Counterfeit and substandard drugs, usually illegally marketed and most probably illegally manufactured have become a noticeable problem in most countries recently. As it might be expected, the spectrum of fake pharmaceuticals ranged from antimicrobial, antihistaminic, hormone through anti-sexual dysfunction remedies. The scope of illegally marketed drugs is different in poor, developing countries and these in North America and Europe. Still in many countries the health care authorities are not fully aware of the problem and health risk for the population, however several initiatives to change this situation have been taken lately. The lack of specific regulations concerning internet marketing and the lack of systematic control of the pharmaceutical market, both legal and illegal, increases the risk. In such case the need of fast, easy, reliable and not expensive methods of drugs screening is essential. No wander that the NIR (near infrared) spectroscopy became popular in this respect.

Our results obtained for counterfeit samples of Viagra^® and Traditional Chinese Herbal Medicines show that the X-ray powder diffraction, especially when using new, fast diffraction techniques, including multilayer mirrors and position-sensitive counters, is a method suitable for pharmaceutical market screening control for counterfeit and substandard drugs. This method can easily discriminate fake and original samples, even by visual examination of diffraction patterns, what can be done also by not highly experienced employees. All statistical methods for principal components analysis etc., usually utilized for spectroscopic data evaluation e.g. NIRS, can be also employed, however are not necessary. Well-resolved picks and their characteristic 2θ values can be used for examining powder diffraction databases in qualitative composition analysis. Diffraction patterns can serve as fingerprints of manufacturers – both legal and illegal – since even small changes in composition are visible. It is worth noting, however, that X-ray powder diffraction, same as NIR spectroscopy, is not a method of trace analysis, and that for those purposes other methods are more sensitive and hence more reliable. The power of XRPD in medicines control demonstrates its unusual application for identification of rubber closures fragments.

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1. Determination of sibutramine and desmethylsibutramine in Chinese Herbal Medicines by HPLC-ED, HPLC-MS/MS end XPRD methods