Development and validation of a capillary electrophoretic method for the determination of amiodarone and desethylamiodarone

Herb-drug interaction of Fucus vesiculosus extract and amiodarone in rats: a potential risk for reduced bioavailability of amiodarone in clinical practice

Fucus vesiculosus is a seaweed claimed to be useful for obesity management. Therefore, considering the relationship between obesity and cardiovascular diseases, this work aimed to assess the potential for an herb-drug interaction among a standardized F. vesiculosus extract (GMP certificate) and amiodarone (a narrow therapeutic index drug) in rats. In a first pharmacokinetic study, rats were simultaneously co-administered with a single-dose of F. vesiculosus (575 mg/kg, p.o.) and amiodarone (50 mg/kg, p.o.); in a second study, rats were pre-treated during 14 days with F. vesiculosus (575 mg/kg/day, p.o.) and received amiodarone (50 mg/kg, p.o.) on the 15th day. Rats of the control groups received the corresponding volume of vehicle. After analysis of the pharmacokinetic data it deserves to be highlighted the significant decrease in the peak plasma concentration of amiodarone (55.4%) as well as the reduction of systemic exposure to the parent drug (~30%) following the simultaneous co-administration of F. vesiculosus extract and amiodarone. This paper reports, for the first time, the herb-drug interaction between F. vesiculosus and amiodarone, which determined a considerable decrease on amiodarone bioavailability in rats. Therefore, the therapeutic efficacy of amiodarone may be compromised by the concurrent administration of herbal slimming medicines/dietary supplements containing F. vesiculosus.

Herb-Drug Interaction of Paullinia cupana (Guarana) Seed Extract on the Pharmacokinetics of Amiodarone in Rats

Paullinia cupana is used in weight-loss programs as a constituent of medicinal/dietary supplements. This study aimed to assess a potential herb-drug interaction among a standardized (certified) Paullinia cupana extract and amiodarone (narrow therapeutic index drug) in rats. In a first pharmacokinetic study rats were simultaneously coadministered with a single dose of Paullinia cupana (821 mg/kg, p.o.) and amiodarone (50 mg/kg, p.o.), and in a second study rats were pretreated during 14 days with Paullinia cupana (821 mg/kg/day, p.o.) receiving amiodarone (50 mg/kg, p.o.) on the 15th day. Rats of the control groups received the corresponding volume of vehicle. Blood samples were collected at several time points after amiodarone dosing, and several tissues were harvested at the end of the experiments (24 h after dose). Plasma and tissue concentrations of amiodarone and its major metabolite (mono-N-desethylamiodarone) were measured and analysed. A significant reduction in the peak plasma concentration (73.2%) and in the extent of systemic exposure (57.8%) to amiodarone was found in rats simultaneously treated with Paullinia cupana and amiodarone; a decrease in tissue concentrations was also observed. This paper reports for the first time an herb-drug interaction between Paullinia cupana extract and amiodarone, which determined a great decrease on amiodarone bioavailability in rats.

Flow injection chemiluminescent determination of amiodarone in pharmaceutical preparations using photogenerated tris(2,2′-bipyridyl)ruthenium(III)

A flow injection configuration was developed and evaluated for the chemiluminescent determination of amiodarone. The method is based on the reaction of the drug with tris(2,2'-bipyridyl)ruthenium(III), which was generated through the on-line photo-oxidation of tris(2,2'-bipyridyl)ruthenium(II) with peroxydisulfate. Under the optimum experimental conditions, a linear calibration graph was obtained over the range 3.0-60.0 microg ml(-1) with a detection limit of 0.28 microg ml(-1). The proposed method allows 120 injections h(-1) with excellent repeatability and precision (R.S.D. less than 0.5% and 2.8%, respectively) and a reagent consumption of only 0.37 micromol (0.27 mg) of Ru(bpy)(3)Cl(2) x 6H(2)O per determination. The method was successfully applied to the determination of amiodarone in commercial pharmaceutical formulations.

Development and validation of a capillary electrophoresis method with ultraviolet detection for the determination of the related substances in a pharmaceutical compound

A capillary electrophoresis (CE) method was successfully developed to quantify the impurity profile of a new substance of pharmacological interest: LAS 35917. CE method was developed in order to separate the chloromethylated, monomethylated and hydroxylated impurities (molecules with very similar chemical structures) having the three coelution in the reversed-phase LC method initially established. Taking into account the structure of the impurities of LAS 35917, separation by conventional liquid chromatography (LC) methods would be longer and tedious than separation by CE, which is an appropriate and versatile technique giving easier and quicker methods. Among the three potential impurities mentioned of LAS 35917, two are due to the synthesis route of this drug, and the third arises from degradation. These drug-related impurities were separated using a capillary of 56 cm of effective length and 50 microm I.D., a 60 mM tetraborate buffer, at pH 9.2, and a positive voltage of 20 kV. The optimised CE method was preliminary validated with regard to specificity, linearity, limits of detection and quantitation, repeatability and solution stability. The method allows the detection and quantitation of impurities above 0.04 and 0.08% level, respectively. All three related substances were separated, detected and quantified from their parent drug in the analysis of real samples of LAS 35917, stressed or not stressed, with this simple and fast CE method.