Spectrofluorimetric Determination of Some H1 Receptor Antagonist Drugs in Pharmaceutical Formulations and Biological Fluids

A validated simple, economic, selective, and stability indicating spectrofluorimetric method was developed for the determination of some antihistaminic H1 receptor antagonist drugs namely ebastine (EBS), cetirizine dihydrochloride (CTZ), and fexofenadine hydrochloride (FXD). The method is based on the reaction of the cited drugs with 2-cyanoacetamide in alkaline medium to give highly fluorescent derivatives measured at 365 nm after excitation at 312 nm. The method was applied for the determination of the studied drugs in their dosage forms. Furthermore, the method was applied for the determination of the drugs in spiked human plasma, and used to reveal the pharmacokinetic characters in a healthy volunteer treated with oral administration of the different dosages of the drugs. The method was utilized to investigate the kinetics of the alkaline, acidic, oxidative, and ultraviolet degradation of the drugs. The apparent first order rate constants and half life times of the degradation products were calculated. INTRODUCTION: Ebastine; (4 ́tert.-butyl4[4(diphenylmethoxy)piperidino] butyrophenone (Fig. 1), cetirizine dihydrochloride; (±)[2[4[(4chlorophenyl) phenylmethyl] 1piperazinyl] ethoxy]acetic acid (Fig. 2), and Fexofenadine hydrochloride; α, α dimethyl-4[1hydroxy4[4(hydroxydiphenyl-methyl)-1 piperidinyl]butyl]-benzene acetic acid (Fig. 3) are potent long acting antihistaminic H1 receptor antagonist drugs .