Spectrophotometric determination of fenoterol hydrobromide in pure form and dosage forms

Utility of Europium ion characteristic peak for quantitation of Fenoterol hydrobromide and Salmeterol xinafoate in different matrices; application to stability studies

A simple selective luminescent dependent approach was established for quantitation of two selective β₂ agonists namely; Fenoterol hydrobromide (FEN) and Salmeterol xinafoate (SAL). This approach utilizes the capability of the cited drugs to undergo a complexation reaction with Europium ion (Eu³⁺) in the presence of 1,10-phenanthroline as a co-ligand. The resultant complex leads to a hypersensitive transition and enhancement of the Eu³⁺ emission peak at 615nm (279nm excitation). Under the optimized conditions, the rectilinear concentration plots of both drugs were (70-1500ngmL^-1) and (100-2000ngmL^-1) with limit of quantitation 51.3 and 84.4ngmL^-1 for FEN and SAL, respectively. The luminescence properties of the complex and its optimum formation conditions were carefully investigated according to the regulations of ICH and the method was successfully applied in plasma. The good accuracy and selectivity of the suggested method allowed extending the proposed protocol into stability study of the cited drugs.

New enhanced spectrofluorimetric approach for picogram detection of Fenoterol hydrobromide through Von Pechman synthesis of coumarins

A new, specific, precise and very sensitive spectrofluorimetric methodology has been established and approved for determination of Fenoterol hydrobromide (FEN) in its pharmaceutical forms and spiked plasma. The strategy utilized the phenolic nature of FEN and its capacity to undergo Von Pechman synthesis of coumarin. In this study, Fenoterol hydrobromide reacts with ethyl acetoacetate in presence of concentrated sulfuric acid to form an extremely fluorescent coumarin derivative measured at 480 nm (λ_ex: 420 nm). Different reaction variables affecting development and stability of the formed coumarin derivative were precisely examined and enhanced to guarantee greatest sensitivity of the strategy. The recommended procedure was found to obey Beer's law in concentration range of (300-2000) pg mL^-1 with quantitation limit 130 pg mL^-1, revealing high sensitivity of the suggested method. The proposed procedure was completely examined and approved through the ICH guidelines and was efficiently applied for the determination of the cited drug in spiked plasma and its dosage forms.

Novel kinetic spectrophotometric method for estimation of certain biologically active phenolic sympathomimetic drugs in their bulk powders and different pharmaceutical formulations

A simple, selective and sensitive kinetic spectrophotometric method was described for estimation of four phenolic sympathomimetic drugs namely; terbutaline sulfate, fenoterol hydrobromide, isoxsuprine hydrochloride and etilefrine hydrochloride. This method is depended on the oxidation of the phenolic drugs with Folin-Ciocalteu reagent in presence of sodium carbonate. The rate of color development at 747-760nm was measured spectrophotometrically. The experimental parameters controlling the color development were fully studied and optimized. The reaction mechanism for color development was proposed. The calibration graphs for both the initial rate and fixed time methods were constructed, where linear correlations were found in the general concentration ranges of 3.65×10^-6-2.19×10^-5molL^-1 and 2-24.0μgmL^-1 with correlation coefficients in the following range 0.9992-0.9999, 0.9991-0.9998 respectively. The limits of detection and quantitation for the initial rate and fixed time methods were found to be in general concentration range 0.109-0.273, 0.363-0.910 and 0.210-0.483, 0.700-1.611μgmL^-1 respectively. The developed method was validated according to ICH and USP 30 -NF 25 guidelines. The suggested method was successfully implemented to the estimation of these drugs in their commercial pharmaceutical formulations and the recovery percentages obtained were ranged from 97.63%±1.37 to 100.17%±0.95 and 97.29%±0.74 to 100.14±0.81 for initial rate and fixed time methods respectively. The data obtained from the analysis of dosage forms were compared with those obtained by reported methods. Statistical analysis of these results indicated no significant variation in the accuracy and precision of both the proposed and reported methods.

Spectrophotometric and spectrofluorimetric methods for determination of certain biologically active phenolic drugs in their bulk powders and different pharmaceutical formulations

Two simple and sensitive spectrophotometric and spectrofluorimetric methods for the determination of terbutaline sulfate, fenoterol hydrobromide, etilefrine hydrochloride, isoxsuprine hydrochloride, ethamsylate, doxycycline hyclate have been developed. Both methods were based on the oxidation of the cited drugs with cerium (IV) in acid medium. The spectrophotometric method was based on measurement of the absorbance difference (ΔA), which represents the excess cerium (IV), at 317nm for each drug. On the other hand, the spectrofluorimetric method was based on measurement of the fluorescent of the produced cerium (III) at emission wavelength 354nm (λ_excitation=255nm) for the concentrations studied for each drug. For both methods, the variables affecting the reactions were carefully investigated and the conditions were optimized. Linear relationships were found between either ΔA or the fluorescent of the produced cerium (III) values and the concentration of the studied drugs in a general concentration range of 2.0-24.0μgmL^-1, 20.0-24.0ngmL^-1 with good correlation coefficients in the following range 0.9990-0.9999, 0.9990-0.9993 for spectrophotometric and spectrofluorimetric methods respectively. The limits of detection and quantitation of spectrophotometric method were found in general concentration range 0.190-0.787 and 0.634-2.624μgmL^-1respectively. For spectrofluorimetric method, the limits of detection and quantitation were found in general concentration range 4.77-9.52 and 15.91-31.74ngmL^-1 respectively. The stoichiometry of the reaction was determined, and the reactions pathways were postulated. The analytical performance of the methods, in terms of accuracy and precision, were statistically validated and the results obtained were satisfactory. The methods have been successfully applied to the determination of the cited drugs in their commercial pharmaceutical formulations. Statistical comparison of the results with the reference methods showed excellent agreement and proved that no significant difference in the accuracy and precision.