Matthew A. Augustine

Common ion effect on solubility and dissolution rate of the sodium salt of an organic acid

The solubility and the dissolution rate of the sodium salt of an acidic drug (REV 3164; 7‐chloro‐5‐propyl‐1H,4H‐[1,2,4]triazolo[4,3‐a]quinoxaline‐1,4‐dione) decreased by the effect of common ion present in aqueous media. The solubility of the sodium salt of REV 3164 in a buffered medium was much lower than that in an unbuffered medium. Also, the presence of NaCl decreased its solubility in water. The apparent solubility product (Ksp ***of the salt, however, did not remain constant when the concentration of NaCl was changed. A decrease in Ksp value with the increase in NaCl concentration was observed; for example, the Ksp values at 0 and 1 M NaCl were 7ṁ84 times 10−4 and 3ṁ94 times 10−4 M2, respectively. Even when corrected for the effect of ionic strength, the solubility product decreased. This decrease in the solubility product in the presence of NaCl indicated a decrease in the degree of self‐association (increase in activity coefficient) of the drug in aqueous media.

Hygroscopicity of Celiprolol Hydrochloride Polymorphs

AbstractThe moisture absorption of two crystalline forms (form I and form II) of celiprolol hydrochloride was investigated at different relative humidities. Celiprolol hydrochloride form I was found to be less hygroscopic than celiprolol hydrochloride form II. It was also found that the high melting form I undergoes a transition to a low melting form II at high relative humidity.

Studies on the Light Stability of Flordipine Tablets in Amber Blister Packaging Material

AbstractAccelerated light conditions have been used in the evaluation of light stability of flordipine tablets. The tablets were subjected to exaggerated light exposure in a fadeometer and to 150 foot candles of fluorescent light in a light cabinet. A comparative study was conducted between tile tablets exposed directly to light and to those covered with amber vinyl sheeting. The color change was evaluated by a tristimulus colorimeter using the Hunter L, a, b scale. The b coordinate was selected for the final evaluation of light stability since it corresponded closely to the visual increase in yellowness with time. The data demonstrated that the amber colored vinyl sheeting had an excellent protective effect on the discoloration of flordipine tablets. Data obtained in the fadeometer in six hours as well as results from exposure in the light cabinet for twenty-nine days, facilitate the comparative evaluation of light stability of flordipine tablets. One hours exposure to fade oneter was found to be equal ...

EFFECT OF PARTICLE SIZE ON THE DISSOLUTION CHARACTERISTICS OF CHLORTHALIDONE

AbstractThe particle size reduction of chlorthalidone by fluid energy milling, Alpine milling and Fitzpatrick milling were evaluated. The desired particle size was achieved by both the fluid energy milling and Alpine milling processes. Alpine mil1ing, however, is a more complex process and is susceptible to product decomposition, whereas fluid energy milling is a simple and efficient process without any risk of product decomposition. The desired particle size cannot be achieved by Fitzmilling because of the low probability of impaction force on particles. The dissolution rate of the chlorthalidone from chlorthalidone/propranolol hydrochloride tablets (25/80 mg) prepared with fluid energy milled chlorthalidone was significantly better than the tablets prepared with Fitzpatrick - milled chlorthalidone. The minimum effective specific surface area of chlorthalidone needed for maximum dissolution in water was found to be around 3.5 m2/g.