Journal of Thermal Analysis and Calorimetry, Vol. 59 (2000) 657–661 APPLICATION OF THERMAL ANALYSIS IN THE CHARACTERIZATION OF ANTI-HYPERTENSIVE DRUGS R. O. Macêdo * , T. Gomes do Nascimento, C. F. Soares Aragão and A. P. Barreto Gomes Pharmaceutical Technology Laboratory of the Federal University of Paraíba, Campus 1, João Pessoa, Paraíba, 59059-900 Brazil Abstract The present work reports studies of the thermal behaviour of some anti-hypertensive drugs. Their purities were determined by DSC and specialized pharmacopeial methods. The thermo- gravimetric data allowed determination of the kinetic parameters: activation energy, frequency factor and reaction order. The activation energy values suggest the following sequence of sta- bility: nifedipine>propanolol hydrochloride>captopril. Analysis of the DSC data indicated that the degrees of purity of nifedipine, captopril and propanolol hydrochloride were similar to those found by pharmacopeial methods BP 93 and USP 23. The simplicity, speed and low oper- ational costs of thermal analysis justify its application in the quality control of pharmaceutical drugs. Keywords: anti-hypertensive drugs, quality control, thermal analysis Introduction Thermogravimetry is an analytical, quantitative and comparative method, capable of producing fast and reproducible results. It can be used in the quality control of drugs, with a view to improvement of the final product and for the determination of drug quality via the technological parameters [1]. Differential scanning calorimetry (DSC) can be used in the pharmaceutical industry as an analytical tool of great importance for the identification and purity testing of active drugs, yielding results rapidly and efficiently. DSC has been ap- plied for the quality control of raw materials used in pharmaceutical products [2]. The present work reports studies of the thermal behaviour of some anti- hypertensive drugs, in comparison with the methods employed for identification and purity testing in the pharmaceutical industry [3–5] in relation to the applica- tion of thermal techniques in the quality control of medications. 1418–2874/2000/ $ 5.00 © 2000 Akadémiai Kiadó, Budapest Akadémiai Kiadó, Budapest Kluwer Academic Publishers, Dordrecht * Author for correspondence: e-mail: ruimaced@funape.ufpb.br; fax: 55-83-216-7371