The aim of the present study is to present the different reactivity of azithromycin and clarithromycin (pure and commercial) at a gold electrode in neutral electrolyte using cyclic linear sweep voltammetry under the same experimental conditions. A gold electrode was successfully used for the electrochemical qualitative and quantitative determination of azithromycin dihydrate and azithromycin from capsules (Hemomycin®) and for the separation of azithromycin from one of the excipients, lactose monohydrate. The good catalytically activity of the gold electrode was employed only for the qualitative electrochemical determination of pure clarithromycin by appearance of one cathodic and four anodic reactions, which enabled structural changes in this molecule during electrochemical reactions to be studied. Commercial clarithromycin, Clathrocyn® was qualitative determined by one reproducible anodic reaction. The activity of one of the excipients, Avicel, observed as a cathodic peak at different potential from the cathodic peak obtained with pure clarithromicin was used for the determination of its presence in Clathrocyn® tablets. FTIR Analysis showed the apparent changes in structure of pure clarithromycin, as well as in the molecule of clarithromycin in Clathrocyn® tablets. HPLC Analysis showed a significant decrease in the concentration of azithromycin, Hemomycin® clarithromycin and Clathrocyn® after the electrochemical reactions.