No abstract

Four crystal modifications of acyclovir were isolated by recrystallization and characterized by powder X-ray diffractometry, differential scanning calorimetry, and thermogravimetric analysis. It was confirmed that Form 3 is a hydrate and Form 4 is an acetic acid solvate. The dissolution patterns of three crystal forms of acyclovir were studied in water at 37 +/- 0.5 degrees C, 90 rpm for 120 minutes. The amount dissolved at 120 minutes was highest for Form 1, followed by Form 2 and Form 3. After storage of 25 hours at 0% RH (silica gel, 20 degrees C) Form 3 was transformed to Form 2.

No abstract

The objective of this work was to investigate the existence of polymorphs and pseudopolymorphs of naproxen and the transformation of crystal forms. Four crystal forms of naproxen have been isolated by recrystallization and characterized by differential scanning calorimetry, powder X-ray diffractometry and thermogravimetric analysis. The differential scanning calorimetry and powder X-ray diffractometry patterns of the four crystal forms were different respectively. In the dissolution studies in pH 6.8 ± 0.05 buffer equilibrated at 37 ± 0.5°C, the solubility of four crystal forms was similar (within the error range). After storage of 1 month at 0% RH (silica gel, 20°C), 52% RH (saturated solution of Na(2)Cr(2)O(7.2)H(2)O/20°C) and 95% RH (saturated solution of Na(2)HPO(4)/20°C), Form 2 and Form 4 were transformed to Form 1, but Form 3 and Form 1 were not transformed and they were shown to have a good physical stability at room temperature for 1 month.

Ferulic acid (3-methoxy, 4-hydroxy cinnamic acid) is a flavoid component possessing antioxidant property. The compound is currently under development as a new drug candidate for the treatment of the dementia. The objective of this preformulation study was to determine the physicochemical properties of ferulic acid. The n-octanol to water partition coefficients of ferulic acid were 0.375 and 0.489 at the pHs of 3 and 10, respectively. Accelerated stability study for ferulic acid indicated that the t 90 value for the drug was estimated to be 459 days at 25 degrees C. Ferulic acid was also found to be unstable under the relative humidity of more than 76%, probably because of the hygroscopic nature of the drug. In order to study compatibility of ferulic acid with typical excipients, potential change in differential scanning calorimetry spectrum was studied in 1:1 binary mixtures of ferulic acid and typical pharmaceutical excipients (e.g., Aerosil, Avicel, CMC, Eudragit, lactose, PEG, PVP, starch and talc). Avicel, CMC, PVP and starch were found to be incompatible with ferulic acid, indicating the addition of these excipients may complicate the manufacturing of the formulation for the drug. Particle size distribution of ferulic acid powder was in the size range of 10-190 microm with the mean particle size of 61 microm. The flowability of ferulic acid was apparently inadequate, indicating the granulation may be necessary for the processing of the drug to solid dosage forms. Two polymorphic forms were obtained by recrystallization from various solvents used in formulation. New polymorphic form of ferulic acid, Form II, was obtained by recrystallization from 1,4-dioxane. The equilibrium solubility for Form I was approximately twice of that for Form II. The dissolution rate of Form II was higher than that of Form I in the early phase (<6 min). Therefore, these physicochemical information has to be taken in the consideration for the formulation of ferulic acid.