In Search of an Optimal Solid Form - Pharmaceutical Technology

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PharmTech Europe

In Search of an Optimal Solid Form
The solid form of an API plays a crucial role in drug quality, and advancing methods for screening, detection, and characterization is key.

Pharmaceutical Technology
Volume 35, Issue 7, pp. 44-48

Other approaches

Researchers at the University of Missouri recently reported on a new method for converting drugs from one crystalline form to another by applying gas-induced transformations of the antibiotic clarithromycin and lansoprazole, the API in the gastrointestinal drug Prevacid.

For clarithromycin, the researchers converted the kinetic solvent and guest-free crystal forms to the commercially thermodynamically stable polymorph with a reduction in energy costs relative to other commonly used methods. Typical methods involve desolvation of the initial form to a second form, which is heated for 18 h at 110 C to finally produce the desired polymorph. In the gas-induced process, the clarithromycin crystals were pressurized with carbon dioxide at 350 psi for direct conversion of the initial form to the final thermodynamically stable form in 4 h. For lansoprazole, the researchers also used carbon dioxide to convert the ethanol hydrate of lansoprazole to the solvent-free form that is used commercially. This process improved the approach used in synthesizing lansoprazole, which involves a solvate that readily decomposes and is stirred in water, filtered, and dried intensively (8, 9).

Patricia Van Arnum is a senior editor at Pharmaceutical Technology, 485 Route One South, Bldg F, First Floor, Iselin, NJ 08830 tel. 732.346.3072,


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2. T.N. Pham et al., Mol. Pharm. 7 (5), 1667–1691 (2010).

3. NMR Crysallography, R. Harris, R.E. Wasylisher, and M.J. Duer, Eds. (John Wiley & Sons, Chichester, UK, 2009).

4. S.M. Reutzell-Edens, "NMR Crystallography and the Elucidation of Structure–Property Relationships in Crystalline Solids," in Engineering of Crystalline Materials Properties, NATO Science for Peace and Security Series B: Physics and Biophysics, J. Novoa, D. Braga, and L. Addadi Eds (Springer, Dordrecht, The Netherlands, 2008), pp. 351–374.

5. J.S. Stevens, S.J. Byard, and S.L.M. Schroeder, J. Pharm. Sci. 99 (11), 4453–4457 (2010).

6. J. S. Stevens et al., J. Phys. Chem. B. 114 (44) 13961–13969 (2010).

7. J.S. Stevens et al., J. Pharm. Sci. 100 (3) 942– 948 (2011).

8. J. Tian, S.J. Dalgarno, and J.L. Atwood, J. Am. Chem. Soc. 133 (5), 1399–1404 (2011).

9. C. Arnaud, Chem. & Eng News 89 (3), 8 (2011).


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