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S H Yalkowsky

Publications and source records attributed to S H Yalkowsky.

At least 55 records · Page 3Linked to original sources
PubMed1997

A method for the rapid estimation of sublimation rates of organic compounds at standard temperature and pressure.

A method for the rapid estimation of the sublimation rates of organic compounds at standard temperature and pressure (STP; 298 K and 101.3 kPa, respectively) is presented. Thermogravimetric analysis was used to obtain accelerated sublimation rates for anthracene at a series of elevated temperatures and reduced pressures. An empirical equation relating these parameters was used to extrapolate to the STP sublimation rate. This value is in good agreement with the measured value.

Pressure↗
PubMed1997

Lysis of human red blood cells. 4. Comparison of in vitro and in vivo hemolysis data.

The dynamic in vitro method developed by the authors and other available in vitro methods were used to determine the degree of hemolysis induced by several cosolvent vehicles that have previously been evaluated in vivo. The in vitro data generated for each of these vehicles was compared with the in vivo hemolysis data to assess the ability of the method to estimate in vivo hemolysis. The results show that the in vitro data generated by the dynamic method are in agreement with the in vivo data for each vehicle. Therefore, the potential for formulations to induce intravascular hemolysis after injection can be determined by this dynamic in vitro method. With this information, hemolytically safe formulations can more easily be prepared.

Hemolysis↗
PubMed1997

Systemic delivery of insulin via an enhancer-free ocular device.

Sodium insulin and zinc insulin ocular devices are developed for the systemic delivery of insulin. The devices consist of Gelfoam (absorbable gelatin sponge, USP) as an insulin carrier and do not contain any surfactant or absorption enhancer. Sodium insulin was dissolved in either distilled water, 30% ethanol, or 10% acetic acid for either eyedrop or device preparations. Because of its low solubility in water and aqueous ethanol solution, zinc insulin was dissolved in 10% acetic acid-water solution for eye devices preparation. Commercially available Humulin R was selected as another source of zinc insulin and was used as an eyedrop as well as one device preparation. Only 10% acetic acid solution-treated insulin devices produce significant blood glucose reduction. The dose of insulin used in this study is < 50% of that used in the reported insulin devices.

Animals↗
PubMed1995

Effect of pH on injection phlebitis.

Formulation pH has been reported to be responsible for the incidence of phlebitis. In this study, the effect of pH on injection phlebitis is investigated. Buffers of varying pHs were examined for their ability to produce phlebitis in rabbits. Thermal measurements as well as visual evaluations were used for phlebitis quantitation. The results show that formulation pH between 3.0 and 11.0 does not contribute to the incidence of phlebitis when administered as an iv bolus injection.

Animals↗
PubMed1995

Self-association of dexverapamil in aqueous solution.

The pKa and intrinsic solubility of monomeric dexverapamil were determined from its pH-solubility profile to be 8.90 and 6.6 x 10(-5) M, respectively. The solubility of dexverapamil below pH 7.0 was higher than expected on the basis of the aforementioned values. This unusually high solubility is believed to be due to the self-association of cationic dexverapamil. The apparent pKa of the self-associated drug is estimated to be approximately 7.99. The self-association of dexverapamil hydrochloride is supported by the fact that it is surface active and that it increases the solubility of both naphthalene and anthracene in aqueous solutions. The dependence of the drug solubility on pH and the solubilization of naphthalene and anthracene as a function of ionized drug concentration suggest that the self-associated dexverapamil is a cationic dimer.

Anthracenes↗
PubMed1995

Studies in phlebitis. VII: In vitro and in vivo evaluation of pH-solubilized levemopamil.

We describe a computational model and an in vitro experiment for assessing whether or not a pH-solubilized drug has the potential to precipitate upon dilution with blood. The computational model enables an efficient means of selecting buffer concentration and pH, and the in vitro test provides a simple experimental validation. Both means of screening are applied to the formulation of the weakly basic drug levemopamil-HCI. A buffered formulation of levemopamil is chosen from the computational model and shown to be free of precipitation upon dilution in vitro and to not produce phlebitis in the rabbit ear model. In comparison, an unbuffered formulation at the same pH and drug concentration precipitates in vitro and causes significant phlebitis in vivo. The results of this study reinforce the importance of buffering parenteral formulations instead of simply adjusting the pH of the formulation.

Animals↗
PubMed1994

Solubility of organic solutes in ethanol/water mixtures.

The log-linear solubilization model was applied to the experimental solubility data of 109 organic compounds in ethanol/water mixtures. It is found that the extent of solubilization strongly depends on the solute hydrophobicity and the ethanol concentration in the solvent mixture. Patterns of deviation from the log-linear model are related to the structure and hydrophobicity of the solutes. Predictive equations were obtained by regression of the experimental data with solute octanol/water partition coefficient (log Kow). The logarithms of the solubilization and the solute log Kow range over 11 orders of magnitude. The solubilities of chrysene, perylene, benzo[a]pyrene, pentachlorobenzene, and hexachlorobenzene in ethanol/water mixtures were experimentally determined, and the results fit well into the model.

Chemical Phenomena↗
PubMed1993

Controlled delivery of pilocarpine. 1. In vitro characterization of Gelfoam matrices.

The potential of Gelfoam absorbable gelatin sponge as a carrier for ophthalmic delivery of pilocarpine was examined. Prolonged in vitro release of pilocarpine was achieved through pharmaceutical modification of the device by embedding a retardant in the pores. The device embedded with cetyl ester wax released pilocarpine in a zero-order pattern (release exponent = 0.93 +/- 0.04) for up to 5 hr. This result corresponded well with a linear penetrant uptake by this device. The device impregnated with polyethylene glycol 400 monostearate exhibited anomalous drug transport with a release exponent of 0.63 +/- 0.02. The absorption of water by this retardant and the formation of a gel layer on the surface slowed the penetration of the release medium into the deeper sections of the matrix, as well as the rapid outward diffusion of drug, resulting in a prolonged release of pilocarpine.

Chromatography, High Pressure Liquid↗
PubMed1992

Acceleration of heat transfer in vial freeze-drying of pharmaceuticals. II. A fluid cushion device.

A simple device for the improvement of freeze-drying efficiency is described. The device is an aluminum foil bag which contains a small amount of glycerin. The device can be either reusable or disposable. When placed on a freeze-drying tray the liquid is about 1 mm thick. When vials are placed on the device it conforms to the shape of the vial bottoms. Since both the aluminum foil and the glycerin are better heat conductors than a vacuum, the device improves heat transfer from the shelf to the vial. Drying times obtained with and without the device are compared for different sizes as well as different types of vials. In most cases the use of the device reduces the drying time by nearly a factor of two. The use of the device also increases vial-to-vial uniformity and minimizes the effect of spillage.

Freeze Drying↗
PubMed1991

Studies in phlebitis: detection and quantitation using a thermographic camera.

A new method for the detection of acute phlebitis in superficial veins is investigated. A thermographic camera is utilized for the quantitation of temperature changes in a rabbit ear model. A control group receiving no injection is compared against each of five treatment groups receiving these commercially available parenterals: amiodarone hydrochloride, phenytoin sodium, mechlorethamine hydrochloride, cephalothin sodium, and diazepam. The vehicles of the above-mentioned drugs as well as several commonly used organic cosolvents are also investigated. Local tissue responses to the parenteral challenges are measured and a good correlation between the visual and the thermographic data was seen.

Animals↗