration of sampling may be necessary in order to avoid overestimation of fraction of dose absorbed. Common culprits of flip-flop disposition are modified dosage formulations; however, formulation characteristics such as the drug chemical entities themselves or the incorporated excipients can also cause the phenomenon. Yet another contributing factor is the physiological makeup of the extravascular site of administration. In this article, these causes of flip-flop pharmacokinetics are discussed with incorporation of relevant examples and the implications for drug development outlined.

Intra-articular drug delivery systems: Overcoming the shortcomings of joint disease therapy

BACKGROUND

Intra-articular drug delivery is very useful for treating local disease flare-ups, synovitis and pain in joints. However, the effectiveness of drugs following intra-articular administration is limited by drug delivery issues.

AIM

This review addresses critical drug delivery parameters that influence the biocompatibility, tolerability and efficacy of intra-articular administrations and offers an opinion on aspects of formulation design.

METHODS

The relevant literature was reviewed, focusing on factors influencing tissue targeting, safety and effectiveness of particulate formulations.

RESULTS/CONCLUSION

Therapeutic applications of novel drug delivery systems for the localized treatment of joints have lagged significantly. Future innovations in the field will require the discovery of new therapeutic agents for regional delivery, combination regimens, novel biomaterials as drug carriers and targeting carriers to specific molecules.

Intra-articular depot formulation principles: role in the management of postoperative pain and arthritic disorders

The joint cavity constitutes a discrete anatomical compartment that allows for local drug action after intra-articular injection. Drug delivery systems providing local prolonged drug action are warranted in the management of postoperative pain and not least arthritic disorders such as osteoarthritis. The present review surveys various themes related to the accomplishment of the correct timing of the events leading to optimal drug action in the joint space over a desired time period. This includes a brief account on (patho)physiological conditions and novel potential drug targets (and their location within the synovial space). Particular emphasis is paid to (i) the potential feasibility of various depot formulation principles for the intra-articular route of administration including their manufacture, drug release characteristics and in vivo fate, and (ii) how release, mass transfer and equilibrium processes may affect the intra-articular residence time and concentration of the active species at the ultimate receptor site.

Pharmacokinetic study of methotrexate following intra-articular injection of methotrexate loaded poly(L-lactic acid) microspheres in rabbits

The pharmacokinetics and tissue distribution of methotrexate (MTX) were investigated following intra-articular injection of either MTX solution or controlled release MTX loaded microspheres in healthy rabbit joints. MTX solution or MTX loaded microspheres (size 30-100 mum) (10 mg MTX) was injected into the right knee joint cavity of rabbits. Blood samples were taken at predetermined times from the jugular vein. Urine samples were also collected over time periods up to 24 h. The major organs and synovial tissues were removed for analysis 6 and 24 h post-injection (n = 4). MTX and 7-OH-MTX concentrations in the plasma and major organs were determined by HPLC. The MTX plasma area under the concentration-time curve (AUC) for rabbits injected with MTX solution was seven fold higher than that of the rabbits injected with MTX microspheres, while t(1/2) and mean residence time (MRT) were not significantly different between two treatment groups. Four fold more MTX was excreted in the urine from rabbits injected with MTX solution compared to those injected with MTX loaded microspheres 24 h following intra-articular injection. The concentration of MTX in the synovial tissues following intra-articular injection was significantly higher in the rabbits injected with microspheres than in the rabbits injected with MTX solution. MTX solution was rapidly cleared from the joint cavity while MTX encapsulated microspheres retained MTX in the joint cavity.

Human urinary trypsin inhibitor inhibits the activation of pro-matrix metalloproteinases and proteoglycans release in rabbit articular cartilage

Treatment of primary cultured chondrocytes from rabbit articular cartilage with interleukin-1 (IL-1)alpha and plasminogen induced the production of pro-matrix metalloproteinase 1 (proMMP-1/interstitial collagenase), proMMP-3 (stromelysin 1) and proMMP-9 (gelatinase B), as well as their active forms. Human urinary trypsin inhibitor (UTI), a multipotent inhibitor of serine proteases, including plasmin inhibited the activation of proMMP-1, proMMP-3 and proMMP-9 when added to the culture medium together with IL-1alpha and plasminogen, in a dose-dependent manner. Moreover, UTI inhibited the release of proteoglycans induced by IL-1alpha and plasminogen from rabbit articular cartilage explants. These findings strongly suggest that UTI inhibits the destruction of articular cartilage induced by plasmin and/or MMPs. Thus, UTI probably exert an anti-osteoarthritic action via inactivation of proMMPs.