Comparison of the liquisolid technique and co-milling for loading of a poorly soluble drug in inorganic porous excipients.

Drug loading into mesoporous carriers may help to improve the dissolution of poorly aqueous-soluble drugs. However, both preparation method and carrier properties influence loading efficiency and drug release. Accordingly, this study aimed to compare two preparation methods: formulation into liquisolid systems (LSS) and co-milling for their efficiency in loading the poorly soluble model drug cyclosporine A (CyA) into mesoporous magnesium aluminometasilicate Neusilin® US2 (NEU) or functionalized calcium carbonate (FCC). Scanning electron microscopy was used to visualize the morphology of the samples and evaluate the changes that occurred during the drug loading process. The solid-state characteristics and physical stability of the formulations, prepared at different drug concentrations, were determined using X-ray powder diffraction. In vitro release of the drug was evaluated in biorelevant media simulating intestinal fluid. The obtained results revealed improved drug release profiles of the formulations when compared to the milled (amorphous) CyA alone. The dissolution of CyA from LSS was faster in comparison to the co-milled formulations. Higher drug release was achieved from NEU than FCC formulations presumably due to the higher pore volume and larger surface area of NEU.

Flow Equations for Free-Flowable Particle Fractions of Sorbitol for Direct Compression: An Exploratory Multiple Regression Analysis of Particle and Orifice Size Influence.

Flowability is among the most important properties of powders, especially when fine particle size fractions need to be processed. In this study, our goal was to find a possibly simple but accurate mathematical model for predicting the mass flow rate for different fractions of the pharmaceutical excipient sorbitol for direct compression. Various regression models derived from the Jones-Pilpel equation for the prediction of the mass flow rate were investigated. Using validation with experimental data for various particle and hopper orifice sizes, we focused on the prediction accuracy of the respective models, i.e., on the relative difference between measured and model-predicted values. Classical indicators of regression quality from statistics were addressed as well, but we consider high prediction accuracy to be particularly important for industrial processing in practice. For individual particle size fractions, the best results (an average prediction accuracy of 3.8%) were obtained using simple regression on orifice size. However, for higher accuracy (3.1%) in a unifying model, valid in the broad particle size range 0.100-0.346 mm, a fully quadratic model, incorporating interaction between particle and orifice size, appears to be most appropriate.

Mechanistic study of dissolution enhancement by interactive mixtures of chitosan with meloxicam as model.

To enhance dissolution rate of meloxicam (MX), a poorly soluble model drug, a natural polysaccharide excipient chitosan (CH) is employed in this work as a carrier to prepare binary interactive mixtures by either mixing or co-milling techniques. The MX-CH mixtures of three different drug loads were characterized for morphological, granulometric, and thermal properties as well as drug crystallinity. The relative dissolution rate of MX was determined in phosphate buffer of pH 6.8 using the USP-4 apparatus; a significant increase in MX dissolution rate was observed for both mixed and co-milled mixtures comparing to the raw drug. Higher dissolution rate of MX was evidently connected to surface activation by mixing or milling, which was pronounced by the higher specific surface energy as detected by inverse gas chromatography. In addition to the particle size reduction, the carrier effect of the CH was confirmed for co-milling by linear regression between the MX maximum relative dissolution rate and the total surface area of the mixture (R2 = 0.863). No MX amorphization or crystalline structure change were detected. The work of adhesion/cohesion ratio of 0.9 supports the existence of preferential adherence of MX to the coarse particles of CH to form stable interactive mixtures.

Systematic Study of the Effects of High Shear Granulation Parameters on Process Yield, Granule Size, and Shape by Dynamic Image Analysis.

The aim of the work was to analyze the influence of process parameters of high shear granulation on the process yield and on the morphology of granules on the basis of dynamic image analysis. The amount of added granulation liquid had a significant effect on all monitored granulometric parameters and caused significant changes in the yield of the process. In regard of the shape, the most spherical granules with the smoothest surface were formed at a liquid to solid ratio of ≈1. The smallest granules were formed at an impeller speed of 700 rpm, but the granules formed at 500 rpm showed both the most desirable shape and the highest process yield. Variation in the shape factors relied not only on the process parameters, but also on the area equivalent diameter of the individual granules in the batch. A linear relationship was found between the amount of granulation liquid and the compressibility of the granules. Using response surface methodology, models for predicting the size of granules and process yield related to the amount of added liquid and the impeller speed were generated, on the basis of which the size of granules and yield can be determined with great accuracy.

Comparison of Flow and Compression Properties of Four Lactose-Based Co-Processed Excipients: Cellactose® 80, CombiLac®, MicroceLac® 100, and StarLac®.

The utilization of co-processed excipients (CPEs) represents a novel approach to the preparation of orally disintegrating tablets by direct compression. Flow, consolidation, and compression properties of four lactose-based CPEs-Cellactose® 80, CombiLac®, MicroceLac® 100, and StarLac®-were investigated using different methods, including granulometry, powder rheometry, and tablet compaction under three pressures. Due to the similar composition and the same preparation technique (spray drying), the properties of CPEs and their compacts were generally comparable. The most pronounced differences were observed in flowability, undissolved fraction after 3 min and 24 h, energy of plastic deformation (E2), ejection force, consolidation behavior, and compact friability. Cellactose® 80 exhibited the most pronounced consolidation behavior, the lowest values of ejection force, and high friability of compacts. CombiLac® showed excellent flow properties but insufficient friability, except for compacts prepared at the highest compression pressure (182 MPa). MicroceLac® 100 displayed the poorest flow properties, lower ejection forces, and the best mechanical resistance of compacts. StarLac® showed excellent flow properties, the lowest amounts of undissolved fraction, the highest ejection force values, and the worst compact mechanical resistance. The obtained results revealed that higher compression pressures need to be used or further excipients have to be added to all tested materials in order to improve the friability and tensile strength of formed tablets, except for MicroceLac® 100.

Systematic study of paracetamol powder mixtures and granules tabletability: Key role of rheological properties and dynamic image analysis.

The aim of this systematic study was to analyze the granulometric and rheological behavior of tableting mixtures in relation to tabletability by single tablet and lab-scale batch compression with an eccentric tablet machine. Three mixtures containing 33, 50, and 66% of the cohesive drug paracetamol were prepared. The high compressibility of the powder mixtures caused problems with overcompaction or lamination in the single tablet compression method; due to jamming of the material during the filling of the die, the lab-scale batch compression was impossible. Using high shear granulation, the flow properties and tabletability were adjusted. A linear relationship between the span of granules and the specific energy measured by FT4 powder rheometer was detected. In parallel, a linear relationship between conditioned bulk density and the tensile strength of the tablets at lab-scale batch tableting was noted. The combination of dynamic image analysis and powder rheometry was useful for predicting the tabletability of pharmaceutical mixtures during the single tablet (design) compression and the lab-scale batch compression.

The importance of the coating material type and amount in the preparation of liquisolid systems based on magnesium aluminometasilicate carrier.

Albeit the preparation of liquisolid systems represents an innovative approach to enhance the dissolution of poorly soluble drugs, their broader utilization is still limited mainly due to the problematic conversion of the liquid into freely flowing and readily compressible powder. Accordingly, the presented study aims to determine the optimal carrier/coating material ratio (R value) for formulations based on magnesium aluminometasilicate (NUS2) loaded with polyethylene glycol 400. Four commercially available colloidal silica were used as coating materials in nine different R values (range of 5 - 100). The obtained results suggested that the higher R value leads to the superior properties of powder mixtures, such as better flowability, as well as compacts with higher tensile strength and lower friability. Moreover, it was observed that the type of coating material impacts the properties of liquisolid systems due to the different arrangement of particles in the liquisolid mixture. To confirm the noted dependency of R value and coating material type, the one- and two-way ANOVA, linear regression and principal component analysis (PCA) techniques were performed. In addition, a comparison of results with the properties of loaded NUS2 itself revealed that LSS with sufficient properties may be prepared even without the coating material.

Relevance of the theoretical critical pore radius in mesoporous silica for fast crystallizing drugs.

Formulation of poorly water-soluble drugs with mesoporous silica has become a thriving field of pharmaceutics. The theoretical critical pore diameter has been introduced as a maximum value below which an undesired drug crystallization is suppressed by spatial confinement. Currently, only few values have been reported and study of fast crystallising drugs is missing especially at relevant storage temperatures. This study investigated the critical pore diameter of three model drugs with a poor glass-forming ability (i.e. haloperidol, carbamazepine and benzamide) using different mesoporous carriers (Parteck® SLC 500, Neusilin® US2, Syloid® XDP 3050 and Aeroperl® 300 Pharma) and subsequently monitored physical formulation stability over three months by X-ray powder diffraction. The selected drugs showed clear differences in their estimated critical pore diameters, whereas a temperature dependence was barely relevant for pharmaceutical storage conditions. Superior stability was noted for the formulations containing benzamide in line with its predicted relatively large critical pore diameter of 29.5 nm. Contrarily, impaired physical stability depending on drug loading was observed in the case of haloperidol representing a compound with a rather small critical pore diameter (8.4 nm). These findings confirm the importance of estimating the critical pore diameter, especially for poor glass-forming drugs.

Mechanistic aspects of drug loading in liquisolid systems with hydrophilic lipid-based mixtures.

Despite the increasing interest in pharmaceutical use of mesoporous silica, there is still only limited knowledge on mechanisms of pore loading and subsequent drug desorption and release. Hence the aim of this work was to address the mechanistic aspects of drug loading into the mesoporous silica pores and to minimise the risk of pore clogging. Hydrophilic solvents (polysorbate 20 and polyethylene glycol 200) with high dissolving capacity for the model drug celecoxib were studied for their surface tension as well as dynamic viscosity by considering hydration. As an innovation in liquisolid systems preparation, a rather simple drug loading method on a mesoporous carrier was introduced by using semi-volatile solvent mixtures. Fast liquid loading into the pores was achieved due to the lowered viscosity and surface tension of the whole solvent system. Drug release kinetics suggested that lipid-based formulations belonging to class IV of Lipid Formulation Classification System may exhibit a lower risk of incomplete desorption from a carrier. The utilisation of volatile solvents during preparation had no negative impact on the liquisolid systems' dissolution behaviour. All prepared formulations showed similar significantly faster dissolution profiles compared to the physical mixture. The novel approach has potential to promote liquisolid applications in pharmaceutics.

Furosemide ethanol-free oral solutions for paediatric use: formulation, HPLC method and stability study.

BACKGROUND: Oral liquid solutions of the diuretic active ingredient furosemide (FUR) marketed across Europe do not comply with recent requirements for paediatric preparation owing to their ethanol content and, moreover, in some countries only tablet or injection dosage forms of furosemide are available. OBJECTIVES: To formulate extemporaneous paediatric ethanol-free solutions of FUR (2 mg/mL) with suitable solubility in the aqueous vehicle and an acceptable taste and to evaluate their stability under two different storage conditions during a 9-month study period. METHODS: Our work presents two developed formulations of FUR ethanol-free paediatric oral solutions 2 mg/mL for easy extemporaneous compounding in a pharmacy. FUR solubility avoiding the use of ethanol was achieved using sodium hydroxide (formulation F1) or disodium hydrogen phosphate dodecahydrate (formulation F2). The preparations were stored at 25°C±3°C or at 40°C±0.5°C and protected from light. For FUR and preservative, methylparaben (MP), a stability assay was conducted by a high-performance liquid chromatography validated method and determination of pH stability. RESULTS: The remaining FUR concentration was >90% of the initial concentration after 270 days in both formulations at both storage conditions, 25°C and 40°C. The concentration of MP decreased significantly in the formulation F2 stored at 40°C. CONCLUSIONS: Both formulations were stable when stored at room temperature for up to 9 months; formulation F1 was stable even at 40°C. MP used as an antimicrobial agent fully satisfied the recommended criteria for preservative efficacy in oral preparations according to the European Pharmacopoeia 9.0 (5.1.3).

The influence of stevia on the flow, shear and compression behavior of sorbitol, a pharmaceutical excipient for direct compression.

Good flow and compaction properties are necessary for the manipulation of particulate material in the pharmaceutical industry. The influence of the addition of an alternative sweetener, rebaudioside A, in a concentration 0.2% w/w and 0.5% w/w on the flow, shear and compaction properties of sorbitol for direct compaction, Merisorb® 200, was investigated in this work. Rebaudioside A worsened the flow properties of sorbitol: the Hausner ratio, the compressibility index and the mass flow rate through the aperture of a model hopper. Using a Jenike shear cell revealed a significant increase in cohesion leading to the decrease of the flow function; moreover, the addition of rebaudioside A increased the total energy for compression of tablets and plasticity estimated by the force-displacement method. Finally, the tablets showed a higher tensile strength and needed longer time to disintegrate compared to the tablets made of sorbitol itself. In view of the results for the free-flowable excipient, sorbitol, the effects of stevia even for a 0.2% w/w concentration have to be carefully considered, particularly whenever used in pharmaceutical formulations of poor flow properties.

Fractal aspects of the flow and shear behaviour of free-flowable particle size fractions of pharmaceutical directly compressible excipient sorbitol.

Flowability of powder excipients is directly influenced by their size and shape although the granulometric influence of the flow and shear behaviour of particulate matter is not studied frequently. In this work, the influence of particle size on the mass flow rate through the orifice of a conical hopper, and the cohesion and flow function was studied for four free-flowable size fractions of sorbitol for direct compression in the range of 0.080-0.400 mm. The particles were granulometricaly characterized using an optical microscopy; a boundary fractal dimension of 1.066 was estimated for regular sorbitol particles. In the particle size range studied, a non-linear relationship between the mean particle size and the mass flow rate Q10 (g/s) was detected having amaximum at the 0.245mm fraction. The best flow properties of this fraction were verified with aJenike shear tester due to the highest value of flow function and the lowest value of the cohesion. The results of this work show the importance of the right choice of the excipient particle size to achieve the best flow behaviour of particulate material.Key words: flowability size fraction sorbitol for direct compaction Jenike shear tester fractal dimension.

Extemporaneous sotalol hydrochloride oral solutions for use in paediatric cardiology: formulation and stability study.

OBJECTIVES: Sotalol hydrochloride (SOT) is an antiarrhythmic ß-blocker which is highly effective for the treatment of supraventricular tachycardia in children. However, a licensed paediatric dosage form with sotalol is not currently available in Europe. The aim of this work was to formulate paediatric oral solutions with SOT 5 mg/mL for extemporaneous preparation in a hospital pharmacy with the lowest possible amount of excipients and to determine their stability. METHODS: Three aqueous solutions were formulated. One preparation without any additives for neonates and two preparations for children from 1 month of age were compounded using citric acid to stabilise the pH value, potassium sorbate 0.1% w/v as a preservative, and simple syrup or sodium saccharin as a sweetener. The samples were stored at room temperature and in a refrigerator, respectively, and the content of SOT and potassium sorbate was determined simultaneously using a validated high performance liquid chromatography method at different time points over 180 days. RESULTS: At least 95% of the initial sotalol concentration remained throughout the 180-day study period in all three preparations at both temperatures. The content of potassium sorbate decreased by 17% with sodium saccharin stored at room temperature. CONCLUSIONS: The three proposed oral aqueous solutions of SOT for neonates and infants were stable for 180 days. Storage in a refrigerator is preferred, particularly with sodium saccharin. The additive-free solution of SOT can be autoclaved to ensure microbiological stability and used particularly for neonates and in emergency situations.

Sampling times influence the estimate of parameters in the Weibull dissolution model.

The aim is to determine how well the parameters of the Weibull model of dissolution can be estimated in dependency on the chosen times to measure the empirical data. The approach is based on the theory of Fisher information. We show that in order to obtain the best estimates the data should be collected at time instants when tablets actively dissolve or at their close proximity. This is in a sharp contrast with commonly used experimental protocols when sampling times are distributed rather uniformly.

The effect of the size of a conical hopper aperture on the parameters of the flow equation of sorbitol and its size fractions.

Determination of the rate of gravitational flow through a hopper aperture is one of the most widely used methods for the evaluation of flowability properties of pharmaceutical materials. This work studies the influence of the diameter of a conical hopper aperture in the range of 0.6-1.5 cm on the mass flow rate Q (g/s) of the pharmaceutical excipient, sorbitol, for direct compression (Merisorb 200, MS 200) and its size fractions in the range of 0.080-0.400 mm in order to recommend the appropriate aperture size for testing. Non-linear dependence of the flow rate on the aperture diameter is modeled by the Jones-Pilpel power equation. Using the actual parameters of the power equation, the precision of the mass flow rate prediction was the basic criterion in optimization of the orifice diameter. It was detected experimentally that for the evaluation of the flow rate of MS 200 and its size fractions in the range used a 1.0 cm aperture is recommended, which allows the most precise prediction of the flow rate.Key words: particulate material excipient, flow equation conical hopper size fraction.

Development of a gradient HPLC method for the simultaneous determination of sotalol and sorbate in oral liquid preparations using solid core stationary phase.

A selective and sensitive gradient HPLC-UV method for quantification of sotalol hydrochloride and potassium sorbate in five types of oral liquid preparations was developed and fully validated. The separation of an active substance sotalol hydrochloride, potassium sorbate (antimicrobial agent), and other substances (for taste and smell correction, etc.) was performed using an Ascentis Express C18 (100 × 4.6 mm, particles 2.7 µm) solid core HPLC column. Linear gradient elution mode with a flow rate of 1.3 mL min(-1) was used, and the injection volume was 5 µL. The UV/Vis absorbance detector was set to a wavelength of 237 nm, and the column oven was conditioned at 25°C. A sodium dihydrogen phosphate dihydrate solution (pH 2.5; 17.7 mM) was used as the mobile phase buffer. The total analysis time was 4.5 min (+2.5 min for reequilibration). The method was successfully employed in a stability evaluation of the developed formulations, which are now already being used in the therapy of arrhythmias in pediatric patients; the method is also suitable for general quality control, that is, not only just for extemporaneous preparations containing the mentioned substances.