Use of extrusion aids for successful production of Kollidon® CL-SF pellets by extrusion-spheronization.

OBJECTIVE: Fine particle ethylcellulose (FPEC) or poly(ethylene oxide) (PEO) addition to a Kollidon CL-SF was investigated to address low yield and poor sphericity in extruded-spheronized pellets. SIGNIFICANCE: The success of crospovidone as a diluent in extrusion-spheronization was dependent on a small particle size of the polymer. FPEC aided production of rugged and spherical pellets using a large particle size grade, Polyplasdone® XL. PEO acted as an extrusion-spheronization aid when ethylcellulose was the diluent. These extrusion-spheronization aids could serve in this role when Kollidon® CL-SF (K CL-SF) is the diluent. METHODS: The influence of formulation and process variables on pellet properties was investigated using design of experiments. A planetary mixer was used to prepare powder blends and the wetted mass after addition of water. An EXD 60 extruder produced extrudate that was spheronized in a Q230 marumerizer. Wet pellets were dried in a forced-air oven. RESULTS: FPEC improved rounding up but reduced pellet yield. Poly(ethylene oxide) imparted desired characteristics to the wetted mass, the extrudate, and the spheronized pellets. Pellet average diameter, yield, sphericity, aspect ratio, friability, and dissolution profile were assessed. Equations for pellet characteristics facilitated discussion of the influences of factors and their interactions. Optimization was performed on pellets that included PEO. CONCLUSIONS: PEO proved to be an exceptional extrusion-spheronization aid in the preparation of pellets using K CL-SF. It facilitated wetted mass extrusion with minimal mass loss to the extruder, and markedly improved the sphericity of the pellets produced by marumerization. Immediate release pellets were obtained.

Development and Characterization of Chitosan Cross-Linked With Tripolyphosphate as a Sustained Release Agent in Tablets, Part I: Design of Experiments and Optimization.

Certain issues with the use of particles of chitosan (Ch) cross-linked with tripolyphosphate (TPP) in sustained release formulations include inefficient drug loading, burst drug release, and incomplete drug release. Acetaminophen was added to Ch:TPP particles to test for advantages of drug addition extragranularly over drug addition made during cross-linking. The influences of Ch concentration, Ch:TPP ratio, temperature, ionic strength, and pH were assessed. Design of experiments allowed identification of factors and 2-factor interactions that have significant effects on average particle size and size distribution, yield, zeta potential, and true density of the particles, as well as drug release from the directly compressed tablets. Statistical model equations directed production of a control batch that minimized span, maximized yield, and targeted a t50 of 90 min (sample A); sample B that differed by targeting a t50 of 240-300 min to provide sustained release; and sample C that differed from sample B by maximizing span. Sample B maximized yield and provided its targeted t50 and the smallest average particle size, with the higher zeta potential and the lower span of samples B and C. Extragranular addition of a drug to Ch:TPP particles achieved 100% drug loading, eliminated a burst drug release, and can accomplish complete drug release.

A Quality by Experimental Design Approach to Assess the Effect of Formulation and Process Variables on the Extrusion and Spheronization of Drug-Loaded Pellets Containing Polyplasdone® XL-10.

Successful pellet production has been reported in literature with cross-linked poly(vinylpyrrolidone), Polyplasdone® XL-10 and INF-10. In the present study, a quality by experimental design approach was used to assess several formulation and process parameter effects on the characteristics of Polyplasdone® XL-10 pellets, including pellet size, shape, yield, usable yield, friability, and number of fines. The hypothesis is that design of experiments and appropriate data analysis allow optimization of the Polyplasdone product. High drug loading was achieved using caffeine, a moderately soluble drug to allow in vitro release studies. A five-factor, two-level, half-fractional factorial design (Resolution V) with center point batches allowed mathematical modeling of the influence of the factors and their two-factor interactions on five of the responses. The five factors were Polyplasdone® level in the powder blend, volume of water in the wet massing step, wet mixing time, spheronizer speed, and spheronization time. Each factor and/or its two-factor interaction with another factor influenced pellet characteristics. The behavior of these materials under various processing conditions and component levels during extrusion-spheronization have been assessed, discussed, and explained based on the results. Numerical optimization with a desirability of 0.974 was possible because curvature and lack of fit were not significant with any of the model equations. The values predicted by the optimization described well the observed responses. The hypothesis was thus supported.

Use of fine particle ethylcellulose as the diluent in the production of pellets by extrusion-spheronization.

The effect of small ethylcellulose particle size on the manufacture and properties of pellets produced by extrusion-spheronization was investigated. A factorial design revealed the effects of microcrystalline cellulose (MCC), polyethylene oxide (PEO), water, and spheronization speed and time on pellet properties. Response surface modeling allowed optimization of the responses with expansion to a central composite design. Pellet yield, size, shape, friability and drug release profile were studied, along with surface and interior morphology. Pellets were spherical irrespective of the formulation and process variables and exhibited physical and mechanical characteristics appropriate for further processing. Yield in the 12/20 mesh cut was lower with FPEC than observed with coarse particle ethylcellulose (CPEC), but FPEC-containing pellets were more rugged and the PEO to obtain optimal pellets was lower for FPEC compared to CPEC. Immediate release products were obtained and ethylcellulose particle size was of no consequence to drug release. Observed responses for the optimized product agreed with predicted values, demonstrating the success of the optimization procedure. These results suggest that FPEC is a good diluent for extrusion-spheronization.

Crospovidone interactions with water. II. Dynamic vapor sorption analysis of the effect of Polyplasdone particle size on its uptake and distribution of water.

Polyplasdone of different particle size was used to study the sorption, desorption, and distribution of water, and to seek evidence that larger particles can internalize water. The three samples were Polyplasdone® XL, XL-10, and INF-10. Moisture sorption and desorption isotherms at 25 °C at 5% intervals from 0 to 95% relative humidity (RH) were generated by dynamic vapor sorption analysis. The three products provided similar data, judged to be Type III with a small hysteresis that appears when RH is below 65%. An absent rounded knee in the sorption curve suggests that multilayers form before the monolayer is completed. The hysteresis indicates that internally absorbed moisture is trapped as the water is desorbed and the polymer sample shrinks, thus requiring a lower level of RH to continue desorption. The fit of the Guggenheim-Anderson-de Boer (GAB) and the Young and Nelson equations was accomplished in the data analysis. The W(m), C(G), and K values from GAB analysis are similar across the three samples, revealing 0.962 water molecules per repeating unit in the monolayer. A small amount of absorbed water is identified, but this is consistent across the three particle sizes.

Crospovidone interactions with water. I. Calorimetric study of the effect of Polyplasdone particle size on its uptake and distribution of water.

The ability of crospovidone to take up and distribute water in the polymer samples was studied using differential scanning calorimetry (DSC). Polyplasdone(®) is an example of crospovidone that, although insoluble in water, serves as a superdisintegrant. Three samples of Polyplasdone(®) with different mean particle size were studied to see the effect of particle size on the water uptake and distribution characteristics. Water was shown to plasticize Polyplasdone(®) samples by a reduction in the glass transition temperature as the water content was increased. Although the particle sizes covered a wide range, there was essentially no difference in the ability to take up or distribute water. Three types of water were observed, namely water closely associated with the polymer, water built up as multilayers, and bulk water. Although the water closely associated with the polymer could not be detected by DSC, it could be calculated by mass balance and by extrapolation of the data to the x-axis in a plot of freezable water content as a function of the actual water content. A split in the melting endotherm of water that freezes supported the premise of two forms of freezable water. The number of water molecules per repeating unit could be calculated.

Coated hydralazine hydrochloride beads for sustained release after oral administration.

Hydralazine hydrochloride is an antihypertensive used alone or in combination with isosorbide nitrate for the treatment of congestive heart failure. Since control of blood pressure should be continuous, sustained release delivery of this drug is considered therapeutically beneficial. Core beads for oral administration of this drug were prepared by extrusion-spheronization. Using experimental design to define the coat that was applied, the core beads were coated using a fluid bed coater to different coat thickness with combinations of two commercially available products dissolved in a hydroalcoholic solvent. The coat is a film with a combination of ethylcellulose and hydroxypropylcellulose that can provide desirable release profiles. Visually spherical and rugged bead products were obtained. Two products were identified that exhibited essentially a zero order release profile following a 2-h lag time with release of greater than 70% of the drug over the next 10 h in simulated intestinal fluid.

Use of coarse ethylcellulose and PEO in beads produced by extrusion-spheronization.

This study evaluated the potential of coarse ethylcellulose (CPEC) and high molecular weight polyethylene oxide (PEO) as excipients in the production of beads by extrusion-spheronization. CPEC was investigated as a diluent and PEO as an extrusion aid and a binder. Beads were manufactured with caffeine as a model drug. Release studies were conducted, and the bead size, shape, yield, and friability were determined. The effects of formulation and process variables and their interactions were studied by a sequential experimental design based on a response surface method. In the initial stage, a two level half fractional factorial design was employed as a screening design, which was subsequently augmented to a central composite design. Statistical analysis indicated that formulation variables including PEO content, microcrystalline cellulose (MCC) content, and water content, and two process variables, namely spheronizer speed and spheronization time, significantly affected the properties of the beads. Interactions between two factors have significant effects on several of the measured responses. Simultaneous optimization of the responses was conducted and validated by performing experiments at the optimal conditions. Overall, the results confirmed that immediate release, spherical beads with low friability and narrow size distribution could be produced with minimal amounts of MCC.

Effect of methyl branching of C8H18 alkanes and water activity on lipase-catalyzed enantioselective esterification of ibuprofen

The purpose of this research was to study the effect of the methyl branching of a high log P alkane solvent and the water activity in the organic medium on the initial rate and the enantioselectivity of ibuprofen esterification catalyzed by Candida rugosa lipase. Resolution of ibuprofen is important because S-(+)-ibuprofen has the desired pharmacological activity, whereas the R-(-)-enantiomer causes much of the side effects. The Candida rugosa lipase-catalyzed reaction in isooctane at 40ºC and 0.73 water activity gave the best results, both in terms of the initial reaction rate and the enantioselectivity of the reaction. An increase in water activity allowed a higher reaction rate and enantiomeric excess in each of the four solvents. An increase in methyl branching did not necessarily increase the initial reaction rate, but it allowed a higher enantioselectivity, evidenced by an increase in the substrate enantiomeric excess.

Extruded and spheronized beads containing Carbopol 974P to deliver nonelectrolytes and salts of weakly basic drugs.

The purpose of the study was to explore the utilization of Carbopol 974P, NF, resin in a bead dosage form manufactured by extrusion and spheronization. It was possible to prepare beads in this study by using calcium chloride to overcome the tack problem associated with wetted Carbopol 974P. The actives included both salts of weakly basic drugs (chlorpheniramine maleate and diphenhydramine hydrochloride) and nonelectrolytes (caffeine and dyphylline) which have a broad range of solubilities. Nonelectrolytes were released faster than the salts of weakly basic drugs. This is contrary to the behavior typically seen with a matrix system where the more soluble drug is released faster than a poorly soluble one. In the results of the present study, the solubility does not determine the drug release rate. Ionic interactions between the protonated amines of the salts and the carboxylates of the Carbopol resin are suggested to be the reason for the slower release of the salts of weakly basic drugs. Data from tack measurements confirm that this ionic interaction affects the behavior of the wetted Carbopol. In addition to the drug release profiles, bead average diameter, roundness, friability, and density were also determined.