Solubility of antipsychotic drug risperidone in Transcutol+water co-solvent mixtures at 298.15 to 333.15K

Solubility Prediction of Drugs in Binary Solvent Mixtures at Various Temperatures Using a Minimum Number of Experimental Data Points

This study aimed to provide a rational experimental design to collect a minimum number of experimental data points for a drug dissolved in a given binary solvent mixture at various temperatures, and to describe a computational procedure to predict the solubility of the drugs in any solvent composition and temperature of interest. We gathered available solubility data sets from papers published from 2012 to 2016 (56 data sets, 3488 data points totally). The mean percentage deviations (MPD) used to check the accuracy of predictions was calculated by Eq. 10. Fifty-six datasets were analyzed using 8 training data points which the overall MPD was calculated to be 15.5% ± 15.1%, and for 52 datasets after excluding 5 outlier sets was 12.1% ± 8.9%. The paired t test was conducted to compare the MPD values obtained from the models trained by 7 and 8 training data points and the reduction in prediction overall MPD (from 17.7% to 15.5%) was statistically significant (p < 0.04). To further reduction in MPD values, the computations were also conducted using 9 training data points, which did not reveal any significant difference comparing to the predictions using 8 training data points (p > 0.88). This observation revealed that the model adequately trained using 8 data points and could be used as a practical strategy for predicting the solubility of drugs in binary solvent mixtures at various temperatures with acceptable prediction error and using minimum experimental efforts. These sorts of predictions are highly in demand in the pharmaceutical industry.

Nanocrystal-based drug delivery system of risperidone: lyophilization and characterization

OBJECTIVE

In the present work nanocrystal-based formulation of risperidone (RIS) was proposed to overcome solubility issue of RIS, while lyophilization technique was used effectively, for conversion of RIS nanosuspension to solid state.

SIGNIFICANCE

RIS nanosuspension was developed and stabilized with a combination of polycaprolactone and Pluronic^® F-68 as stabilizers. With focus on critical parameters like nature of cryoprotectants and effect of eutectic temperature on properties of nanosuspension, the suitability of lyophilization technique in improving the physical stability of prepared nanosuspension was also evaluated. Additionally, the developed nanocrystals were also assessed for their solid states properties.

METHODS

Various process parameters affecting average particle size and polydispersity index (PDI), viz. drug to surfactant ratio, solvent to anti-solvent ratio, stirring speed, type of stabilizer were optimized. Assessment of lyophilization as a suitable solidification technique (for conversion to powder form) was done with selective cryoprotectants (trehalose dihydrate and sorbitol).

RESULTS

The formulation was found to be stable at 4 °C for 3 months with size, PDI and zeta potential of 214 ± 3.4 nm, 0.120, and -10.2 ± 0.90 mV, respectively. Release profile of developed nanosuspension showed cumulative % release of ∼90% in initial 10 h whereas the value for the unprocessed drug was ∼11% in same time frame.

CONCLUSIONS

These findings suggest that developed formulation was able to enhance water solubility of the drug effectively and can be potentially used in the management of psychotic disorders.

Investigation of the effect of solubility increase at the main absorption site on bioavailability of BCS class II drug (risperidone) using liquisolid technique

BCS class II drugs usually suffer inadequate bioavailability as dissolution step is the absorption rate limiting step. In this work, the effect of solubility increase at the main absorption site for these drugs was investigated using risperidone as a drug model. Liquisolid technique was applied to prepare risperidone per-oral tablets of high dissolution rate at intestinal pH (6.8) using versatile nonionic surfactants of high solubilizing ability [Transcutol HP, Labrasol and Labrasol/Labrafil (1:1) mixture] as liquid vehicles at different drug concentrations (10-30%) and fixed (R). The prepared liquisolid tablets were fully evaluated and the dissolution rate at pH 6.8 was investigated. The formulae that showed significantly different release rate were selected and subjected to mathematical modeling using DE25, MDT and similarity factor (f2). Depending on mathematical modeling results, formula of higher dissolution rate was subjected to solid state characterization using differential scanning calorimetric (DSC), infrared spectroscopy (IR) and X-ray diffraction (XRD). Finally, the drug bioavailability was studied in comparison to conventional tablets in rabbits. Results showed that liquisolid tablet prepared using Labrasol/Labrafil (1:1) mixture as liquid vehicle containing 10% risperidone is a compatible formula with law drug crystallinity and higher dissolution rate (100% in 25 min). The drug bioavailability was significantly increased in comparison to the conventional tablets (1441.711 μg h/mL and 137.518 μg/mL in comparison to 321.011 μg h/mL and 38.673 μg/mL for AUC and Cpmax, respectively). This led to the conclusion that liquisolid technique was efficiently improved drug solubility and solubility increase of BCS class II drugs at their main absorption site significantly increases their bioavailability.

Dissolution thermodynamics and solubility of silymarin in PEG 400-water mixtures at different temperatures

An isothermal method was used to measure the solubility of silymarin in binary polyethylene glycol 400 (PEG 400) + water co-solvent mixtures at temperatures T = 298.15-333.15 K and pressure p = 0.1 MPa. Apelblat and Yalkowsky models were used to correlate experimental solubility data. The mole fraction solubility of silymarin was found to increase with increasing the temperature and mass fraction of PEG 400 in co-solvent mixtures. The root mean square deviations were observed in the range of 0.48-5.32% and 1.50-9.65% for the Apelblat equation and Yalkowsky model, respectively. The highest and lowest mole fraction solubility of silymarin was observed in pure PEG 400 (0.243 at 298.15 K) and water (1.46 × 10(-5) at 298.15 K). Finally, thermodynamic parameters were determined by Van't Hoff and Krug analysis, which indicated an endothermic and spontaneous dissolution of silymarin in all co-solvent mixtures.