Spectrofluorimetric determination of certain adrenergic agonist drugs in their pure forms and pharmaceutical formulations: Content uniformity test application.

A new, simple, sensitive and rapid spectrofluorimetric method has been developed for determination of certain adrenergic agonists such as isoxsuprine hydrochloride, ritodrine hydrochloride and etilefrine hydrochloride in their pure forms and pharmaceutical dosage forms. The method depends on micellar enhancement of the native fluorescence of investigated drugs by using 2% w/v sodium dodecyl sulfate (SDS) as an anionic surfactant. The enhanced fluorescence intensity of investigated drugs was measured at 305 nm after excitation at 278 nm. The interaction of studied drugs with SDS was studied, and the enhanced fluorescence intensity was exploited to develop an assay method for the determination of investigated drugs. The relative fluorescence intensity-concentration plots were rectilinear over the range 0.15-3.00 µg ml-1 , with low quantification limits of 0.132, 0.123 and 0.118 µg mL-1 for isoxsuprine, ritodrine and etilefrine, respectively. The proposed method was successfully applied for determination of studied drugs in their pharmaceutical formulations. Moreover, the high sensitivity of the proposed method allows performing the content uniformity testing of the studied drugs in their tablets by using the official United States Pharmacopeia (USP) guidelines. Statistical comparisons of the results with those of the reported methods revealed excellent agreement and indicated no significant difference in accuracy and precision.

Determination of phenolic sympathomimetic drugs in pharmaceutical samples and biological fluids by flow-injection chemiluminescence.

A rapid and highly sensitive flow-injection chemiluminometric method was developed for determination of 3 sympathomimetic drugs, namely, etilefrine hydrochloride, isoxsuprine hydrochloride, and prenalterol hydrochloride. The method is based on chemiluminescence induced by oxidation of drugs with acidified potassium permanganate in the presence of formic acid as a carrier. The calibration graphs were linear over the concentration ranges 0.2-9, 0.2-12.5, and 0.025-1.25 microg/mL for the 3 compounds, respectively. The method was applied successfully in determining the drugs in dosage forms and in biological fluids. A proposal for the reaction pathway is suggested.

Sequential injection spectrophotometric determination of etilefrine hydrochloride.

A simple, fast, economical and automated sequential injection spectrophotometric method for the determination of etilefrine hydrochloride is developed. The method is based on the condensation reaction of etilefrine hydrochloride with 4-aminoantipyrine in the presence of alkaline potassium hexacyanoferrate and the absorbance of the colored product measured at 503 nm. Aspiration order, flow rate, reaction coil diameter, reaction coil length, concentration of 4-aminoantipyrine and potassium ferricyanide, as well as aspiration volume of reagents and sample has been optimized. Using these optimized parameters, a linear relationship between the relative peak height and concentration was obtained in the range 1-20 mg l(-1). The detection limit (as 3sigma value) was 0.1 mg l(-1) and precision was 2.7% and 1.5% at 1 and 2 mg l(-1), respectively. This method is superior over previously reported ones in terms of linear range, short analysis time, high sample throughput, excellent reagent economy and minimum waste generation.

Spectrophotometric determination of etilefrine hydrochloride and ritodrine hydrochloride through nitrosation and subsequent cobalt chelation.

A simple and rapid method for the determination of etilefrine hydrochloride and ritodrine hydrochloride, either in pure form or in pharmaceutical formulations, is described. The method is based on the development of red product in presence of sodium nitrite and cobalt(II) salt in acid medium. The reaction is thought to proceed via preliminary nitrosation of the phenolic nucleus followed by formation of the chelate in presence of cobalt(II) salt. The highly colored chelates showed wavelengths of maximum absorption of 570 and 560 nm for etilefrine hydrochloride and ritodrine hydrochloride, respectively. The reaction product showed apparent molar absorptivities of 938 and 2930 L mol-1 cm-1 for etilefrine hydrochloride and ritodrine hydrochloride, respectively. A linear correlation was found between absorbance (at the lambda max) and concentration in ranges of 0.08-0.20 and 0.04-0.10 mg ml-1 for etilefrine hydrochloride and ritodrine hydrochloride, respectively. At the same time, the resulting colors were well developed within 25 min at boiling water bath temperature and were stable for more than 1 hr. Results of analysis of pure drugs and their dosage forms by the proposed method were in good agreement with either a reported derivative spectrophotometric procedure or the USP XXII method for etilefrine hydrochloride and ritodrine hydrochloride, respectively. The validity of the method was further confirmed using the standard addition method. The proposed method demonstrate high percentage of recovery with good accuracy and precision.

Formation of a direct mutagen, diazo-N-nitrosoetilefrin, by interaction of etilefrin with nitrite.

Reaction of an antihypotensive drug, etilefrin [alpha-[(ethylamino)methyl]-m-hydroxybenzyl alcohol], with nitrite under mildly acidic conditions produced N-nitrosoetilefrin [alpha-[(N-nitrosoethylamino)methyl]-m-hydroxybenzyl alcohol] (a mixture of syn and anti forms) (Iab) and diazo-N-nitrosoetilefrin [1-(4-diazo-3-oxo-1,5-cyclohexadienyl-2-(N-nitrosoethylamino )ethanol] (a mixture of syn and anti forms) (IIab). Treatment of etilefrin with an equivalent amount of nitrite at pH 3 and 37 degrees C for 4 h gave Iab (yield, 30%) and IIab (yield, 5%). Treatment of etilefrin with 4 eq of nitrite under the same conditions gave Iab (23%) and IIab (53%). Compounds Iab and IIab were each composed of two isomers due to the configuration of the N-nitroso group. While compound Iab was not mutagenic, compound IIab showed mutagenicity to Salmonella typhimurium TA98 and TA100 strains without metabolic activation. Specific mutagenic activity of IIab was 300 his+ revertant colonies for both TA98 and TA100 strains with a dose of 0.1 mumol. Addition of a microsomal activation system little affected the activity. It is noteworthy that this orally administered drug can produce a direct-acting mutagen by reaction with nitrite, which is present in the digestive tract.