IDENTIFICATION OF DRUGS IN PHARMACEUTICAL DOSAGE FORMS BY X-RAY-POWDER DIFFRACTOMETRY

A simple X-ray powder diffractometric (XRD) method was developed for t he identification of the active ingredient in a variety of dosage form s. The method was successfully used to unambiguously identify the acti ve ingredient(s) in tablet, capsule, suppository and ointment formulat ions. The unique feature of the method is that it provides information about the solid-stale of the drug. Thus, a capsule formulation contai ning anhydrous ampicillin was readily distinguished from that containi ng ampicillin trihydrate. The USP stipulates the use of the beta-polym orphic form of anhydrous carbamazepine in carbamazepine tablets. Conta mination by the cc-polymorph (down to a level of 1.4% w/w of the formu lation) could be detected. In some of the multicomponent formulations, there was a pronounced overlap of the powder patterns of ingredients which made identification difficult. This problem was solved by using a pattern subtraction technique, which permitted selective subtraction of the XRD pattern of the constituents of the formulation from the ov erall XRD pattern. Such an approach enabled identification of the drug even when it constituted only 5%, w/w of the formulation. The method also permitted simultaneous identification of the multiple active ingr edients in trimethoprim-sulfamethoxazole and acetaminophen-aspirin-caf feine formulations. (C) 1997 Elsevier Science B.V.