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Biomedical subjects

Z T Chowhan

Publications and source records attributed to Z T Chowhan.

29 records · Page 2Linked to original sources
PubMed1978

pH-solubility profiles or organic carboxylic acids and their salts.

The solubilities of naproxen, 7-methylsulfinyl-2-xanthonecarboxylic acid, 7-methylthio-2-xanthonecarboxylic acid, and their sodium, potassium, calcium, and magnesium salts were determined as a function of pH. The results on the solubility of naproxen and its salts were in excellent agreement with the theoretical profiles describing the relationship between pH values of the solutions and the dissociation constant of the acid. The solubilities of the two xanthonecarboxylic acids were higher at higher pH values than the values calculated when complete dissociation in solution was assumed. The influence of the salt species on the solubility of organic carboxylic acids, at and above pH values of complete ionization, cannot be predicted even qualitatively from equations used for alkali and alkaline earth metal salts.

Calcium↗
PubMed1978

Effect of surfactants on percutaneous absorption of naproxen I: comparisons of rabbit, rat, and human excised skin.

The in vitro skin penetration model using excised skin from rats, rabbits, and humans was examined to evaluate the relative effect of surfactants on percutaneous absorption of naproxen. Differences in the magnitude of the effect of surfactants in promoting percutaneous absorption of naproxen through skins of different species were observed. For comparative evaluations of the formulation effects on percutaneous absorption, such as the effect of surfactants, in vitro studies with animal skin may not provide information in agreement with in vitro human skin.

Animals↗
PubMed1978

Hardness increase induced by partial moisture loss in compressed tablets and its effect on in vitro dissolution.

The hardness increase induced by partial moisture loss in compressed tablets was studied. Several factors such as the type and percentage of the excipient, the water solubility and hygroscopicity of the excipient or drug, and the influence of frequently used binders were investigated. The results indicate that the tablets increased in hardness by the recrystallization of the soluble excipient or the soluble drug in the void spaces This recrystallization occurred because of the moisture loss after expulsion of the solution of the excipient or drug in the void spaces on compression. The large increase in hardness induced by the partial moisture loss did not decrease in vitro dissolution appreciably. This result was clearly different from the hardness increase caused by higher compression loads in the absence of a moisture-induced effect, which showed a decrease in the in vitro dissolution as the hardness was increased.

Crystallization↗
PubMed1978

Effect of surfactants on percutaneous absorption of naproxen II: in vivo and in vitro correlations in rats.

The effect of surfactants on percutaneous absorption of naproxen was studied using rat in vivo models. The in vivo normalized relative absorption rates were in good agreement with the in vitro relative flux. An antipyretic model in the rat could not show relatively small increases in percutaneous absorption caused by the surfactants. Based on these results, it is apparent that reliance on the rat, using either in vitro or in vivo models, may lead to erroneous conclusions when considering the effect of surfactants on human percutaneous absorption of drugs such as naproxen.

Animals↗
PubMed1978

The use of mixtures of topical corticosteroids as a mechanism for improving total drug bioavailability: a preliminary report.

The feasibility of using mixtures of corticosteroids as a mechanism for enhancing total percutaneous absorption of drug has been investigated. The results of this study indicate that under certain conditions, mixtures of corticosteroids exhibit independent solubility, partitioning and diffusion behavior. Mixtures of three 21-esters of fluocinolone acetonide were found to penetrate excised human skin independently. The mixture flux rate was demonstrated to greatly exceed that attained with any of the component steroid esters at an equal concentration. A mixture composition containing a total steroid concentration of 0.015% was shown to produce significantly greater in vivo human vasoconstriction than any of the individual steroids at comparable concentrations. These results strongly support the potential clinical utility of certain topical corticosteroid mixture compositions.

Administration, Topical↗
PubMed1977

Everted rat intestinal sacs as an in vitro model for assessing absorptivity of new drugs.

An in vitro model that utilizes everted rat intestinal sacs was evaluated for assessing the absorptivity of several analogs of potential drug substances prior to formulation work and clinical trials. This model not only is a useful qualitative tool for assessing absorptivity of structurally related compounds but also yields some insight into the process involved in drug absorption. Notwithstanding the complexities involved in the absorption processes, the data support the hypothesis that the absorption of organic electrolytes mainly takes place by the partitioning of the unionized species into the lipoidal membranes and then diffusion.

Animals↗
PubMed1976

Pulmonary absorption studies utilizing in situ rat lung model: designing dosage regimen for bronchial delivery of new drug entities.

The absorption of 7-methylsulfinylxanthone-2-carboxylic acid, 7-(methylthio)xanthone-2-carboxylic acid, and their sodium salts from the respiratory tract of anesthetized rats was studied after intratracheal administration of 0.1 ml of a solution or suspension containing the drug. At various times after administration, the lungs and trachea were removed and assayed radiochemically for unabsorbed drug. Sodium 7-(methylthio)xanthone-2-carboxylate from solution was absorbed approximately 20 times faster than sodium 7-methylsulfinylxanthone-2-carboxylate from a solution. The absorption from solutions was three to four times faster than the absorption from suspensions. For inhalation aerosol dosage forms intended for prophylactic use, the drug entity with slower systemic absorption probably would be more desirable than the drug entity with rapid absorption. Rapid systemic absorption following inhalation of powder or liquid aerosols would lead to more frequent dosing if the biological activity is related to the drug concentration in the tracheobronchial tissues. Therefore, the powder or liquid inhalation aerosols of organic acids rather than the corresponding sodium salts may be preferable for designing a dosage regimen. However, if the dosage form is intended for utilizing the bronchodilator activity of the compound, the drug entity with rapid absorption is more desirable. Therefore, in the treatment of asthmatic attacks, liquid or powder inhalation aerosols of the sodium salt of the rapidly absorbing drug entity are preferable. The absorption rates were directly proportional to concentration when the initial concentration of sodium 7-methylsulfinylxanthone-2-carboxylate was varied over a 333-fold range. The effect of the pH of the drug solution administered intratracheally to the rat lung indicated a sharp increase in the pulmonary absorption at a pH near the pKa. The results suggested that structurally related xanthones are absorbed possibly by passive diffusion across the lipoidal region of the pulmonary membranes and that the absorption of organic acids and organic electrolytes is mainly controlled by the lipid solubility of the unionized species.

Absorption↗
PubMed1975

Release of corticoids from oleaginous ointment bases containing drug in suspension.

Simplified methods for studying the release of drugs suspended in oleaginous ointment bases were developed. These procedures were used in studying the release rates of two corticoids, fluocinonide and flucloronide, from white petrolatum and petrolatum containing various adjuvants. A practical method for measuring drug solubilities was developed and used in determining solubilities of these corticoids in ointment bases. When using physical data obtained from model ointments, the release rates of drugs from modified ointment bases were predicted. Comparisons of the observed and predicted rates from ointments containing hydrophobic adjuvants indicated the usefulness of the physical model approach in predicting the release rates. For ointments containing emulsifying agents, the simple model used did not provide useful predictions.

Adrenal Cortex Hormones↗