The analysis of the effect of drugs in insulin aggregation is interesting due to its influence on human metabolism. We present a method to analyse the effect of an antiretroviral drug (AZT) on the insulin aggregation, based on the principal components analysis of the infrared spectra recorded in the process. This method allows the analysis of the conformational changes involved in the aggregation, providing a time value associated with the aggregates formation. The analysis was performed using Zn-free insulin in buffered solution at 1.72 mM concentration. The aggregation was monitored in situ by FTIR at 37 degrees C and the dependence of the concentration of AZT was considered, contemplating three concentration levels of AZT. The interaction between AZT and insulin was proved by (HNMR)-H-1 spectroscopy. The aggregation states were characterised by solubility tests and microscope imaging. A comparative analysis of time aggregation led observing that the process was delayed when the concentration of AZT was lower than 1.72 mM, while it accelerated at equal or higher concentrations. This dependence was related to the concentration of the monomeric species in the medium. The analysis was performed in serum to evaluate the influence of serum proteins in the phenomena, concluding that AZT binds to insulin before than to serum proteins. (C) 2012 Elsevier B.V. All rights reserved.