Biomedical subjects

S H Yalkowsky

Publications and source records attributed to S H Yalkowsky.

At least 91 records · Page 5Linked to original sources

PubMed1980

Solubility and partitioning I: Solubility of nonelectrolytes in water.

On the basis of a semiempirical analysis, an equation was obtained that enables the estimation of the aqueous solubility of either liquid or crystalline organic nonelectrolytes: (see formula in text) where log PC and delta Sf are estimated from the chemical structure and MP is either known or experimentally determined. Analysis of this equation provides a means of assessing the role of crystal structure [as reflected by the melting point (MP) and the entropy of fusion (delta Sf)] and of the activity coefficient [as reflected by the octanol-water partition coefficient (PC)] in controlling the aqueous solubility of a drug. Techniques are also provided for estimating the entropy of fusion of organic compounds.

Alcohols↗

PubMed1979

Stability of E-type prostaglandins in triacetin.

A drug delivery system for E-type prostaglandins is described. In this system, consisting of drug dissolved in triacetin and filled into soft gelatin capsules, normally unstable prostaglandins show excellent stability at room temperature.

Drug Stability↗

PubMed1979

Fusion of disubstituted benzenes.

The entropy of fusion of 84 disubstituted benzenes was essentially constant and independent of the participation of the compounds in intramolecular or intermolecular hydrogen bonding. It was also independent of the shapes, sizes, and dipole moments of the rigid molecules studied. While the entropy of fusion was independent of these parameters, the melting point and the heat of fusion showed a direct dependence on molecular properties.

Benzene Derivatives↗

PubMed1977

Convective diffusional analysis for drug transport through a tubular polymeric membrane.

The transport of three p-aminobenzoate esters (ethyl, butyl, and hexyl) through a tubular dimethyl polysiloxane membrane into a flowing liquid was investigated. The tubular configuration permits the exact determination of the convective diffusional contribution to membrane transport with models that account for fluid hydrodynamics. The observed transport behavior ranged from complete convective diffusion control for the hexyl ester to complete membrane control for the ethyl ester; the butyl ester exhibited a change in control with flow rate. The implications of convective diffusional considerations to intestinal absorption and dissolution studies are discussed.

4-Aminobenzoic Acid↗

PubMed1976

Solubility of nonelectrolytes in polar solvents IV: nonpolar drugs in mixed solvents.

The molecular and group surface area approach to solubility is shown to be applicable to mixed aqueous solvent systems. An equation is derived which is consistent with the exponential increase in the aqueous solubility of nonpolar drugs that frequently accompanies the addition of a cosolvent. This equation predicts that: (a) the ability of a drug to be solubilized by a cosolvent is proportional to its hydrophobic surface area per molecule, and (b) the ability of a cosolvent to solubilize any drug is inversely proportional to its interfacial tension against a reference liquid hydrocarbon. These predictions are experimentally verified with solubility studies of several alkyl p-aminobenzoates in propylene glycol-water mixtures and of hexyl p-aminobenzoate in mixtures of water the ethanol, methanol, ethylene glycol, propylene glycol, glycerin, and formamide.

Aminobenzoates↗

PubMed1976

Partition coefficients and surface areas of some alkylbenzenes.

The experimentally measured log P values (logarithms of partition coefficients) of a number of alkylbenzenes are shown to be quantitatively related to the hydrocarbon surface area HSA of the molecule by pi = 0.0275 X HSA - 0.863 (correlation coefficient =0.996, standard deviation = 0.071). The use of surface area as a correlating parameter eliminates the need for correction factors to account for branching, cyclization, ring fusion, and "backfolding". Futhermore, surface area calculations provide a conceptual basis for understanding how conformation can effect partitioning.

Benzene Derivatives↗

PubMed1975

Solubility of nonelectrolytes in polar solvents III: Alkyl p-aminobenzoates in polar and mixed solvents.

The relative solubilities of n-alkyl p-aminobenzoates in water, proplyene blycol-water mixtures, proplyene glycol, and several other pharmaceutically important solvents can be predicted on the basis of a theoretical equation. This equation relates the activity coefficient of the hydrophobic portion of the molecule to the product of its surface area and its interfacial tension [free energy per unit area of a hydrocarbon (tetradecane) against the polar or semipolar solvent of interest]. The assumptions, conclusions, and applicability of the theorectical relationship are compared to those of the Scatchard-Hildebrand approach.

Alcohols↗

PubMed1975