Spectrophotometric Determination of Promethazine Hydrochloride in Pure and Pharmaceutical Dosage Forms Hemn A. Qader 1a) and Nabil A. Fakhre 2b) 1 Pharmaceutical Chemistry Dept., College of Pharmacy, Hawler Medical University, Erbil, Kurdistan Region, IRAQ. 2 Department of Chemistry, College of Education, Salahaddin University, Erbil, Kurdistan Region, IRAQ. a hemn.abdul@gmail.com b nabil.fakhre@su.edu.krd Abstract. A rapid and simple spectrophotometric method for the determination of promethazine HCl in pure and pharmaceutical dosage forms is described. The method is based on the oxidation of promethazine HCl with chromium trioxide in acidic medium, which produce a product having maximum absorption at 515 nm. The calibration graph showed that Beer's law is obeyed over the concentration range of 5.0 – 100.0 μg/mL, with the detection limit of 3.0 μg/mL and the molar absorptivity was 5.2 ×10 3 l/mol. cm. The precision and the accuracy were acceptable depending upon the values of relative standard deviation and error percentage. The influence of common interferences was studied and the method was applied for the estimation of promethazine HCl in different pharmaceutical formulations available in market with good recoveries. Keywords: Promethazine HCl (PH); Oxidation; Chromium Trioxide; Spectrophotometry and Pharmaceutical formulations. INTRODUCTION Promethazine hydrochloride (PH) [N,N-dimethyl-1-(10H-phenothiazine-10-yl)propan-2-amine] hydrochloride, is a first-generation antihistamine belonging to the phenothiazine family (1) , (Fig. 1). Promethazine which were introduced in the 1λ50’s as antipsychotic drugs are still widely used in the treatment of moderate to severe mental illnesses including schizophrenia (2) . The drug also is widely used as antihistaminic, antiemetic, antipruritic, analgesic and anticholinergic, and it has a strong sedative effect and anti-motion sickness. In some countries is prescribed for treatment of insomnia (1-3) . N S N Cl H FIGURE1. Chemical structure of PH