Strontium and simvastatin dual loaded hydroxyapatite microsphere reinforced poly(ε-caprolactone) scaffolds promote vascularized bone regeneration.

The promotion of vascular network formation in the early stages of implantation is considered a prerequisite for successful functional bone regeneration. In this study, we successfully constructed 3D printed scaffolds with strong mechanical strength and a controllable pore structure that can sustainably release strontium (Sr) ions and simvastatin (SIM) for up to 28 days by incorporation of Sr2+ and SIM-loaded hydroxyapatite microspheres (MHA) into a poly(ε-caprolactone) (PCL) matrix. In vitro cell experiments showed that Sr-doped scaffolds were beneficial to the proliferation and osteogenic differentiation of bone mesenchymal stem cells (BMSCs), an appropriate dose of SIM was beneficial to cell proliferation and angiogenesis, and a high dose of SIM was cytotoxic. The Sr- and SIM-dual-loaded scaffolds with an appropriate dose significantly induced osteogenic differentiation of BMSCs and tube formation of human umbilical vein endothelial cells (HUVECs) in vitro and promoted vascular network and functional bone formation in vivo. Ribose nucleic acid (RNA) sequencing analysis suggested that the mechanism of promotion of vascularized bone regeneration by fabricated scaffolds is that dual-loaded Sr2+ and SIM can upregulate osteogenic and vasculogenic-related genes and downregulate osteoclast-related genes, which is beneficial for vascular and new bone regeneration. The 3D printed composite scaffolds loaded with high-stability and low-cost inorganic Sr2+ ions and SIM small-molecule drugs hold great promise in the field of promoting vascularized bone regeneration.

Structure and Fate of Nanoparticles Designed for the Nasal Delivery of Poorly Soluble Drugs.

Nanoparticles are promising mediators to enable nasal systemic and brain delivery of active compounds. However, the possibility of reaching therapeutically relevant levels of exogenous molecules in the body is strongly reliant on the ability of the nanoparticles to overcome biological barriers. In this work, three paradigmatic nanoformulations vehiculating the poorly soluble model drug simvastatin were addressed: (i) hybrid lecithin/chitosan nanoparticles (LCNs), (ii) polymeric poly-ε-caprolactone nanocapsules stabilized with the nonionic surfactant polysorbate 80 (PCL_P80), and (iii) polymeric poly-ε-caprolactone nanocapsules stabilized with a polysaccharide-based surfactant, i.e., sodium caproyl hyaluronate (PCL_SCH). The three nanosystems were investigated for their physicochemical and structural properties and for their impact on the biopharmaceutical aspects critical for nasal and nose-to-brain delivery: biocompatibility, drug release, mucoadhesion, and permeation across the nasal mucosa. All three nanoformulations were highly reproducible, with small particle size (∼200 nm), narrow size distribution (polydispersity index (PI) < 0.2), and high drug encapsulation efficiency (>97%). Nanoparticle composition, surface charge, and internal structure (multilayered, core-shell or raspberry-like, as assessed by small-angle neutron scattering, SANS) were demonstrated to have an impact on both the drug-release profile and, strikingly, its behavior at the biological interface. The interaction with the mucus layer and the kinetics and extent of transport of the drug across the excised animal nasal epithelium were modulated by nanoparticle structure and surface. In fact, all of the produced nanoparticles improved simvastatin transport across the epithelial barrier of the nasal cavity as compared to a traditional formulation. Interestingly, however, the permeation enhancement was achieved via two distinct pathways: (a) enhanced mucoadhesion for hybrid LCN accompanied by fast mucosal permeation of the model drug, or (b) mucopenetration and an improved uptake and potential transport of whole PCL_P80 and PCL_SCH nanocapsules with delayed boost of permeation across the nasal mucosa. The correlation between nanoparticle structure and its biopharmaceutical properties appears to be a pivotal point for the development of novel platforms suitable for systemic and brain delivery of pharmaceutical compounds via intranasal administration.

Calcium Supplement by Tetracycline guided amorphous Calcium Carbonate potentiates Osteoblast promotion for Synergetic Osteoporosis Therapy.

Background: The calcium supplement is a clinically approved approach for osteoporosis therapy but usually requires a large dosage without targetability and with poor outcome. This modality is not fully explored in current osteoporosis therapy due to the lack of proper calcium supplement carrier. Methods: In this study, we constructed a tetracycline (Tc) modified and simvastatin (Sim) loaded phospholipid-amorphous calcium carbonate (ACC) hybrid nanoparticle (Tc/ACC/Sim). Results: The resulted Tc/ACC/Sim was able to enhance its accumulation at the osteoporosis site. Most importantly, the combination of calcium supplement and Sim offered synergetic osteoblast promotion therapy of osteoporosis with advanced performance than non-targeted system or mono therapy. Conclusion: This platform provides an alternative approach to stimulate bone formation by synergetic promotion of osteoblast differentiation using calcium supplement and Sim.

Co-Amorphous Simvastatin-Nifedipine with Enhanced Solubility for Possible Use in Combination Therapy of Hypertension and Hypercholesterolemia.

The high index of simultaneous incidence of hypertension and hypercholesterolemia in the population of many countries demands the preparation of more efficient drugs. Therefore, there is a significant area of opportunity to provide as many alternatives as possible to treat these illnesses. Taking advantage of the solubility enhancement that can be achieved when an active pharmaceutical ingredient (API) is obtained and stabilized in its amorphous state, in the present work, new drug-drug co-amorphous formulations (Simvastatin SIM- Nifedipine NIF) with enhanced solubility and stability were prepared and characterized. Results show that the co-amorphous system (molar ratio 1:1) is more soluble than the pure commercial APIs studied separately. Aqueous dissolution profiles showed increments of solubility of 3.7 and 1.7 times for SIM and NIF, correspondingly, in the co-amorphous system. The new co-amorphous formulations, monitored in time, (molar fractions 0.3, 0.5 and 0.7 of SIM) remained stable in the amorphous state for more than one year when stored at room temperature and did not show any signs of crystallization when re-heating. Inspection on the remainder of a sample after six hours of dissolution showed no recrystallization, confirming the stability of co-amorphous system. The enhanced solubility of the co-amorphous formulations makes them promising for simultaneously targeting of hypertension and hypercholesterolemia through combination therapy.

Development and validation of a RP-HPLC method for the simultaneous detection and quantification of simvastatin's isoforms and coenzyme Q10 in lecithin/chitosan nanoparticles.

Hybrid nanocapsules constituted of phospholipids and polysaccharides have been proposed as colloidal systems for the delivery of drugs via non-parenteral administration routes, due their capacity of high drug loading, controlled drug release and targeted delivery to the specific organ. Moreover, nanoparticles systems offer the possibility of co-encapsulation of drugs in the same drug delivery system and, consequently, the simultaneous administration of compounds. Characterization of nanoparticles properties, specifically involves quantification of the active pharmaceutical ingredients and is pivotal in the development of innovative nanomedicines. Therefore, this study has proposed and validated a new RP-HPLC-UV method for the simultaneous determination of simvastatin and coenzyme Q10 in hybrid nanoparticles systems. A reversed phase (RP) C8 column and a gradient elution of water: methanol at flow rate of 1.5 ml/min was used. Simvastatin (SVT), simvastatin hydroxyacid isoform (SVA) and coenzyme Q10 were identified by dual wavelength-UV detection at 238 nm (statins) and 275 nm, respectively. The proposed method was selective and linear in the range of 0.5-25 µg/ml (r2 > 0.999), precise, with values of relative standard deviation (RSD) lower than 2%, robust and accurate (recovery values of 100 ±â€¯5%), satisfying FDA guidelines. Furthermore, low detection (LOD <0.2 µg/ml) and quantification limits (LOQ <0.4 µg/ml) were suitable for the application of the method for the in vitro study of release kinetics of simvastatin and coenzyme Q10 co-encapsulated in lecithin/chitosan nanoparticles. The proposed method represents, to our knowledge, the only method for the simultaneous quantification of simvastatin, coenzyme Q10 and of the hydrolysed hydroxyacid isoform of the statin in nanoparticles.

Nanostructured lipid carriers for improved oral delivery and prolonged antihyperlipidemic effect of simvastatin.

The purpose of the current study is to develop nanostructured lipid carriers (NLCs) for the delivery of the antihyperlipidemic drug simvastatin (SIM) to increase its extremely low oral bioavailability (<5%) and prolong its antihyperlipidemic effect. NLCs were prepared via emulsification-solvent evaporation technique followed by ultrasonication, and the effect of composition of the nanocarriers on the particle size, size distribution, surface charge, entrapment efficiency, drug release kinetics and physical stability was extensively studied. NLCs exhibited nanosized (<200nm) spherical morphologies with narrow size distribution and high drug entrapment efficiency (>75%), sustained drug release pattern, and negative surface charge (zeta potential of -35-40mV) that imparts sufficient electrostatic physical stability. When tested in vivo, SIM-NLCs of the optimal composition demonstrated improved and prolonged reduction in the total cholesterol and non-high density lipoprotein cholesterol levels, as compared to the drug suspension. After oral administration of a single dose of SIM-NLC, 4-fold increase in bioavailability was observed, as compared to the SIM suspension. Hence, NLCs might provide efficient nanodevices for the management of hyperlipidemia and promising drug delivery systems to enhance SIM oral bioavailability.

Optimization, characterization, and in vitro assessment of alginate-pectin ionic cross-linked hydrogel film for wound dressing applications.

Natural polymer-based hydrogel films have great potential for biomedical applications and are good candidates for wound dressings. In this study, we aimed to develop simvastatin-loaded crosslinked alginate-pectin hydrogel films by ionic crosslinking to improve the mechanical characteristics, wound fluid uptake and drug release behavior. Alginate-pectin hydrocolloid films were chemically crosslinked by immersing in different concentrations of CaCl2 (0.5-3% w/v) for 2-20min. The degree of crosslinking was influenced by both contact time and CaCl2 concentration. The optimized conditions for crosslinking were 0.5% and 1% (CaCl2) for 2min. The optimized hydrogel films were then characterized for their physical, mechanical, morphological, thermal, in vitro drug release, and cytocompatibility profiles. Crosslinking improved the mechanical profile and wound fluid uptake capacity of dressings. The hydrogel films were able to maintain their physical integrity during use, and the best results were obtained with the film in which the extent of crosslinking was low (0.5%). Thermal analysis confirmed that the crosslinking process enhanced the thermal stability of hydrogel films. Sustained, slow release of simvastatin was obtained from the crosslinked films and in vitro cytotoxicity assay demonstrated that the hydrogel films were non-toxic.

Supramolecular inclusion complexation of simvastatin with methylated ß-cyclodextrins for promoting osteogenic differentiation.

Statins are recognized as a potential candidate to induce the regeneration of bone. However, statins are a strongly hydrophobic drug and it is difficult to administer at the local sites. In this study, the inclusion complexes of simvastatin (SV) with hydroxypropyl-ß-cyclodextrin (HP-ß-CD) and randomly methylated ß-cyclodextrin (RM-ß-CD) were prepared to improve the water-solubility and the osteogenic differentiation ability of the inclusion complexes in MC3T3-E1 cells was investigated. The water-solubility of SV increased linearly upon the addition of both HP-ß-CD and RM-ß-CD, due to the formation of inclusion complexes. The osteogenic differentiation ability of the inclusion complexes were evaluated by the production of alkaline phosphatase (ALP) and late stage osteogenetic gene expression in MC3T3-E1 cells after 14 days of culture. As a result, the RM-ß-CD/SV inclusion complexes showed significantly higher ALP production and the expression of bone sialoprotein (BSP) and osteocalcin (OCN) than the untreated and free SV-treated cells. Additionally, the production of bone morphogenetic protein-2 (BMP-2) from MC3T3-E1 cells after the treatment with RM-ß-CD/SV inclusion complexes was significantly higher than the untreated and free SV-treated cells. Accordingly, it is concluded that the inclusion complexation of SV with RM-ß-CD is a potential formulation for bone regenerative therapy to improve water-solubility and osteodifferentiation efficiency.

Bioavailability assessment of hydroxymethylglutaryl coenzyme A reductase inhibitor utilizing pulsatile drug delivery system: a pilot study.

Chronotherapy or pulsatile drug delivery system could be achieved by increasing drug plasma concentration exactly at the time of disease incidence. Cholesterol synthesis shows a circadian rhythm being high at late night and early in the morning. Simvastatin (SIM) inhibits hydroxymethylglutaryl coenzyme A reductase, which is responsible for cholesterol synthesis. In this study, SIM lipid-based formulation filled in gelatin capsules and coated with aqueous Eudragit® S100 dispersion was prepared for chronotherapeutic treatment of hypercholesterolemia. The pharmacokinetic parameters of SIM capsules were studied in human volunteers after a single oral dose and compared with that of Zocor® tablets as a reference in a randomized cross-over study. Pharmacokinetic parameters such as AUC0-∞, Cmax, Tmax, t1/2 and elimination rate constant were determined from plasma concentration-time profile for both formulations. The tested formulation had the ability to delay drug absorption and provide higher drug concentrations from 3 up to 10 h after oral administration compared to that of commercial tablets. The data in this study revealed that the prepared formulation could be effective in chronotherapeutic treatment of hypercholesterolemia. Moreover, the tested formulation was found to enhance SIM bioavailability by 29% over the reference tablets.

Development and physicochemical characterization of alginate composite film loaded with simvastatin as a potential wound dressing.

Previously, studies have demonstrated that topical application of simvastatin can promote wound healing in diabetic mice via augmentation of angiogenesis and lymphangiogenesis. This study aimed to formulate and characterize simvastatin in alginate-based composite film wound dressings. Biopolymers used for composite films were sodium alginate blended with pectin or gelatin. The films were prepared and characterized based on their physical properties, surface morphology, mechanical strength and rheology. Then, in vitro drug releases from the films were investigated and, finally, the cell viability assay was performed to assess the cytotoxicity profile. From the pre-formulation studies, alginate/pectin composite film showed to possess desirable wound dressing properties and superior mechanical properties. The in vitro drug release profile revealed that alginate/pectin film produced a controlled release drug profile, and cell viability assay showed that the film was non-toxic. In summary, alginate/pectin composite film is suitable to be formulated with simvastatin as a potential wound dressing.

Attenuation of acetylcholine activated potassium current (I KACh) by simvastatin, not pravastatin in mouse atrial cardiomyocyte: possible atrial fibrillation preventing effects of statin.

Statins, 3-hydroxy-3-methyl-glutaryl-CoA reductase inhibitors, are associated with the prevention of atrial fibrillation (AF) by pleiotropic effects. Recent clinical trial studies have demonstrated conflicting results on anti-arrhythmia between lipophilic and hydrophilic statins. However, the underlying mechanisms responsible for anti-arrhythmogenic effects of statins are largely unexplored. In this study, we evaluated the different roles of lipophilic and hydrophilic statins (simvastatin and pravastatin, respectively) in acetylcholine (100 µM)-activated K+ current (IKACh, recorded by nystatin-perforated whole cell patch clamp technique) which are important for AF initiation and maintenance in mouse atrial cardiomyocytes. Our results showed that simvastatin (1-10 µM) inhibited both peak and quasi-steady-state IKACh in a dose-dependent manner. In contrast, pravastatin (10 µM) had no effect on IKACh. Supplementation of substrates for the synthesis of cholesterol (mevalonate, geranylgeranyl pyrophosphate or farnesyl pyrophosphate) did not reverse the effect of simvastatin on IKACh, suggesting a cholesterol-independent effect on IKACh. Furthermore, supplementation of phosphatidylinositol 4,5-bisphosphate, extracellular perfusion of phospholipase C inhibitor or a protein kinase C (PKC) inhibitor had no effect on the inhibitory activity of simvastatin on IKACh. Simvastatin also inhibits adenosine activated IKACh, however, simvastatin does not inhibit IKACh after activated by intracellular loading of GTP gamma S. Importantly, shortening of the action potential duration by acetylcholine was restored by simvastatin but not by pravastatin. Together, these findings demonstrate that lipophilic statins but not hydrophilic statins attenuate IKACh in atrial cardiomyocytes via a mechanism that is independent of cholesterol synthesis or PKC pathway, but may be via the blockade of acetylcholine binding site. Our results may provide important background information for the use of statins in patients with AF.

Synthesis and characterization of cationic polymeric nanoparticles as simvastatin carriers for enhancing the osteogenesis of bone marrow mesenchymal stem cells.

Simvastatin (SIM) can increase osteoblast activity and enhance osteogenesis. However, some limitations of SIM have been noted, such as statin-associated rhabdomyolysis and its poor solubility in water. In this study, we fabricated new cationic nanoparticles (NPs) designed for the controlled release of hydrophobic SIM and endocytosis by cells with the aim of reducing the total required amount of SIM administered and enhancing the osteogenesis of bone marrow mesenchymal stem cells (BMSCs). New copolymers of bis(poly(lactic-co-glycolic acid)-phenylalanine-polyethylene glycol)-quaternary ammonium grafted diethyltriamine (bis(PLGA-phe-PEG)-qDETA; BPPD) were created using a diethyltriamine-quaternary ammonium (qDETA) moiety, hetero-bifunctional polyethylene glycol (COOH-PEG-NH2), phenylalanine (phe) and poly(lactic-co-glycolic acid) (PLGA). SIM encapsulated in BPPD NPs (SIM/BPPD) was fabricated using a water-miscible solvent. The size distributions of BPPD NPs and SIM/BPPD NPs, the encapsulation efficacy and the in vitro release profile of SIM in SIM/BPPD NPs over 6days were investigated. Based on the results of Alizarin Red S staining, alkaline phosphatase (ALP) activity assays and quantitative polymerase chain reaction (Q-PCR) results, we propose that SIM/BPPD NPs may induce osteogenesis in BMSCs by enhancing the expression of an osteogenic gene, which subsequently elevates ALP activity and mineralization, resulting in enhanced BMSC osteogenesis. These results suggest that the SIM/BPPD NPs may be used as hydrophobic drug carriers to reduce the total required amount of SIM administered and to provide an effective SIM release mechanism for enhancing BMSC osteogenesis. Surprisingly, BPPD NPs were also shown to have the ability to promote osteogenesis in BMSCs by enhancing the expression of osteogenic genes, especially osteocalcin (OC), and subsequently elevating ALP activity and mineralization.

Over the counter drugs (and dietary supplement) exercise: a team-based introduction to biochemistry for health professional students.

For successful delivery of basic science topics for health-professional students, it is critical to reduce apprehension and illustrate relevance to clinical settings and everyday life. At the beginning of the Biochemistry course for Physician Assistants, a team-based assignment was designed to develop an understanding of the mechanism of action, effectiveness, and toxicity of five common over the counter (OTC) drugs and dietary supplements, and place these familiar medicines in a political and historical context. The objectives of this exercise were to stimulate interest in biochemistry; to provide basic information on enzymes and enzyme inhibitors related to these drugs to be expanded upon later in the course; and to encourage active and interactive learning. Teams of five students were formed, and each student was given an information sheet on aspirin, alpha-galactosidase, orlistat, dextromethorphan, or simvastatin, a low dose statin, which was previously available without prescription at pharmacies in the UK. After each member of the team acquired information on one OTC drug/dietary supplement by reading an assigned information sheet, the team was asked to go through a series of questions, and then submit answers to a quiz as a group. A high rate of success on the quiz, an overwhelmingly positive response on formal course evaluations, and enthusiastic exchanges during class suggested this team-based session accomplished its goals.

Comparative effects of high and low-dose simvastatin on prostate epithelial cells: the role of LDL.

Epidemiological studies have linked statin use with a decreased risk of advanced prostate cancer and an improved recurrence-free survival after radical therapy. It is unclear, however, whether statins could have direct effects against prostate cancer in a clinical setting, as their growth-inhibiting effects on prostate cancer cells have been demonstrated at drug concentrations which exceed the level in plasma during standard clinical dosing. We compared responses to high-dose and therapeutic-dose simvastatin in normal and cancerous prostate epithelial cells. Simvastatin was more effective at inhibiting the growth of normal prostate epithelial cells than of cancer cells. At therapeutic 100 nM concentration simvastatin had a cytostatic effect on normal cells: apoptosis was only slightly induced, but a decrease in cell cycle activity and an increase in senescence were observed. At therapeutic concentrations, lipophilic simvastatin caused a stronger growth inhibition than did hydrophilic rosuvastatin. In contrast, 10 µM simvastatin had a cytotoxic effect both on normal and cancer cells. Addition of LDL-cholesterol effectively reversed the cytostatic effect in all cell lines, but overcoming the cytotoxicity of 10 µM simvastatin required a combination of LDL-cholesterol and mevalonate. As LDL-cholesterol completely prevented the growth-inhibiting effect of therapeutic-dose simvastatin already at low, subphysiological concentrations it is unlikely that statins have direct effects on growth of prostate epithelial cells in vivo. Statins' possible benefits against prostate cancer could be due to systemic cholesterol-lowering, as suggested by epidemiological studies. Future clinical studies evaluating the effects of statins on prostate cancer prevention should monitor serum LDL and should probably administer statins at higher concentrations than those currently used in the treatment of hypercholesterolemia.

Topical anti-inflammatory effect of hypocholesterolaemic drugs.

OBJECTIVES: The topical anti-inflammatory effect of simvastatin, atorvastatin, pravastatin, ezetimibe and combined ezetimibe + simvastatin was investigated, using the croton oil model of ear oedema in mice. METHODS: Simvastatin, atorvastatin, pravastatin, ezetimibe and ezetimibe + simvastatin combination (dissolved in 20 µl of 70% acetone) were topically applied simultaneously with croton oil (200 µg/ear, dissolved in 20 µl of 70% acetone) at the inner surface of each ear. Ear oedema and myeloperoxidase activity, indicative of polymorphonuclear cell migration, were assessed 6 h after inflammatory stimuli. KEY FINDINGS: It was found that statins can act as topical anti-inflammatories, but the pharmacological effect is dependent on statin polarity. At 0.3 mg/ear inhibition of ear oedema was 79%, 67% and 40% for simvastatin, atorvastatin and pravastatin, respectively. Simvastatin and atorvastatin also remarkably diminished myeloperoxidase activity, even at low concentrations (0.03 mg/ear). Pravastatin, the most polar statin, however, did not cause any reduction in ear oedema or myeloperoxidase activity at low doses. The order of topical anti-inflammatory activity was pravastatin < < < atorvastatin ≤ simvastatin. Ezetimibe, another hypocholesterolaemic drug, also presented anti-inflammatory effects, inhibiting ear oedema by 64% at 0.3 mg/ear. However, when used in combination with simvastatin, no further beneficial effect was observed. CONCLUSIONS: These results consistently support current evidence showing that statins can be used for treatment of dermatological disorders. Polarity of the molecule, however, is a factor that should be considered before recommending use.

Preparation and evaluation of nicotinic acid sustained-release pellets combined with immediate release simvastatin.

This study was performed to prepare high-dose nicotinic acid (NA) loaded sustained-release pellets coated with double polymer and simvastatin (SIM). The uncoated pellets were prepared by extrusion-spheronization and the double ethylcellucose (EC) films were coated in a bottom-spray fluidized bed coater. SIM was milled by wet grinding and then the milled suspension was layered on the coated pellets. Results showed that coated with 1.5% subcoating and 1% outer coating composed of EC and polyvinyl pyrrolidone K30 (PVP(K30)) in ratios of 5:1 and 2:1, NA release behavior was very similar to the reference (NER/S; SIMCOR, Abbott) in different media. And SIM was delivered more rapidly than that of the reference, while the SIM layer had no influence on NA release. During 6-month storage at 40°C/75% RH, the two drugs exhibited stable dissolution behavior. It was observed that the content uniformity of SIM was provided by the present preparation and SIM was stable if adding light magnesium oxide in the grinding procedure. Results indicated it was possible to prepare high-dose sustained-release NA pellets combined with little-dose immediate release SIM by spraying double EC polymer and SIM milled suspension on NA pellets in a bottom-spray fluidized bed coater, respectively.

Co-solvent evaporation method for enhancement of solubility and dissolution rate of poorly aqueous soluble drug simvastatin: in vitro-in vivo evaluation.

A number of synthesized chemical molecules suffer from low aqueous solubility problems. Enhancement of aqueous solubility, dissolution rate, and bioavailability of drug is a very challenging task in drug development. In the present study, solubility and dissolution of poorly aqueous soluble drug simvastatin (SIM) was enhanced using hydrophilic, low viscosity grade polymer hydroxypropyl methylcellulose (HPMC K(3)LV). The co-solvent evaporation method was developed for efficient encapsulation of hydrophobic drug in polymer micelles of HPMC K(3)LV. Spray drying and rotaevaporation method were applied for solvent evaporation. Co-solvent-evaporated mixture in solid state was determined by differential scanning calorimetry (DSC), X-ray diffraction studies (XRD), scanning electron microscopy, and Fourier-transform infrared spectroscopy. In vitro-in vivo studies were performed on co-solvent-evaporated mixture and compared with SIM. In vivo study was conducted on healthy albino rats (Wister strain), and formulations were administered by oral route. Results of the study show the conversion of crystalline form of SIM into amorphous form. The dissolution rate was remarkably increased in co-solvent-evaporated mixtures compared to SIM. co-solvent-evaporated mixtures showed better reduction in total cholesterol and triglyceride levels than the SIM. The low-viscosity grade HPMC acts as a surfactant, which enhances the wetting of drug and thus improves the solubility of drug. The co-solvent evaporation method provides good encapsulation efficiency and produces amorphous form of SIM, which gave better solubility and dissolution than the crystalline SIM.

Can in vitro metabolism-dependent covalent binding data in liver microsomes distinguish hepatotoxic from nonhepatotoxic drugs? An analysis of 18 drugs with consideration of intrinsic clearance and daily dose.

In vitro covalent binding assessments of drugs have been useful in providing retrospective insights into the association between drug metabolism and a resulting toxicological response. On the basis of these studies, it has been advocated that in vitro covalent binding to liver microsomal proteins in the presence and the absence of NADPH be used routinely to screen drug candidates. However, the utility of this approach in predicting toxicities of drug candidates accurately remains an unanswered question. Importantly, the years of research that have been invested in understanding metabolic bioactivation and covalent binding and its potential role in toxicity have focused only on those compounds that demonstrate toxicity. Investigations have not frequently queried whether in vitro covalent binding could be observed with drugs with good safety records. Eighteen drugs (nine hepatotoxins and nine nonhepatotoxins in humans) were assessed for in vitro covalent binding in NADPH-supplemented human liver microsomes. Of the two sets of nine drugs, seven in each set were shown to undergo some degree of covalent binding. Among hepatotoxic drugs, acetaminophen, carbamazepine, diclofenac, indomethacin, nefazodone, sudoxicam, and tienilic acid demonstrated covalent binding, while benoxaprofen and felbamate did not. Of the nonhepatotoxic drugs evaluated, buspirone, diphenhydramine, meloxicam, paroxetine, propranolol, raloxifene, and simvastatin demonstrated covalent binding, while ibuprofen and theophylline did not. A quantitative comparison of covalent binding in vitro intrinsic clearance did not separate the two groups of compounds, and in fact, paroxetine, a nonhepatotoxin, showed the greatest amount of covalent binding in microsomes. Including factors such as the fraction of total metabolism comprised by covalent binding and the total daily dose of each drug improved the discrimination between hepatotoxic and nontoxic drugs based on in vitro covalent binding data; however, the approach still would falsely identify some agents as potentially hepatotoxic.

Dry adsorbed emulsion of simvastatin: optimization and in vivo advantage.

In the present study, Simvastatin was incorporated in emulsion of soybean oil and propylene glycol monocaprylate as oily phase and Tween 80 and Cremophor EL as surfactants and also their mixtures. Dry adsorbed emulsions were prepared by using colloidal silicon dioxide in varying proportions to adsorb the liquid emulsion. Liquid emulsions were characterized for viscosity and mean globule size, and the dry adsorbed emulsions were evaluated for powder characteristics and reconstitution properties, dissolution profile, and for in vivo efficacy in rats. DSC and X-ray diffraction studies indicated complete amorphization and/or solubilization of Simvastatin in the dry adsorbed emulsion. It was supported by SEM studies, which did not show evidence of precipitation of the drug on the surface of the carrier. Dissolution studies revealed remarkable increase in dissolution of the drug compared to plain drug. One of the optimized formulations provided 10-fold enhancement in the dissolution compared to drug powder. After 24 hr of induction of hyperlipidemia in rats using poloxamer F127, administration of dry adsorbed emulsions effected significant reduction in the total cholesterol with levels of 439 mg/dL compared to 585 mg/dL of drug treated group (p < 0.01). Significant increase in the high-density lipoprotein levels were also observed after 4 days of treatment compare to positive control (p < 0.01).

Quantitative analysis of simvastatin and its beta-hydroxy acid in human plasma using automated liquid-liquid extraction based on 96-well plate format and liquid chromatography-tandem mass spectrometry.

An assay based on automated liquid-liquid extraction (LLE) and liquid chromatography-tandem mass spectrometry (LC/MS/MS) has been developed and validated for the quantitative analysis of simvastatin (SV) and its beta-hydroxy acid (SVA) in human plasma. A Packard MultiProbe II workstation was used to convert human plasma samples collected following administration of simvastatin and quality control (QC) samples from individual tubes into 96-well plate format. The workstation was also used to prepare calibration standards and spike internal standards. A Tomtec Quadra 96-channel liquid handling workstation was used to perform LLE based on 96-well plates including adding solvents, separating organic from aqueous layer and reconstitution. SV and SVA were separated through a Kromasil C18 column (50 mm x 2 mm i.d., 5 microm) and detected by tandem mass spectrometry with a TurboIonspray interface. Stable isotope-labeled SV and SVA, 13CD(3)-SV and 13 CD(3)-SVA, were used as the internal standards for SV and SVA, respectively. The automated procedures reduced the overall analytical time (96 samples) to 1/3 of that of manual LLE. Most importantly, an analyst spent only a fraction of time on the 96-well LLE. A limit of quantitation of 50 pg/ml was achieved for both SV and SVA. The interconversion between SV and SVA during the 96-well LLE was found to be negligible. The assay showed very good reproducibility, with intra- and inter-assay precision (%R.S.D.) of less than 7.5%, and accuracy of 98.7-102.3% of nominal values for both analytes. By using this method, sample throughput should be enhanced at least three-fold compared to that of the manual procedure.