Graphene is ideally suited for implementation in electrochemical applications due to its reported large electrical conductivity, large surface area, unique heterogeneous electron transfer rate, and low production cost. This paper presents a method for the construction of graphene paste electrode (GPE) from reduced graphene oxide (RGO). Direct electrochemical detection of drug is of high importance in analytical chemistry. Here, the GPE was successfully used for the determination of acetazolamide (ACZ). So, the influence of some experimental variables such as working solution pH, supporting electrolyte, scan rate, pulse amplitude, and possible interferences were studied. The proposed sensor exhibited a high sensitivity and good selectivity, and it was applied for clinical evaluation of ACZ. (C) 2012 Elsevier B.V. All rights reserved.