DSC and spectroscopic studies of disulfiram radiostability in the solid state Barbara Marciniec • Katarzyna Dettlaff • Marek Naskrent • Zuzanna Pietralik • Maciej Kozak Received: 30 December 2010 / Accepted: 18 July 2011 / Published online: 11 August 2011 Ó The Author(s) 2011. This article is published with open access at Springerlink.com Abstract The effect of ionising radiation on the physico- chemical properties of disulfiram (Antabuse, Esperal, bis- diethylthiocarbamoil disulphide) has been studied by DSC, FTIR, EPR, MS, TLC and HPLC. Sterilisation was carried out in the solid state, at room temperature and normal air humidity using the electron beam of 9.96 Mev from accel- erator. All the measurements were made simultaneously for the irradiated and nonirradiated substance. It has been found that the drug studied in solid phase when subjected to an electron beam corresponding to the irradiation in the doses 10–100 kGy shows the presence of free radicals (EPR), and a change in colour from white to pale green-grey that dis- appears after solution in water or methanol. After the irra- diation with the dose of 100 kGy, its melting point and enthalpy slightly decreased. Also the content of the active substance decreases (HPLC -1.5%, UV -3.6%, iodometric titration method -2.7%) and trace amounts of the radiolysis products appear (HPLC). The substance irradiated with the doses 10–50 kGy does not show changes in the melting point, in the content and presence of the radiolysis products. The EPR results have shown that free radicals disappear after about a year and the discolouring disappears with them. The results of this study have shown that disulfiram can be subjected to sterilisation by irradiation with no deterioration of its physico-chemical properties, but a long time of storage needed to remove free radicals and discolouration questions the economic justification for this type of sterilisation. Keywords Disulfiram Á Radiosterilization Á Stability Introduction Starting from the 1980s, increasing interest has developed in radiation sterilisation [1–5]. Beta (using electron beam) or gamma irradiation is an alternative and very attractive method for sterilization of pharmaceutical substances or medical devices [6, 7]. The main difference between electron-beam and gamma-radiation is the dose. The same irradiation dose using gamma radiation can be obtained in several hours, whereas electron beam radiation requires only a second [8]. The sterilisation procedures using irra- diation have many advantages, such as high efficiency, no temperature requirements, possibility of sterilisation in packages but on the other hand, the ionisation radiation applied can damage a given drug being sterilised [9] so the effect of sterilisation radiation should be checked before its application. One of the most widely used methods of analysing the drugs purity and possible changes occurring during processing of drug is the differential scanning cal- orimetry (DSC) [10–12]. The aim of this study was to check the effect of radiation sterilisation on disulfiram in solid phase by DSC and spectroscopic methods. Disulfiram (Antabuse, Esperal, bisdiethylthiocarbamil disulphide) is a well-known therapeutic drug applied in treatment of alcoholism to prevent drinking alcohol by producing unpleasant side effects, such as headaches, B. Marciniec Á K. Dettlaff Department of Pharmaceutical Chemistry, Poznan University of Medical Sciences, Grunwaldzka 6, 60-780 Poznan ´, Poland M. Naskrent Department of Medical Physics, Faculty of Physics, A. Mickiewicz University, Umultowska 85, 61-614 Poznan ´, Poland Z. Pietralik Á M. Kozak (&) Department of Macromolecular Physics, Faculty of Physics, A. Mickiewicz University, Umultowska 85, 61-614 Poznan ´, Poland e-mail: mkozak@amu.edu.pl 123 J Therm Anal Calorim (2012) 108:33–40 DOI 10.1007/s10973-011-1810-4