An empirical spectrophotometric method for the determination of five antihistamines is carried out. The method is based on formation of a 1:1 charge transfer complex of promethazine, diphenhydramine, desloratadine, levocetirizine and loratadine with curcumin. Association between antihistamines and curcumin was confirmed by FT-IR spectroscopy. Method showed linear calibration curves over the range 20-140, 32-128, 18-126, 22-154 and 35-107 μg mL-1 respectively with correlation coefficient greater than 0.9981. The reliability of method was conferred by satisfactory recovery values greater than 98.45%. Moreover, the spectral characteristics including oscillator’s strength, dipole moment, ionization potential, resonance energy and the thermodynamic parameters (association constant and Gibb’s free energy changes) were investigated. The implementation of proposed method can help analysis of antihistaminic drugs in pharmaceutical formulations without interference of excipients.

Saman Naeem, Saeeda Nadir Ali, Amtul Qayoom, Haji Muhammad Urooj Haroon and Shazia Nisar