Olmesartan medoxomil

Olmesartan medoxomil, the medoxomil ester of olmesartan, is novel and oral antagonist of angiotensin II TYPE-1 receptor (AT₁ receptor) with an inhibition constant IC₅₀ of 33 nmol/L. Through oral administration, olmesartan medoxomil is rapidly absorbed by the gastrointestinal tract converting to its active metabolite olmesartan, whose inhibition constant IC₅₀ towards AT₁ receptor is 8 nmol/L. The esterification of olmesartan with medoxomil moiety is just to improve its water solubility (from 4.5% to 28.6%). Olmesartan medoxomil is used for the treatment of hypertension, in which olmesartan dose-dependently reduces the blood pressure through arterial vasodilation and reducing sodium retention.

Reference

HR Brunner. The new oral angiotensin II antagonist olmesartan medoxomil: a concise overview. Journal of Human Hypertension (2002) 16 (Suppl 2), S13-S16

Shailesh T. Prajapati, Hitesh H. Bulchandani, Dashrath M. Patel, Suresh K. Dumaniya and Chhaganbhai N. Patel. Formulation and evaluation of liquisolid compacts for olmesartan medoxomil. Journal of Drug Delivery 2013.

Development of olmesartan medoxomil optimized nanosuspension using the Box-Behnken design to improve oral bioavailability.[Pubmed:28271908]

Drug Dev Ind Pharm. 2017 Jul;43(7):1186-1196.

The aim of the present investigation was to enhance the oral bioavailability of Olmesartan medoxomil by improving its solubility and dissolution rate by preparing nanosuspension (OM-NS), using the Box-Behnken design. In this, four factors were evaluated at three levels. Independent variables include: concentration of drug (X1), concentration of surfactant (X2), concentration of polymer (X3) and number of homogenization cycles (X4). Based on preliminary studies, the size (Y1), zeta potential (ZP) (Y2) and % drug release at 5 min (Y3) were chosen as dependent responses. OM-NS was prepared by high pressure homogenization method. The size, PDI, ZP, assay, in vitro release and morphology of OM-NS were characterized. Further, the pharmacokinetic (PK) behavior of OM-NS was evaluated in male wistar rats. Statistically optimized OM-NS formulation exhibited mean particle size of 492 nm, ZP of -27.9 mV and 99.29% release in 5 min. OM-NS showed more than four times increase in its solubility than pure OM. DSC and XRD analyses indicated that the drug incorporated into OM-NS was in amorphous form. The morphology of OM-NS was found to be nearly spherical with high dispersity by scanning electron microscopic studies. The PK results showed that OM lyophilized nanosuspension (NS) exhibited improved PK properties compared to coarse powder suspension and marketed tablet powder suspension (TS). Oral bioavailability of lyophilized NS was increased by 2.45 and 2.25 folds when compared to marketed TS and coarse powder suspension, respectively. Results of this study lead to conclusion that NS approach was effective in preparing OM formulations with enhanced dissolution and improved oral bioavailability.

Development of olmesartan medoxomil lipid-based nanoparticles and nanosuspension: preparation, characterization and comparative pharmacokinetic evaluation.[Pubmed:28290712]

Artif Cells Nanomed Biotechnol. 2018 Feb;46(1):126-137.

The aim was to enhance the oral bioavailability of Olmesartan medoxomil (OM) by preparing solid lipid nanoparticles (SLNs) and comparing with nanosuspension (OM-NS). OM-SLNs and OM-NS were prepared by known methods. Prepared SLNs were evaluated for physical characters and in vivo pharmacokinetic (PK) performance in rats. OM-NS showed more than four-fold increase in the solubility. During DSC and XRD studies, drug incorporated in SLNs was found to be in amorphous form. The relative bioavailability of OM-SLN and OM-NS was 7.21- and 3.52-fold when compared with that of coarse suspension. Further, OM-SLNs also increased the oral bioavailability by two-fold over that of OM-NS.

Formulation, optimization, and in vitro-in vivo evaluation of olmesartan medoxomil nanocrystals.[Pubmed:28116656]

Drug Deliv Transl Res. 2017 Apr;7(2):292-303.

The aim of the present study is to increase the saturation solubility and oral bioavailability of Olmesartan medoxomil (OLM) using nano-sized crystals produced using a combination of antisolvent precipitation and high-shear homogenization. A response surface design comprising 46 runs was used to optimize the OLM nanocrystal formulation. The optimized formulation was produced using a combination of D-alpha tocopheryl polyethylene glycol 1000 succinate (TPGS) (0.7% w/v), Pluronic F-68(R) (0.5% w/v), and drug concentration (0.2% w/v) and subjected to 10 and 15 homogenization cycles at 1000 and 1700 bar, respectively. The particle size, polydispersity index (PDI), and zeta potential of optimized formulation were found to be 140 +/- 10.34 nm, 0.07 +/- 0.016, and -21.43 +/- 2.33 mV, respectively. The optimized formulation exhibited irregular morphology as evaluated by scanning electron microscopy and was crystalline as determined by thermal analysis and powder X-ray diffraction studies. OLM nanocrystals showed a marked increase in the saturation solubility as well as rapid dissolution rate in comparison with the pure drug. No significant change in the particle size, PDI, and zeta potential was observed when optimized formulation was stored at room and refrigeration conditions for 3 months. Lastly, in vivo pharmacokinetic studies in Sprague-Dawley rats substantiate the ability of OLM nanocrystal formulation to significantly improve ( approximately 4.6-fold) the oral bioavailability of OLM in comparison with the free drug. This study has established a potential and commercial viable OLM formulation with enhanced saturation solubility and in vivo oral bioavailability.

Nanostructured lipid carriers of olmesartan medoxomil with enhanced oral bioavailability.[Pubmed:28284054]

Colloids Surf B Biointerfaces. 2017 Jun 1;154:10-20.

The current study explores the potential of nanostructured lipid carriers (NLCs) for oral bioavailability enhancement of Olmesartan medoxomil (OLM) by systemic design approach. OLM-NLC was successfully prepared with optimized process parameters (i.e. amount of liquid lipid, total amount of lipid, drug content and surfactant concentration) using the Box-Behnken design of experiments for different response parameters (i.e. particle size, Polydispersity index and entrapment efficiency). Further, optimized formulation was validated which depicted nano size, homogenous distribution with optimum entrapment efficiency. OLM-NLC was characterized by different techniques viz. differential scanning calorimetry (DSC), powder X-Ray diffraction (PXRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM), which showed reduced crystallinity of the drug with smooth spherical appearance of nanoparticles. Formulation was found to be stable in simulated gastric fluids as no significant changes were found in size, PDI and entrapment efficiency. In vitro release showed extended release of OLM from OLM-NLC. In vitro cellular uptake study revealed 5.2 folds higher uptake of nanoparticles as compare to the free drug, when incubated with Caco-2 cells. In vivo performance showed that AUCtotal and Cmax of OLM-NLC were found significantly (P<0.01) higher as compare to the free drug. Overall, the present study successfully reports the improvement of oral bioavailability of Olmesartan medoxomil.

Effects of angiotensin AT1 receptor antagonist on volume overload-induced cardiac gene expression in rats.[Pubmed:9220278]

Hypertens Res. 1997 Jun;20(2):133-42.

The present study was undertaken to examine the effects of volume overload on cardiac gene expression and the possible role of angiotensin AT1 receptor in such expression. Cardiac volume overload was prepared by abdominal aortocaval shunt in rats. Rats with aortocaval shunt were treated with 1) vehicle, 2) an angiotensin AT1 receptor antagonist, CS-866 (10 mg/kg/d), or 3) an angiotensin-converting enzyme inhibitor, temocapril (10 mg/kg/d), for 7 days. Cardiac tissue mRNA was measured by Northern blot analysis with specific probes. Aortocaval shunt not only caused cardiac hypertrophy but also upregulated the gene expression of atrial natriuretic polypeptide, collagen III, and downregulated Ca(2+)-ATPase expression in the left ventricle. These changes were prevented by treatment with CS-866, while temocapril failed to normalize left ventricular Ca(2+)-ATPase expression. Unlike the left ventricle, the significant downregulation of alpha-myosin heavy chain and transforming growth factor-beta 3 by aortocaval shunt was observed in the right ventricle, and CS-866 normalized this decreased expression of transforming growth factor-beta 3. The left and right atria showed increased expression of collagen type I as well as of collagen type III and atrial natriuretic polypeptide, and these increases were more effectively prevented by CS-866 than by temocapril. Thus, the effects of cardiac volume overload on cardiac performance-related gene expression differ between the ventricles and atria. Our results suggest that AT1 receptor partially contributed to volume overload-induced changes in cardiac gene expression and that AT1 receptor antagonists and angiotensin-converting enzyme inhibitors have different effects in this model of cardiac hypertrophy.

Pharmacology of CS-866, a novel nonpeptide angiotensin II receptor antagonist.[Pubmed:8566137]

Eur J Pharmacol. 1995 Oct 16;285(2):181-8.

CS-866, (5-methyl-2-oxo-1,3-dioxolen-4-yl)methoxy-4-(1-hydroxy-1- methylethyl)-2-propyl-1-(4-[2-(tetrazol-5-yl)-phenyl]phenyl)met hylimidazol- 5-carboxylate, a prodrug type angiotensin receptor antagonist, is deesterified to the active acid, RNH-6270. RNH-6270 inhibited [125I]angiotensin II binding to bovine adrenal cortical membranes (angiotensin AT1 receptors) with an IC50 value of 7.7 nM, but not [125I]angiotensin II binding to bovine cerebellar membranes (angiotensin AT2 receptors), indicating the selectivity of the compound for angiotensin AT1 receptors. In guinea pig aortas, RNH-6270 reduced the maximal response of the concentration-contractile curve for angiotensin II (pD'2 = 9.9), but had no effect on the contractile response induced by phenylephrine or KCl. In conscious rats, intravenously injected RNH-6270 inhibited angiotensin II-induced pressor responses in a dose-dependent manner, and orally administered CS-866 produced a long-lasting inhibition of angiotensin II pressor responses. SK&F-525A, a P-450 inhibitor, suppressed the angiotensin II inhibitory effect of losartan, but not that of CS-866. These results demonstrate that RNH-6270 is a potent and AT1-selective angiotensin receptor antagonist and that, after oral administration, CS-866 has a long-lasting angiotensin II inhibitory action which is not affected by drug metabolizing enzymes in the liver.