Electrochemical oxidation of loop diuretic furosemide (4-chloro-2-(furan-2-ylmethylamino)-5-sulfamoylbenzoic acid) was studied in 5.0 pH with 0.04 M Britton-Robinson buffer as supporting electrolyte at 25 +/- 0.1 degrees C at a multi-walled carbon nanotubes-paraffin oil paste electrode (CNTPE) using cyclic and differential-pulse voltammetric (DPV) techniques. The electrochemical process was observed to be adsorption controlled, irreversible and involving two-electron oxidation. Effects of anodic peak potential (E-pa), anodic peak current (I-pa) and heterogeneous rate constant (k(0)) have been discussed. Under optimal conditions, the peak current was proportional to furosemide concentration in the range of 8.0 x 10(-6) to 2.0 x 10(-4) M with a detection limit of 2.9 x 10(-7) M by differential pulse voltammetry. A differential pulse voltammetric method with good precision and accuracy was developed for the determination of furosemide in pharmaceutical formulations and urine as a real sample. (C) 2011 Elsevier Ltd. All rights reserved.