Acute gastrointestinal toxic effects of suspensions of unencapsulated and encapsulated ibuprofen in rats

The novel phospho-non-steroidal anti-inflammatory drugs, OXT-328, MDC-22 and MDC-917, inhibit adjuvant-induced arthritis in rats

BACKGROUND AND PURPOSE

The use of non-steroidal anti-inflammatory drugs (NSAIDs) in the treatment of rheumatoid arthritis (RA) is limited by their toxicity. We evaluated the anti-inflammatory efficacy and safety of three novel modified NSAIDs, phospho-aspirin, phospho-ibuprofen and phospho-sulindac.

EXPERIMENTAL APPROACH

We determined the anti-inflammatory effects and gastrointestinal safety of the phospho-NSAIDs in the rat adjuvant arthritis model and studied their mechanism of action in cultured cells, Cytokines were measured with elisa and activation of nuclear factor-κB (NF-κB) by immunohistochemistry.

KEY RESULTS

All three phospho-NSAIDs showed less gastrointestinal toxicity than their parent compounds and demonstrated strong anti-inflammatory effects, essentially reversing joint inflammation and oedema. They have a broad but not uniform effect on the expression of relevant cytokines, in general decreasing IL-6 and IL-1β and increasing IL-10 levels in rat plasma and cultured cells. Phospho-sulindac and phospho-ibuprofen but not phospho-aspirin suppressed PGE(2) production in vitro, whereas phospho-aspirin (in contrast to aspirin) showed the same effect in vivo. In joint tissues, phospho-aspirin inhibited NF-κB activation, and suppressed inflammation and bone resorption. Phospho-aspirin also inhibited Jurkat T cell proliferation. In general, phospho-aspirin had greater efficacy but different effects upon inflammatory mediators compared with aspirin. The chemical modification of the parent NSAIDs seems crucial for their safety and efficacy.

CONCLUSIONS AND IMPLICATIONS

Phospho-aspirin, phospho-ibuprofen and phospho-sulindac were safer than their parent NSAIDs, were highly effective in rat adjuvant arthritis and inhibited many key mediators in the pathophysiology of RA. These novel compounds are promising candidate drugs for the treatment of RA and merit further evaluation.

Evidence that ibuprofen antagonizes selective actions of estrogen and tamoxifen on rat bone

Studies were performed to determine if the nonsteroidal anti-inflammatory drug ibuprofen alters bone and mineral metabolism in female rats. In experiment 1, four groups of growing rats underwent either sham operation or ovariectomy (OVX). One week later, controlled-release pellets with ibuprofen or placebo were implanted subcutaneously at the back of the neck. Following 3 weeks of treatment, rats were sacrificed and blood and bone samples were removed for serum assays and histomorphometric analysis. Body growth rate and the static cortical bone measurements made at the tibial diaphysis did not change in response to OVX. OVX, however, did increase radial bone growth, lowered serum 17beta-estradiol, reduced uterine weight, and decreased the cancellous bone area of the tibial metaphysis in the rats. Ibuprofen did not alter serum 17beta-estradiol or uterine weight but reduced radial bone growth as well as cancellous bone area of the tibial metaphysis in both sham-operated and OVX animals. In experiments 2 and 3, we tested the influence of ibuprofen on the effects of the tissue-selective estrogen agonist tamoxifen and of exogenous 17beta-estradiol in the OVX rat. Ibuprofen completely blocked the effects of tamoxifen and partially blocked the effects of 17beta-estradiol to prevent cancellous osteopenia. In contrast, ibuprofen did not influence the effects of tamoxifen and 17beta-estradiol to reduce radial bone growth. Besides the skeletal effects, ibuprofen suppressed estrogen-induced uterine growth. Our data suggest that ibuprofen blocks selective estrogen receptor-mediated activities in the rat.

Stereoselective disposition of suspensions of conventional and wax-matrix sustained release ibuprofen microspheres in rats

PURPOSE

The aim of the study is to evaluate stereoselective in vivo disposition of suspensions of conventional and wax-matrix sustained release ibuprofen microspheres in rats.

METHODS

Male wistar rats were dosed i.v. with 20 mg/kg, or orally with conventional suspension, and three suspension formulations of sustained release microspheres (having three different particle sizes) of racemic ibuprofen. Blood samples were analyzed stereoselectively by reverse phase HPLC.

RESULTS

The mean Cmax for (S)- and (R)-ibuprofen decreased with increased particle size of the drug or microspheres in the suspension dosage forms, while the Tmax increased with increased particle size. The mean S/R ratio (AUC0-48) of the suspensions decreased with increase in particle size of the drug or microspheres and these ratios (for both conventional and sustained formulations) were higher than that of the i.v., an indication of presystemic inversion. Decrease in the ratios with increased particle size is suggestive of formulation dependent inversion. The plasma concentration-time data of the sustained release formulations showed bimodal profiles, irrespective of the particle size of the microspheres. The second peak observed after 8 hours is indicative of colonic absorption.

CONCLUSIONS

Stereoselective disposition of ibuprofen microspheres showed higher bioavailability compared to the conventional suspension. Bimodal disposition is influenced by dosage form while presystemic inversion is both site-specific, and dosage form dependent.

Gastrointestinal uptake of biodegradable microparticles: effect of particle size

PURPOSE

To investigate the effect of microparticle size on gastrointestinal tissue uptake.

METHODS

Biodegradable microparticles of various sizes using polylactic polyglycolic acid (50:50) co-polymer (100 nm, 500 nm, 1 micron, and 10 microns) and bovine serum albumin as a model protein were formulated by water-in-oil-in-water emulsion solvent evaporation technique. The uptake of microparticles was studied in rat in situ intestinal loop model and quantitatively analyzed for efficiency of uptake.

RESULTS

In general, the efficiency of uptake of 100 nm size particles by the intestinal tissue was 15-250 fold higher compared to larger size microparticles. The efficiency of uptake was dependent on the type of tissue, such as Peyer's patch and non patch as well as on the location of the tissue collected i.e. duodenum or ileum. Depending on the size of microparticles, the Peyer's patch tissue had 2-200 fold higher uptake of particles than the non-patch tissue collected from the same region of the intestine. Histological evaluation of the tissue sections demonstrated that 100 nm particles were diffused throughout the submucosal layers while the larger size nano/microparticles were predominantly localized in the epithelial lining of the tissue.

CONCLUSIONS

There is a microparticle size dependent exclusion phenomena in the gastrointestinal mucosal tissue with 100 nm size particles showing significantly greater tissue uptake. This has important implications in designing of nanoparticle-based oral drug delivery systems, such as an oral vaccine system.