Issue Date: July 27, 2009
Bulky acetaminophen pills can be a headache to swallow. That's because crystals of the analgesic don't easily compress into a stable tablet without the addition of binding agents that increase the pill's girth. A new proof-of-principle study suggests one possible weight-loss program for the hefty tablets is to crystallize the active ingredient with companion molecules, thus producing a more compressible crystal.
In particular, William Jones, a chemist at Cambridge University, and his colleagues tried cocrystallizing acetaminophen with various small molecules that FDA generally recognizes as safe, including malonic acid, phenazine, oxalic acid, and theophylline, and showed that the latter two improved the mechanical properties of the resulting crystal (Adv. Mater., DOI: 10.1002/adma.200900533). Although cocrystals are known to improve the stability, solubility, and dissolution rate of several active ingredients, the only precedent for improving mechanical properties of an active ingredient using cocrystallization is a recent study on caffeine (Cryst. Growth Des. 2008, 8, 1575).
This new work is "elegant," says Naír Rodríguez-Hornedo, a pharmaceutical scientist at the University of Michigan. But she points out that solving one delivery problem—such as reducing pill size by modulating the active ingredient's mechanical properties with cocrystallization—may come at a cost for other important properties such as bioavailability and solubility. Also, any bioactivity of the cocrystallization molecule would have to be complementary to the active ingredient's. However, the proof-of-principle work "gets us closer to understanding material behavior, and more important, to designing materials with desired properties," she says.
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