Ibrahim A. Darwish et al. | Int. J. Res. Pharm. Sci. Vol-1, Issue-1, 6-12, 2010 ©Pharmascope Foundation | www.pharmascope.org 6 Spectral investigation and analytical application of the vinylamino-substituted haloquinone derivatives of Nizatidine and Ranitidine Ibrahim A. Darwish* a , Samiha A. Hussein b , Ashraf M. Mahmoud b , Ahmed I. Hassan c a Department of Pharmaceutical Chemistry, College of Pharmacy, King Saud University, Riyadh 11451, Saudi Arabia b Department of Pharmaceutical Analytical Chemistry, Faculty of Pharmacy, Assiut University, Assiut 71526, Egypt c Department of Pharmaceutical Analytical Chemistry, Faculty of Pharmacy, Al-Azhar University, Assiut, 71524, Egypt ABSTRACT Studies were carried out, for the first time, to investigate the formation and spectral characteristics of N- vinylamino-substituted haloquinone derivatives of nizatidine and ranitidine. The reactions involved the condensa- tion of N-alkylvinylamine formed from the interaction between the free secondary amino groups in the investi- gated drugs and acetaldehyde with each of chloranil, bromanil, and 2,3-dichloronaphthoquinone. The experimen- tal conditions affecting the reactions were optimized and the characteristics of the absorption spectra of the formed colored derivatives were established. Under the optimum reaction conditions and at the max of the formed derivatives, linear relationships were found between the absorbances and the concentrations of the inves- tigated drugs in a concentration range of 10–250 g ml 1 . The limits of assays detection were 2. 1–7.77 g ml 1 . The precisions of the methods were satisfactory; the relative standard deviations were 1.13–1.73%. The proposed methods were successfully applied to the analysis of the studied drugs in pure and pharmaceutical dosage forms with good accuracy; the recovery percentages were 98.1–101.8 0.58–1.57%. The results were compared favora- bly with those of the official methods. Keywords: H 2 -receptor antagonists; Nizatidine, Ranitidine, N-Vinylamino-substituted haloquinones; Spectropho- tometry; Pharmaceutical analysis. 1. INTRODUCTION Nizatidine (NIZ), and ranitidine (RAN) (Fig. 1), are his- tamine H 2 -receptor antagonists. They competitively inhibit the action of histamine on the H 2 -receptors of parietal cells and reduce the gastric acid secretion. These drugs are used for the short term treatment of active duodenal and gastric ulcers and the hypersecre- tory conditions (e.g. Zollinger-Ellison Syndrome). They are more potent in inhibition of gastric acid secretion than other H 2 -receptor antagonists and also they are devoid of their anti-androgenic and hepatic microsom- al inhibiting side effects (Potter & Hollister, 2001; Mar- tindale, 2002). The methods reported for determination of NIZ and RAN in pharmaceutical preparations and/or biological fluids include spectrophotometry (Walash, 2002; Amin, 2003; Al-Ghannam & Belal, 2002; Hassan, 2002; Wa- lash, 2004; El-Yazbi, 2003), electrochemical-based me- thods (Norouzi, 2007), HPTLC (Kelani, 2002), HPLC (Yousef, 2006), capillary electrophoresis (Perez-Ruiz, 2002), and chemiluminometry (Tang, 2007). Spectrophotometry, because of its inherent simplicity, low cost, and wide availability of the technique in qual- ity control laboratories, is considered the most conve- nient analytical technique for the analysis of pharma- www.ijrps.pharmascope.org ISSN: 0975-7538 Research Article * Corresponding Author Email: idarwish@ksu.edu.sa Contact: +966-14677348, Fax: +966-14676220 Received on: 04-10-2009 Revised on: 10-12-2009 Accepted on: 14-12-2009 S N CH 2 SCH 2 CH 2 NH C NHCH 3 CHNO 2 N H 3 C CH 3 Nizatidine (NIZ) O CH 2 SCH 2 CH 2 NH C NHCH 3 CHNO 2 N CH 3 H 3 C Ranitidine (RAN) Fig. 1. Chemical structures of nizatidine and ranitidine