In this study a PVC membrane electrode for determination of ketotifen fumarate is reported, where ketotifen tetraphenylborate (Keto-TPB) was used as ion exchanger. The electrode has linear range of 5.6x10(-6)-1.0x10(-2) and 1.0x10(-5)-1.0x10(-2) mol/L, with detection limits 2.37x10(-6)and 4.60x10(-6) mol/L in batch and flow injection analysis (FIA), respectively. The electrodes show a Nernstian slope value (58.40 and 61.50 mV/decade in batch and FIA, respectively), and the response time is very short (<or=10 s). The potential is nearly stable over the pH range 2.0-8.0. Selectivity coefficient values towards different inorganic cations, sugars and amino acids reflect high selectivity of the prepared electrodes. These are used for determination of Ketotifen using potentiometric titration and standard addition methods in pure samples and its pharmaceutical preparations (Zaditen tablets and syrup). The average recovery values are 99.5 and 99.2% with RSD 1.4 and 1.2% for potentiometric titrations and standard addition methods, respectively. The electrode response at different temperatures was also studied.