A novel simple, accurate, sensitive and economical spectrophotometric method has been established and validated for the determination of the antihistaminic drug, olopatadine hydrochloride in both pure form and eye drops. The spectrophotometric method is divided into three procedures (A, B & C). The method is based on the oxidation of the studied drug by a known excess of potassium permanganate, followed by measuring the decrease in absorption (âÂÂÂÃ?â??Ã?Ë?ÂÂÂÃ?â??Ã?â? A) of KMnO4 in acidic medium (A) or basic medium (B) or measuring the increase in absorption of added methyl orange in the same basic medium (C) at wavelengths of 526, 547 and 523 nm, respectively. The detection limit is reported to be 1.05, 0.62 and 0.40 µg/mL for procedures A, B and C respectively showing a high degree of sensitivity. The proposed method was successfully validated according to FDA guidelines for the determination of the drug in eye drops with a highly precise recovery and very low relative standard deviation. Finally, the method was compared statistically with a reference method showing equal accuracy, reproducibility and no significant difference with the reported one.
