Permeability of olmesartan medoxomil from lipid based and suspension formulations using an optimized HDM-PAMPA model.

Hexadecane membrane-parallel artificial membrane permeability assay (HDM-PAMPA) is based on an artificial HDM that separates the two compartments (donor and acceptor compartment). This model is used to predict the permeability of drugs in gastrointestinal tract and to simulate the passive absorption. In vivo behavior of the drugs can be estimated with these systems in drug development studies. In our study, we optimized HDM-PAMPA model to determine permeability of olmesartan medoxomil (OM) lipid based drug delivery system (OM-LBDDS). In order to prove that LBDDS formulation facilitates the weak permeability of OM, permeation rates were compared with the OM suspension formula (containing 0.25% v/w carboxymethylcellulose). The experiment was performed on a 96-well MultiScreen® PAMPA filter plate (MAIPN4510). The permeability of olmesartan formulations from the donor to acceptor compartment separated by a HDM membrane were determined by the previous validated HPLC method. We created positive control series without coating HDM to present the LBDDS and suspension formulation permeability from uncoated plates. The effective permeability constant (Pe) was calculated by the formula and improvement of permeability of OM-LBDDS formulation from HDM was confirmed. On the contrary there was no permeation of OM-Suspension in the hexadecane coated plates. As a result, the intestinal permeability of OM-LBDDS was calculated to be at least 100 times more than the suspension. OM-Suspension permeation was only observed in the hexadecane uncoated positive control plates. This was also manifestation of HDM-PAMPA mimicking permeability of intestines because of its lipidic construction.

Comparison of Pharmacodynamics and Celiac Effects of Olmesartan Medoxomil Formulations by using Olmesartan-induced Celiac-rat-model.

INTRODUCTION: Olmesartan Medoxomil (OM) is an angiotensin receptor blocker and has the adverse effect of celiac like enteropathy which was accepted by the FDA in 2013. This disease is characterized by severe diarrhea, weight loss and enteropathy. Although there are many case reports associated with olmesartan-related enteropathy in humans, it has not been described in a long-term animal model study so far. AIM: We developed a self-microemulsifying drug delivery system (OM-SMEDDS) in our previous study to reduce this side effect of the drug and to enhance bioavailability. METHODS: In this study, an artificial hypertension model was established with a dose of 185 µmol /kg L-NAME (N ω-nitro-L-arginine methyl ester) twice in a day intraperitoneally in Wistar albino rats. To determine and compare side effects, the OM-Suspension and OM-SMEDDS were administered at 1.3 mg/kg therapeutic dose during one-month period to the rats. RESULTS: Tension of rats was recorded by measuring from their tails with non invasive blood pressure system. We observed celiac like enteropathy findings like villous atrophy and intraepithelial lymphocytosis and clinical changes like weight loss and severe diarrhea after the treatment with OM-Suspension during one-month experiment. It was also observed that the antihypertensive efficacy of the OM-SMEDDS formulation was higher than the suspension during the experiment, which did not cause enteropathy, diarrhea and weight loss by reducing intestinal exposure. CONCLUSION: Hereby, we evaluated the side effects of two different pharmaceutical forms by designing a sustainable and reproducible celiac rat model that can be induced with olmesartan medoxomil.

Visualisation of real-time oral biodistribution of fluorescent labeled self-microemulsifying drug delivery system of olmesartan medoxomil using optical imaging method.

In the present study, the biodistribution of self-microemulsifying drug delivery system of hydrophobic olmesartan medoxomil (OM-SMEDDS) was determined by labeling with a fluorescent dye VivoTag®680 XL and Xenolight® DiR. Labeled OM-SMEDDS and control dye solution administered orally to mice; real-time dynamic biodistributions over 7 h were determined by 2D-fluorescent imaging to verify their anatomic location. Fluorescent Emissions by Vivotag 680® XL and Xenolight® DiR labeled OM-SMEDDS emitted 2 to 24 times stronger emission than control dye administered group. To further confirm the results, organs were removed and examined using the same technique at the end of 7 h. VivoTag®680XL and Xenolight® DiR emitted 4 and 1.7 times stronger emission respectively than control dye administered mice in ex-vivo organ imaging studies. This study showed that OM-SMEDDS can be succesfully labeled with fluorescent dye and tracked with optical imaging method for the visualisation of biodistribution of drugs and is also useful for enhanced bioavailability.

Design and development of a self-microemulsifying drug delivery system of olmesartan medoxomil for enhanced bioavailability.

Olmesartan medoxomil (OM) is a hydrophobic antihypertensive drug with low bioavailability (26%) and is known to have adverse effects such as celiac disease and enteropathy. The purpose of this study was to develop SMEDDS to increase bioavailability and decrease potential side effects of OM. Hydrophilic lipophilic balance was calculated by testing solubility of OM in different oils, surfactants, and cosurfactants to obtain the most suitable combination of SMEDDS. Pseudoternary phase diagram was used to select the better oil/water formulation of SMEDDS. After a test for 3-month stability, dissolution tests and parallel artificial membrane permeability assay (PAMPA) were conducted to investigate drug solubility and permeability. Biodistribution of fluorescent marked SMEDDS was observed by using in vivo imaging system. The pharmacodynamics of the drug were determined by measuring blood pressure from tails of rats. At the end of the experiment, intestines were examined for adverse effects of OM. Compared with tablet formulation according to the dissolution study, SMEDDS formulation showed 1.67 times improvement in solubility of OM. PAMPA studies suggested a much faster permeability rate for OM SMEDDS compared to the suspension form. Labeled SMEDDS gave 3.96 times stronger fluorescent emission than control dye administered mice in in vivo imaging system (IVIS®) studies, indicating an increased bioavailability. Treating effect of SMEDDS was 3.1 times more efficient compared to suspension in hypertensive rats. It caused neither celiac-like enteropathy nor diarrhea, during 21-day noninvasive blood pressure system (NIBP) assay. Our results suggest that SMEEDS formulation improves dissolution and oral bioavailability of OM while reducing its adverse effects.