Solubility Of Valsartan Research Articles

Preparation, characterization, in-vitro and toxicological evaluation of carbopol based nanogels for solubility enhancement of Valsartan

Solubility is an essential criterion for attaining desired concentration of the drug within the systemic circulation to ensure intended pharmacological action. The main setback for the formulation development of new chemical entities and generic drugs is their lower aqueous solubility. Therefore, a drug carrier system is needed which not only enhances the solubility of low aqueous soluble drugs but also maintains a constant pharmacological action of drugs within predetermined intervals of time. For this purpose, authors prepared carbopol 934-co-poly(itaconic acid) (CPcPIA) nanogels by the free radical polymerization technique for the solubility enhancement of Valsartan. The polymeric nanogels were characterized and studied for further evaluation. FTIR studies indicated no interactions between the drug and nanogel contents. SEM showed a porous and sponged structure of particles without any agglomeration. Similarly, higher thermal stability was detected for the fabricated nanogel compared to its constituents, while reduction in crystallinity of the drug and excipients was shown by XRD analysis, indicating the amorphous nature of the polymeric nanogels. Average particle size and zeta potential of prepared nanogels were found 290.32 nm and –8.32 mV, respectively. Furthermore, various studies such as sol-gel fraction, dynamic swelling, drug loading, in-vitro drug release studies, solubility, and toxicity study were conducted for the developed nanogels. A significant increase in the solubility of Valsartan (2.002, 2.976, and 3.543 mg/mL) was observed by polymeric nanogels in pH 1.2, deionized distilled water, and pH 7.4 as compared to reference product. Toxicity study indicated no toxic effect of prepared nanogels on rabbit's species. Thus, it can be demonstrated from the results that synthesized nanogels are not only limited to a specific class of drug but the solubility of all low aqueous soluble drugs can be enhanced by the prepared networks of nanogels.

Determination of valsartan solubility in supercritical carbon dioxide: Experimental measurement and molecular dynamics simulation

In this study, the solubility of valsartan in supercritical carbon dioxide (SC-CO2) was determined using a static method. The experimental data were measured under a limited range of pressures from 12 to 24MPa and at three different temperatures of 308.15, 318.15 and 328.15K. Furthermore, the effect of pressure and temperature on solute solubility was studied and discussed. Subsequently, the OPLS all-atom force field was applied to predict the free energy of solvation and solubility of valsartan in SC-CO2. To this purpose, the unknown parameters of the OPLS all-atom force field for valsartan were determined using quantum mechanics method and Nelder-Mead optimization algorithm. EPM2 model was used for CO2 molecules. In order to study the molecular interactions between the solute and the solvent, the contribution of electrostatic and Lennard-Jones interactions to the free energy of solvation was determined as a function of pressure at different temperatures. The results showed that, with increasing the pressure, the contribution of electrostatic interactions to the free energy of solvation decreased constantly close to linear shape. Moreover, with increasing the pressure, the contribution of Lennard-Jones interactions to the free energy of solvation decreased until reaching a minimum point; with a further increase in pressure, CO2 density increased and the contribution of repulsive part of Lennard-Jones potential becomes important, therefore, the continuation of the solvation process had become difficult. On the contrary, due to increase in the chemical potential of the solute, the solubility further increases. The calculated free energy of solvation was used for determining the solubility of valsartan over the studied range. The results of simulation were in a good agreement with the experimental data and the solubility behavior was well predicted at different temperatures and pressures. In this study, the value of 15.33% was obtained for Absolute Average Relative Deviation (AARD) between the experimental data and the simulation results.

Formulation of Gastro-retentive Floating Tablets of Valsartan by 2 power 2 Factorial Designs: In vitro and In vivo Evaluations

An oral dosage form containing gastro-retentive floating tablets forms a stomach-specific drug delivery system for the treatment of hypertension. Valsartan belongs to the BCS class II (poo Classification System). It is desirable to improve the extent of bioavailability (23%). The objective of the present study was to apply design of experiment to optimize floating drug delivery of valsartan by employing 22 factorial design. Improvement of the aqueous solubility of valsartan was done by solid dispersions using hot melt extrusion technique. Plasdone S630 copovidone is a variable carrier and drug to carrier ratio of 1:2 was optimized. Valsartan floating tablets were prepared by employing factorial design (22), where HPMC K15M (X1) and pregelatinized starch (X2) were independent variables and drug dissolution was the dependent parameter (Y1) to prepare matrix tablets. The factorial analysis, steepest ascent method was utilized for obtaining optimized formulation. In vitro evaluation, In vivo radiographic study and biopharmaceutical analysis in rabbits for valsartan optimized formulation (FT-5). Floating lag time (FLT) for valsartan optimized formulation (FT-5) was 15 s and total floating time (TFT) of the tablets was about 33 h, which was satisfactory. A four-point (1 h, 4 h, 8 h and 16 h) dissolution analysis gave satisfactory dissolution profile up to 24 h. The release kinetics of valsartan optimized formulation (FT-5) followed zero order and the release mechanism was found to be Korsemeyer Peppas model, i.e. swelling type. The dissolution efficiency for valsartan floating tablets was 1190.89% against the marketed formulation of 39.77%. The accelerated stability profile of valsartan optimized formulation (FT-5) was evaluated in terms of drug content and percent cumulative dissolution of valsartan in 24 h, in a 6 months study. In vivo X-ray image study for valsartan optimized formulation (FT-5) indicated the presence of intact tablet up to 12 h in gastric region of rabbit. The biopharmaceutical analysis in rabbits was conducted for valsartan optimized formulation (FT-5). The HPLC method was established and validated for the in vivo analysis. The Cmax was 453.2 ng/mL compared to that of the marketed tablets (522.4 ng/mL). The mean residence time (MRT) for the valsartan optimized formulation (FT-5) was 14.82 h as against 4 h for marketed tablet. The relative bioavailability of valsartan optimized formulation (FT-5) was 650% higher than the marketed tablet. To overcome the poor bioavailability of valsartan, it was suitably modified using hot-melt extrusion for improving therapeutic outcome. In conclusion, gastro-retentive drug delivery system is an excellent approach for improving the bioavailability of valsartan. 

Microemulsion Transdermal Formulation for Simultaneous Delivery of Valsartan and Nifedipine: Formulation by Design.

The objective of the study was to optimize the proportion of different components for formulating oil in water microemulsion formulation meant for simultaneous transdermal delivery of two poorly soluble antihypertensive drugs. Surface response methodology of Box-Behnken design was utilized to evaluate the effect of two oils (Captex 500 - x1 and Capmul MCM - x2) and surfactant (Acrysol EL135 - x3) on response y1 (particle size), y2 (solubility of valsartan), and y3 (solubility of nifedipine). The important factors which significantly affected the responses were identified and validated using ANOVA. The model was diagnosed using normal plot of residuals and Box-Cox plot. The design revealed an inverse correlation between particle size and concentration of Capmul MCM and Acrysol EL 135. However, an increase in concentration of Captex 500 led to an increase in particle size of microemulsion. Solubility of valsartan decreased while that of nifedipine increased with increase in concentration of Captex 500. Capmul MCM played a significant role in increasing the solubility of valsartan. The effect of Acrysol EL 135 on solubility of both drugs, although significant, was only marginal as compared to that of Captex 500 and Capmul MCM. The optimized microemulsion was able to provide an enhancement ratio of 27.21 and 63.57-fold for valsartan and nifedipine, respectively, with respect to drug dispersion in aqueous surfactant system when evaluated for permeation studies. The current studies candidly suggest the scope of microemulsion systems for solubilizing as well as promoting the transport of both drugs across rat skin at an enhanced permeation rate.

Control of Drug Dissolution Rate from Film Dosage Forms Containing Valsartan.

Film dosage forms (FDs) containing valsartan (VST), a popular antihypertensive drug, were prepared using a casting method with sodium alginate and other polysaccharides as the film base. Drug dissolution profiles of the FDs were investigated in limited medium. The FDs were 170–200 μm thick and were easy to handle. All FDs immediately swelled and disintegrated in the medium. About 23% of the VST incorporated into the FD prepared with 1.5% sodium alginate dissolved at 5 min. The initial dissolution rate of VST increased upon the addition of chitosan to the film base; this effect was not observed in the case of chitin. On the other hand, the rate apparently decreased upon modification with alginic acid. In addition, the solubility of VST in the dissolution medium was changed by the addition of chitosan or alginic acid. FDs prepared with polysaccharides are useful for simplifying the administration of drugs to patients, and the drug dissolution rate from FDs can be controlled by modification.

Experimental and thermodynamic analysis on the solubility of valsartan in ethyl acetate + (butanone, isopropyl ether) binary solvent mixtures (from 278.15 to 323.15 K)

ABSTRACTThe solubility of valsartan in ethyl acetate + (butanone, isopropyl ether) binary solvent mixtures was measured at temperatures T = 278.15–323.15 K and pressure p = 0.1 MPa with a laser monitoring dynamic technique by a synthetic method. The experimental data were regressed by the modified Apelblat equation, the general single model and the hybrid model. The experimental data are well correlated with the above models because the mean deviations (MDs) are less than 3.79%. The mole fraction solubility of valsartan increases with increase in temperature and enrichment in butanone content, while it decreases with increased mole fraction of isopropyl ether at constant temperature. In addition, thermodynamic studies, including Gibbs energy, entropy and enthalpy, were calculated by van’t Hoff analysis. The results showed that the dissolution of valsartan in mixed solvents is endothermic, spontaneous and entropy-driven.

Preparation and evaluation of valsartan by a novel semi-solid self-microemulsifying delivery system using Gelucire 44/14

The aim of the present study was to develop a novel semi-solid self-microemulsifying drug delivery system (SMEDDS) using Gelucire® 44/14 as oil with strong solid character to improve the oral bioavailability of poorly soluble drug valsartan. The solubility of valsartan in various excipients was determined, the pseudo-ternary phase diagram was constructed in order to screen the optimal excipients, and DSC analysis was performed to evaluate the melting point of SMEDDS. The optimal drug-loaded SMEDDS formulation was consisted of 30% Gelucire® 44/14 (oil), 40% Solutol® HS 15 (surfactant), and 30% Transcutol® P (cosurfactant) (w/w) with 80 mg valsartan/g excipients. The average droplet sizes of the optimized blank and drug-loaded SMEDDS formulations were 26.20 ± 1.43 and 33.34 ± 2.15 nm, and the melting points of them were 35.6 and 36.8 °C, respectively. The in vitro dissolution rate of optimal semi-solid SMEDDS was increased compared with commercial capsules, resulting in the 2.72-fold and 2.97-fold enhancement of Cmax and AUC0–t after oral administration in rats, respectively. These results indicated that the novel semi-solid SMEDDS formulation could potentially improve the oral bioavailability of valsartan, and the semi-solid SMEDDS was a desirable system than the traditional liquid SMEDDS because it was convenient for preparation, storage and transportation due to semi-solid state at room temperature and melted state at body temperature.

Development and optimization of press coated tablets of release engineered valsartan for pulsatile delivery

The present work is aimed to develop and optimize pulsatile delivery during dissolution of an improved formulation of valsartan to coordinate the drug release with circadian rhythm. Preliminary studies suggested that β cyclodextrin could improve the solubility of valsartan and showed AL type solubility curve. A 1:1 stoichiometric ratio of valsartan to β cyclodextrin was revealed from phase solubility studies and Job’s plot. The prepared complex showed significantly better dissolution efficiency (p < 0.05) compared to pure drug, which could be due to the formation of inclusion complex as revealed from FTIR and DSC studies. Continuous dissolution-absorption studies revealed that absorption of drug from valsartan β cyclodextrin complex was significantly higher (p < 0.05) compared to pure drug, in second part press-coated tablets of valsartan β cyclodextrin complex were subsequently prepared and application of the Plackett–Burman screening design revealed that HPMC K4M and EC showed significant effect on lag time. A 32 full factorial design was used to measure the response of HPMC K4M and EC on lag time and time taken for 90% drug release (T90). The optimized batch prepared according to the levels obtained from the desirability function had a lag time of 6 h and consisted of HPMC K4M:ethylcellulose in a 1:1.5 ratio with 180 mg of coating and revealed a close agreement between observed and predicted value (R2 = 0.9694).

Preparation and Bioavailability Assessment of SMEDDS Containing Valsartan

A self-microemulsifying drug delivery system (SMEDDS) has been developed to enhance diffusion rate and oral bioavailability of valsartan. The solubility of valsartan was checked in different oils, surfactants, and cosurfactants and ternary phase diagrams were constructed to evaluate the microemulsion domain. The valsartan SMEDDS was prepared using Capmul MCM (oil), Tween 80 (surfactant), and polyethylene glycol 400 (cosurfactant). The particle size distribution, zeta potential, and polydispersity index were determined and were found to be 12.3 nm, -0.746, and 0.138, respectively. Diffusion rate of valsartan was measured by in vitro dialysis bag method using phosphate buffer pH 6.8 as diffusion media. Developed high-performance liquid chromatography method was used to determine drug content in diffusion media. Oral bioavailability of valsartan SMEDDS was checked by using rabbit model. Results of diffusion rate and oral bioavailability of valsartan SMEDDS were compared with those of pure drug solution and of marketed formulation. Diffusion of valsartan SMEDDS showed maximum drug release when compared to pure drug solution and marketed formulation. The area under curve and time showed significant improvement as the values obtained were 607 ng h/mL and 1 h for SMEDDS in comparison to 445.36 and 1.36 h for market formulation suggesting significant increase (p < 0.01) in oral bioavailability of valsartan SMEDDS.

Solubility of Valsartan in Ethyl Acetate + Hexane Binary Mixtures from (278.15 to 313.15) K

The solubility of valsartan in ethyl acetate + hexane binary mixtures was measured by a synthetic method over the temperature range from (278.15 to 313.15) K at atmosphere pressure. The results show that the solubility of valsartan increases with increasing temperature and the increasing mole fraction of ethyl acetate of the binary mixtures. The experimental data were correlated using the modified Apelblat model, and the agreement with the experimental data was very good.

Solubility of Valsartan in Different Organic Solvents and Ethanol + Water Binary Mixtures from (278.15 to 313.15) K

The solubility of valsartan in pure methyl acetate, n-butyl acetate, acetonitrile, N,N-dimethylformamide, dichloromethane, chloroform, and ethanol + water binary mixtures was measured by a synthetic method over the temperature range (278.15 to 313.15) K at atmospheric pressure. The results show that the solubility of valsartan increases with increasing temperature in all six pure solvents and ethanol + water binary mixtures, and it increases with increasing mole fraction of ethanol in the binary mixtures. The experimental data were correlated using the modified Apelblat model, and the agreement with the experimental data was very good.