Powder Compaction: Compression Properties of Cellulose Ethers

Effective development of matrix tablets requires a comprehensive understanding of different raw material attributes and their impact on process parameters. Cellulose ethers (CE) are the most commonly used pharmaceutical excipients in the fabrication of hydrophilic matrices. The innate good compression and binding properties of CE enable matrices to be prepared using economical direct compression (DC) techniques. However, DC is sensitive to raw material attributes, thus, impacting the compaction process. This article critically reviews prior knowledge on the mechanism of powder compaction and the compression properties of cellulose ethers, giving timely insight into new developments in this field

A proton magnetic resonance study of the system: Di-(2-Ethylhexyl) Sodium Sulfosuccinate--water-n-Octane

Proton magnetic resonance (pmr) has proved to be a useful technique for following the behavior of water in the complex equilibria produced when water is added to solutions of di-(2-ethylhexyl)sodium sulfosuccinate, (Aerosol OT), in n-octane. This system passes through several clear and turbid phase transitions as water content is increased. On the basis of the appearance and location of water proton peaks in the various phases as compared to bulk water, it was possible to differentiate between solubilized and separated water and to draw some conclusions as to the participation of water in these phase transitions.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/33115/1/0000501.pd

Kinetic analysis of the hydrolysis of lecithin monolayers by phospholipase A

Enzymic hydrolysis by pancreatic phospholipase A (E.C. 3.1.1.4) of L-dioctanoyl-, L-didecanoyl- and L-didodecanoyllecithin monolayers was studied under constant surface pressure by measuring the amount of substrate which disappears per unit area per unit time. The reaction is first-order with respect to the total number of substrate molecules allowing the determination of a rate constant. Apparent limitations of the monolayer techniques are often caused by diffusion problems. Experimental conditions are discussed to detect and control these difficulties. pH dependence and calcium requirements of the enzymatic reaction are similar under monolayer and bulk conditions. For all three substrates plots of velocity vs. surface pressure show bell-shaped curves with a similar maximum rate at a surface pressure of about 8 dynes/cm. This result is discussed in relation to conformational changes in the lecithin molecules. With the monolayer techniques one can determine only a minimal specific activity, because of the unknown amount of enzyme involved in the catalysis. This minimal specific activity is compared with the value obtained with lecithin micelles as substrate in similar bulk conditions. Inhibition of the enzyme by competitive inhibitors present in mixed films cannot be studied by the monolayer technique. Comparison of the monolayer and bulk methods showed that both techniques are complementary

Practical Considerations in the Measurement of the Internal Relative Humidity of Pharmaceutical Packages with Data Loggers

The utility of temperature/humidity data loggers are evaluated as a low-cost approach to enrich practical understanding of the actual time dependent humidity that a pharmaceutical product is exposed to. While this approach is found to have significant utility in general, small systematic biases in the measurements due to the presence of the data logger are observed. Taking these biases into account enables more productive extrapolation of measured time/humidity profiles

Studies on the interaction of water with ethylcellulose: Effect of polymer particle size

The purpose of this research was to investigate the interaction of water with ethylcellulose samples and assess the effect of particle size on the interaction. The distribution of water within coarse particle ethylcellulose (CPEC; average particle size 310 μm) and fine particle ethylcellulose (FPEC; average particle size 9.7 μm) of 7 cps viscosity grade was assessed by differential scanning calorimetry (DSC) and dynamic vapor sorption analysis. The amounts of nonfreezing and freezing water in hydrated samples were determined from melting endotherms obtained by DSC. An increase in water content resulted in an increase in the enthalpy of fusion of water for the two particle size fractions of EC. The amount of nonfreezable water was not affected by the change in particle size at low water contents. Exposure of ethylcellulose to water for 30 minutes is sufficient to achieve equilibration within the hydrated polymer at 47% wt/wt water content. The moisture sorption profiles were analyzed according to the Guggenheim-Anderson-de Boer (GAB) and Young and Nelson equations, which can help to distinguish moisture distribution in different physical forms. The amount of externally adsorbed moisture was greater in the case of FPEC. Internally absorbed moisture was evident only with the CPEC. In light of these results, and explanation is offered for the success of FPEC in wet-granulation methods where CPEC was not successful

Solubilization of water by dialkyl sodium sulfosuccinates in hydrocarbon solutions

The apparent solubilization of water in hydrocarbon solvents by the addition of 0.1% to 2.0% w/w di-(2-ethylhexyl) sodium sulfosuccinate (AOT) has been studied. In n-octane and n-decane, transitions of clear-turbid-clear-turbid were observed with increasing water content, whereas in dodecane, tetradecane, hexadecane, cyclohexane, and toluene only one clear-turbid transition was seen. Separation of the first turbid region in n-octane and n-decane gave two clear phases. Direct analysis indicates a hydrocarbon phase containing surfactant-solubilized water and an aqueous phase containing some surfactant. Increasing amounts of water partition between these phases until a second clear region appears. Separation of phases in the second turbid region in n-octane and n-decane and in the turbid region of the other solvents produces a pure hydrocarbon phase and a phase containing a complex aggregate of AOT/water/hydrocarbon. Solubilization of water in n-octane solutions of di-(n-octyl) sodium sulfosuccinate and di-(n-hexyl) sodium sulfosuccinate is greatly reduced when compared to AOT. This suggests a significant effect due to the ethyl side chain in the AOT molecule.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/33042/1/0000428.pd