Biomedical subjects

J W Mauger

Publications and source records attributed to J W Mauger.

8 recordsLinked to original sources

PubMed1979

Hydrodynamic characterization of a spin-filter dissolution device.

The spin-filter dissolution device was characterized using a two-dimensional convective diffusion model. Experimental model testing involved analysis of dissolution rates from nondisintegrating salicylic acid disks. The disks were prepared as double-layer tablets, with an ethylcellulose layer as a nondissolving surface. For each dissolution run, the disk was positioned so that the dissolving salicylic acid surface was parallel to the flow of the circulating fluid. Experimental variables included the stirring speed, the tablet radius, and the distance of the tablet from the stirring source. At the farthest distance from the stirring source, the average numerical exponents for stirring speed and tablet radius were 0.58 and 1.54, respectively, which compare favorably with the values of 0.50 and 1.50 from the model. When the dissolving salicylic acid surface was positioned closer to the stirring source, the numberical exponent for the stirring speed increased significantly, while the average numerical exponent for the tablet radius was lowered to 1.07, indicating a change is dissolution mechanism as a function of distance from the stirring source. These data indicate that dissolution rates are not necessarily proportional to surface area as predicted by the Nernst equation and that distance from the stirring source is significant.

Chemistry, Pharmaceutical↗

PubMed1979

Tablet position and basket type effects in spin-filter dissolution device.

The effects of stirring and basket placement on tablet dissolution using the previously developed Shah spin-filter device were investigated. Visualization of flow and dissolution patterns was possible by testing nondisintegrating colored tablets. Dissolution experiments were conducted on nondisintegrating double-layered tablets containing salicylic acid as the dissolving layer and ethylcellulose as an inert nondissolving layer. Visual observations revealed that color was drawn more rapidly from the tablet face resting on the bottom of the basket. Dissolution data from multilayered tablets revealed that when the salicylic acid face was resting on the bottom of the basket, the dissolution was appreciably more rapid than when it was facing up in the basket. This phenomenon was found for several stirring speeds.

Diffusion↗

PubMed1978

Thermodynamics of aqueous solutions of parabens.

The solubility of a related series of parabens was determined in water at four temperatures. The parabens chosen were the methyl through n-butyl p-hydroxybenzoates, and the temperature variations were 5 degrees increments from 25 to 40 degrees. These solutes are useful preservatives, especially combinations of the methyl and propyl ester derivatives. The chemical relationship of these compounds varied by successive linear methylene additions on the ester portion of the molecules. The thermodynamic values obtained for these aqueous systems could be related to these molecular variants since the remainder of the molecule was constant. For the overall thermodynamics, the free energy functions such as the ideal, actual, and excess were found to be smooth, nonlinear functions of the number of carbon atoms in the alkyl portion of the paraben esters. A linear relationship with the number of carbon atoms in the ester portion of these esters was found with the partial excess free energy of the solute.

Parabens↗

PubMed1978

Separation of multisized drug suspensions into narrow distributions by centrifugal elutriation.

A centrifugal elutriator rotor was used to separate suspensions of micronized hydrocortisone acetate and prednisolone acetate. Up to five distinct particle fractions could beisolated from a single parent suspension, and reasonable reproducibility was exhibited between various elutriator runs. Arithmetic means and associated standard deivations, based on volume, were calculated for each isolated fraction. These data demonstrate the narrowness and uniqueness of each fraction. The particle-size data show an apparent log-normal distribution for each isolate. The uniqueness of each fraction also was demonstrated by dissolution experiments where Fraction 1, the smallest fraction of prednisolone acetate, dissolved much more rapidly than Fraction 4, the largest fraction. The substantial difference in dissolution behavior of these two fractions of prednisolone acetate powder was biopharmaceutically significant.

Centrifugation↗

PubMed1977

Solubility profiles and thermodynamics of parabens in aliphatic alcohols.

The solubility of a series of compounds was determined in a wide polarity spectrum of normal aliphatic alcohols over a limited temperature range. The solutes chosen were the methyl through n-butyl p-hydroxybenzoates, several of these being useful preservatives. Solubility profiles were determined for these compounds, and the effect of temperature upon their solubility behavior was investigated. The solubility of the solutes is expressed in several concentration notations; mole fraction plots showed a variable twin peak array as a function of the dielectric constant for the solutes studied. Since heats of fusion were available and data were generated as a function of temperature, thermodynamic parameters for these systems could be calculated. The relationship of these parameters to multiple solubility peak array is discussed.

Alcohols↗

PubMed1977

Dissolution profile for multisized drug particles: new approximate expression.

New approximate expressions for the weight fraction undissolved were obtained using the Taylor series expansion. These approximations were tested using simulated data for multisized drug particle populations. The resulting calculations show that: (a) the approximations are not dependent on a knowledge of the analytical form of the particle-size density function, (b) the distribution effects are accounted for, but only a knowledge of the sample mean and standard deviation is required, and (c) the approximations (especially on a weight basis) lead to values within the limits of error in dissolution studies, thus posing the question of whether published exact experessions have practical value.

Chemistry, Pharmaceutical↗

PubMed1977

Dissolution profiles for multisized prednisolone acetate suspensions.

Particle-size measurements and in vitro dissolution characteristics of commercial and formulated suspensions of prednisolone acetate were determined using a resistance particle counter and a spinning filter apparatus, respectively. Significant differences in dissolution rates were noted for the commercial suspensions. Particle size affected dissolution but did not account for all observed variations in the dissolution rate. Formulation differences, specifically the presence of hydroxypropyl methylcellulose, in suspensions seemed to be important in dissolution.

Chemistry, Pharmaceutical↗

PubMed1976

Solubility of straight-chain and branched alkyl barbiturates in straight-chain alcohols.

The solubilities of a series of chemically related barbiturates, including some medically useful ones as well as phenobarbital, were determined at 25 degrees in the straight-chain alcohols methanol through butanol. The solubility values are given in both milligrams per milliliter and the mole fraction notation. The solubility in methanol was the highest and decreased nonlinearly for the solubility in 1-butanol. In several cases, mole fraction solubility gave shouldering or peaking as a function of the carbon number of the solvent. This series of barbiturates was broken down into two subsets of straight-chain and branched alkyl barbiturates, and solubility ratios in these subsets were considered.

Alcohols↗