Utility of the ion-pair formation for spectrophotometric determination of terfenadine in pure form and in some pharmaceutical formulations

Abstract

Abstract.A spectrophotometric procedure for the determination of terfenadine and a number of its pharmaceutical preparations has been developed that offers advantages of simplicity, rapidity, sensitivity and stability indication over the official USP (1995) method. The proposed method is based on the formation of ion-pairs by the reaction of terfenadine with some chromotropic acid mono-and bis-azo dyes. Different variables affecting the ion-pair formation were studied and optimized. At the maximum absorption of 557, 521,592 and 543 nm, Beer's law is obeyed in the range 0.2-18.6, 0.2-16.4, 0.2-25.0 and 0.2-22.2 lag m1-1 on using reagents I, II, III and IV, respectively. The stoichiometxic ratio and stability of each ion-pair were estimated and the mechanism of the reaction is discussed. The molar absorptivity and Sandell sensitivity of the produced ion-pairs were calculated in addition to Ringbom optimum concentration ranges. Statistical treatment of the experimental results indicates that the procedures are precise and accurate. Excipients used as additives in pharmaceutical formulations did not interfere in the proposed procedures. The reliability of the methods was established by parallel determination against the official USP method. The procedures described were successfully applied to the determination of the bulk drug and its pharmaceutical formulations by applying the standard addition technique.Key words: terfenadine determination, spectrophotometry, chromotropic acid, mono-and bis-azo compounds.* To whom correspondence should be addressed Terfenadine, 1-(4-tert-butylphenyl)-4-[4-(c~-hydroxybenzhydryl) piperidin] butan-l-ol [50679-08-8], is a specific non-sedating antagonist of histamine receptors which is devoid of central nervous activity in both animals and human [1]. The antihistamine profile of terfenadine along with its pharmacodynamic properties and therapeutic efficiency were reviewed [2]. The fate of the drug in the body was followed by measuring its plasma concentration using radioimmuno-assay. The excreted drug in faeces was detected by applying the 14C analysis while the metabolic products in urine were determined by gas chromatography-mass spectrometry [3]. Recently more routine oriented analytical methods using high performance liquid chromatographic [4][5][6][7] and spectrophotometric techniques [8][9][10] were reported. The tacky nature of the terfenadine in most of the organic solvents made the drug solution handling rather difficult resulting in tedious and time consuming procedures. Consequently, more accessible economical routine testing methods for the starting material and dosage forms are appreciated.In a previous work, the ion-pair complex formation methods were described to determine other pharmaceutical drugs [11][12][13][14], but no methods are reported for the determination of terfenadine in pure form and in pharmaceutical formulations depending on this idea.Chromotropic acid (4,5-dihydroxynaphthalene-2,7 disulphonic acid) azo dyes are very famous indicators for the spectroph...

Utility of Extracted Colored Ion – Associate Complexes Formation Reaction for the Determination of Fexofenadine Hydrochloride in Pure Forms and in Dosage Forms

“…BPB, BTB, BCG and BCP have been used as active reagents for the determination of different drugs [21][22][23][24][25][26][27][28][29][30]. These methods involve colored ion -associate formed between drugs and reagents and extracted with pure chloroform.…”