Crystal habits and dissolution behavior of Aspirin.

The Confusion of Indexing Aspirin Crystals

“…The mistake probably stems from the inconsistent indexing caused by the use of a nonstandard space group setting. The face indexing of aspirin crystal is not incorrect, 8,9 because their assignment is relative to their choice of P2 1 /a. However, if these face indices are used to examine surface moieties based on a P2 1 /c description without the necessary index transformation, the (100) face will be mistaken as (001), and vice versa.…”

“…The confusion in the literature seems to stem from the original assignment of the space group and indices of the crystal faces. [7][8][9]17 This communication presents experimental evidence to clarify the difference between the two major faces of aspirin crystal, and to revise our conclusion of the contact angle data for further interpretation of surface wettability.…”

“…6,7 Using the parameters from this report the predominant face was identified as (001). 8,9 However, the first full structure determination by single crystal XRD was not until 1964. 10 This report and others that followed assigned a different setting of the same space group, that is, P2 1 /c.…”

Potential polymorphs of aspirin

“…10 ᎐ 12 Unfortunately, no x-ray diffraction data were given by the investigators for the new forms. Two phenomena constitute possible sources of the differences noted between various batches of aspirin: the influence of different solvents on crystal habit, 13 and differing rates of Ž . 14 degradation in particular, hydrolysis .…”

Bioavailability and Bioequivalence Study in Correlation of Biopharmaceutics Classification System (Bcs) and Possible Modification

“…The different crystal form of a drug has different physicochemical characteristics, namely crystal shape, crystal size, melting point, density, flow properties solubility pattern, dissolution characteristics and XRD pattern, though they are chemically identical. A physical form having an improved dissolution rate and solubility is useful for improving the bioavailability of a drug 48,49 . The crystal habit is an important variable in pharmaceutical manufacturing, where some factors, such as the polarity of crystallization solvent and the presence of impurities in the solvent, affect crystallization [50][51][52] .…”