Abstract: A validated simple, rapid, and selective spectrofluorimetric method was developed for the
determination of some non-sedating antihistamines (NSAs); namely cetirizine (CTZ), ebastine (EBS),
fexofenadine (FXD), ketotifen (KET), and loratadine (LOR). The method is based on quenching effect of the cited drugs on the fluorescence intensity of erythrosine B (EB) by the formation of ion-pair complex measured without extraction at lex.. 311 nm/ lex.. 555 nm against a reagent blank. The fluorescence intensity of EB was diminished when the studied drugs were added. There was a linear relationship between the fluorescence quenching value of the system (ΔF = F EB – F Drug–EB) and the concentration of the investigated drug. Under the
optimal conditions, the linear ranges of calibration curves for the determination of the studied NSAs were 0.25–2.0, 0.25–3.0, and 0.25–6.0
g/mL for (CTZ, KET, LOR), (EBS), and (FXD), respectively. The factors
affecting the formation of the ion-pair complex were carefully studied and optimized. The method was validated according to ICH guidelines. The suggested method is applicable for the determination of the five investigated drugs in bulk and pharmaceutical dosage forms with excellent recoveries (98.23-103.77 %).