Absorption enhancement studies of clopidogrel hydrogen sulphate in rat everted gut sacs.

OBJECTIVES: Clopidogrel, a thienopyridine antiplatelet agent, is a poor aqueous soluble compound and a P-glycoprotein (P-gp) efflux pump substrate. These two factors are responsible for its incomplete intestinal absorption. In this study, we have attempted to enhance the absorption of clopidogrel by improving its solubility and by inhibiting intestinal P-gp activity. METHODS: Solubility enhancement was achieved by preparing solid dispersions. Quinidine and naringin were selected as P-gp inhibitors, whilst tartaric acid was selected as the intestinal absorption enhancer. Absorption studies were performed using the everted gut sac model prepared from rat jejunum. The determination of clopidogrel was performed by high performance liquid chromatography. KEY FINDINGS: We noticed an enhancement of clopidogrel absorption by improving its solubility or by inhibiting the P-gp activity. The greatest results were obtained for solid dispersions in the presence of P-gp inhibitors at their highest concentrations, with an absorption improvement of 3.41- and 3.91-fold for naringin (15mg/kg) and quinidine (200µm), respectively. However, no clopidogrel absorption enhancement occurred in the presence of tartaric acid. CONCLUSIONS: Naringin, a natural compound which has no undesirable side effects as compared with quinidine, could be used as a pharmaceutical excipient in the presence of clopidogrel solid dispersions to increase clopidogrel intestinal absorption and therefore its oral bioavailability.

The effect of etidronate on the periodontium of ovariectomized rats.

BACKGROUND: Bisphosphonates are indicated for the treatment of osteoporosis. However, they could have an adverse effect on specific sites, such as the bisphosphonate-related osteonecrosis of the jaw. The aim of this study is to investigate the effect of etidronate on the resorption and apposition sides of the periodontium in ovariectomized rats. METHODS: Twenty-four female Wistar rats were randomly subjected to either ovariectomy or sham operation. After 8 weeks, six animals of each group were sacrificed. The other 12 rats received 5 mg/kg/day etidronate subcutaneously during 4 weeks. Tartrate-resistant acid phosphatase reaction and immunohistochemical staining for receptor activator of nuclear factor-κB (RANK), RANK-ligand (RANKL), osteoprotegerin (OPG), and osteocalcin was performed. Immunoreactivity was evaluated using a semiquantitative analysis. RESULTS: In ovariectomized rats, osteoclasts were noticed in the root socket of molars, including the apposition side of the periodontium, in which RANKL expression was significantly evidenced. In the etidronate-treated group, OPG expression was significantly expressed and osteoclasts that were noticed in the resorption side remained undetected in the apposition side even under ovariectomy. RANK was significantly expressed in ovariectomized rats treated with etidronate. Osteoid formation and osteocalcin expression were described on the alveolar bone surfaces in etidronate-treated rats, with or without ovariectomy. CONCLUSIONS: Etidronate has specific site and bone cell actions in the periodontium. It inhibits the osteoclast differentiation induced by ovariectomy in the apposition side of the periodontium but maintains bone formation over all the socket surfaces. Such specificity may be related to the pathogenesis of the bisphosphonate-induced osteonecrosis of the jaw.

Comparative study of two in vitro methods for assessing drug absorption: Sartorius SM 16750 apparatus versus Everted Gut Sac.

PURPOSE: Oral drug administration remains the most common and most convenient way used in clinical therapy. The availability of a simple, rapid, economic and reproducible in vitro method to assess the rate, extent and mechanism of intestinal drug absorption is a very helpful tool. The purpose of this study was to compare the performance of Sartorius SM 16750 Absorption Simulator apparatus to Everted Gut Sac (EGS) technique in terms of predicting drug permeability. METHODS: Permeation studies across these two in vitro models were performed with six drugs selected across the Biopharmaceutics Classification System (BCS) categories: tramadol (class I of BCS), doxycycline (class I of BCS), diclofenac (class II of BCS), clopidogrel (class II of BCS), metformin (class III of BCS) and chlorothiazide (class IV of BCS). RESULTS: Apparent permeability coefficient (Papp) and diffusion profiles obtained with EGS and Sartorius SM 16750 apparatus were similar for diclofenac and metformin, whereas, we noticed significant differences (p ≤ 0.05), for tramadol, doxycycline, clopidogrel and chlorothiazide. CONCLUSION: Compared to Everted Gut Sac model, Sartorius SM 16750 absorption simulator apparatus seems to have limited application for the assessment of intestinal drug absorption since it does not take into consideration the involvement of others processes than the passive transcellular pathway as mechanism of drug absorption.

Effect of in vitro exposure to Vibrio vulnificus on hydroelectrolytic transport and structural changes of sea bream (Sparus aurata L.) intestine.

The everted gut sac technique has been used to investigate the effect of Vibrio vulnificus on water and electrolyte (Na(+), K(+), Cl(-), HCO(3)(-)) transport on the intestine of sea bream (Sparus aurata L.). Both the anterior and the posterior intestine were incubated in a medium containing 10(8) V. vulnificus cells ml(-1) at 25 degrees C for 2 h. The presence of V. vulnificus resulted in a significant reduction (P < 0.05) of water absorption in the anterior intestine, while sodium absorption in the anterior (P < 0.01) and posterior (P < 0.05) intestine was elevated. Chloride absorption was increased, but the changed was not significant, while potassium absorption decreased significantly (P < 0.05), but only in the posterior intestine. Incubation the sea bream intestine with V. vulnificus did not affect carbonate secretion in the anterior segment, whereas high secretion was stimulated in the posterior segment (P < 0.01). Histological evaluations demonstrated damage in the anterior intestine of sea bream that was characterized by the detachment of degenerative enterocytes, alterations in the microvilli, and the presence of a heterogenous cell population, indicating inflammation. Based on our results, we conclude that V. vulnificus caused cell damage to the intestine of sea bream and that the anterior intestine is more susceptible than the posterior part of the intestine. Several hypotheses are suggested to explain our observations, such as the presence of higher numbers of villosities in the anterior intestine than in the posterior one and/or the presence of endogenous bacteria in the posterior intestine which may have a protector role.