Development and validation of a reversed-phase liquid chromatographic method for analysis of aspirin and warfarin in a combination tablet formulation

AGREE and ESA for Greenness Assessment of a Novel Validated RP-HPLC Method for Simultaneous Determination of Aspirin, Warfarin and Clopidogrel in Rat Plasma: Application to Pharmacokinetic Study of the Possible Interaction between the Three Drugs

The green profile of the developed method is assessed and compared with previously reported methods. Percutaneous coronary intervention is a procedure where a catheter is utilized to place a stent in order to facilitate opening of the blood vessels in the heart. Triple antithrombotic therapy includes oral anticoagulation as warfarin and dual antiplatelet therapy (composed of aspirin and clopidogrel bisulfate). The aim of the current study was to evaluate the pharmacokinetic parameters of ASP, WAR and CLP and to investigate the possible interaction between the three drugs upon co-administration in rats. A selective and precise RP-HPLC method was developed for the simultaneous determination of ASP, WAR and CLP in rat plasma. Pharmacokinetic study was conducted in rats that received ASP, WAR and CLP as an application of the developed method. From the statistical evaluation of the pharmacokinetic parameters, it was observed that the co-administration of ASP, WAR and CLP significantly increased the ASP and CLP bioavailability in rats. A significant drug-drug interaction was confirmed in the current study. The elevated Cmax of ASP and CLP upon the co-administration of ASP, WAR and CLP may explain the reported bleeding.

Mini Review on Forced Degradation Studies on Anti-Epileptic Drugs and Beyond

In this review on the forced degradation studies on anti-epileptic drugs and the development of validated stability-indicating assay methods for drug substances and products at a condition more severe than accelerated condition (i.e. 40 ± 2°C, 75 ± 5% relative humidity), the drug substance and drug product undergo degradation is known as forced or stress degradation. To know about the impurities developed during the storage of drug products in various environmental conditions. The limit of degradation allowable is 5-20%. More than 20% of degradation is abnormal and must be investigated. Any regulatory guidelines do not mention the pH conditions for acid or base hydrolysis, the temperature for thermal degradation or the concentration of the oxidation agent. Only International Conference on Harmonization (ICH) guidelines Q1B photostability stability and states that light sources must be a combination of UV and visible light. The shortcomings of mentioned techniques with appreciation to regulatory necessities are highlighted. A systematic method for the forced degradation studies on anti-epileptic drugs such as "Topiramate, Vigabatrin, Lacosamide, Tiagabine, Levetiracetam and Zonisamide" is discussed. This review helps researchers to get an idea about stability-indicating methods of development and validation for newer antiepileptic drugs and the characteristics of drug products that degrade under specific degradation conditions.

Simultaneous Determination of Warfarin and Aspirin Contents in Biological Fluids Using Excitation-Emission Matrix Fluorescence Coupled with a Second-order Calibration Method

In the present work, a practical method that combines excitation-emission matrix fluorescence with a second-order calibration method based on an alternating trilinear decomposition (ATLD) algorithm was developed in order to simultaneously and directly determine the contents of warfarin (WAR) and aspirin (ASA) in human plasma and urine samples, even in the presence of unknown interferences. With the pre-estimated component number of 4, the obtained average spiked recoveries were 105.4 ± 7.8 and 104.2 ± 8.3% for WAR, 96.5 ± 2.8 and 91.2 ± 2.3% for ASA in human plasma and urine samples, respectively. Furthermore, the figures of merit were calculated and also inter- and intra-day experiments were performed that proved the proposed method is of great significance to the monitoring of clinical administration and also being a simple sample pretreatment at low-cost.

Development and Validation of RP-HPLC Method for Simultaneous Estimation of Aspirin and Esomeprazole Magnesium in Tablet Dosage Form

A simple, specific, precise, and accurate reversed-phase HPLC method was developed and validated for simultaneous estimation of aspirin and esomeprazole magnesium in tablet dosage forms. The separation was achieved by HyperChrom ODS-BP C18column (200 mm × 4.6 mm; 5.0 μm) using acetonitrile: methanol: 0.05 M phosphate buffer at pH 3 adjusted with orthophosphoric acid (25 : 25 : 50, v/v) as eluent, at a flow rate of 1 mL/min. Detection was carried out at wavelength 230 nm. The retention times of aspirin and esomeprazole magnesium were 4.29 min and 6.09 min, respectively. The linearity was established over the concentration ranges of 10–70 μg/mL and 10–30 μg/mL with correlation coefficients (r2) 0.9986 and 0.9973 for aspirin and esomeprazole magnesium, respectively. The mean recoveries were found to be in the ranges of 99.80–100.57% and 99.70–100.83% for aspirin and esomeprazole magnesium, respectively. The proposed method has been validated as per ICH guidelines and successfully applied to the estimation of aspirin and esomeprazole magnesium in their combined tablet dosage form.

Anodic Determination of Acetylsalicylic Acid at a Mildly Oxidized Boron-Doped Diamond Electrode in Sodium Sulphate Medium

Differential pulse voltammetry (DPV) and chronoamperometry (CA) were used to detect and determine acetylsalicylic acid (ASA) at a mildly oxidized boron-doped diamond (BDD) electrode in a neutral sodium sulphate solution as supporting electrolyte. ASA determination in unbuffered medium was achieved using neutralized standard and real samples. Over the concentration range of 0.01 mM–0.1 mM, linear calibration plots of anodic current peaks in DPV and anodic currents in CA experiments versus concentration were obtained with very high correlation coefficients and good sensitivity values. The limits of detection were situated around 1 μM. The association of DPV and CA techniques with standard addition method represented a suitable option for the determination of ASA in real samples such as pharmaceutical formulations.

Quantitative HPLC analysis of mebeverine, mesalazine, sulphasalazine and dispersible aspirin stored in a Venalink monitored dosage system with co-prescribed medicines

An HPLC method for the quantitative analysis of mebeverine HCl, 5-aminosalicylic acid (5-ASA), sulphasalazine and dispersible aspirin has been developed and then applied to these specific medicines when stored, with other medications, in Venalink blister packs (monitored dosage system) for periods of up to 35 days. Chromatographic separation was achieved on a reversed-phase C(12) column with an isocratic mixture of methanol, water and acetic acid as the mobile phase. The method was validated regarding: accuracy, precision, detection limits, quantification limits, specificity and robustness.

Warfarin: history, tautomerism and activity

The anticoagulant drug warfarin, normally administered as the racemate, can exist in solution in potentially as many as 40 topologically distinct tautomeric forms. Only 11 of these forms for each enantiomer can be distinguished by selected computational software commonly used to estimate octanol-water partition coefficients and/or ionization constants. The history of studies on warfarin tautomerism is reviewed, along with the implications of tautomerism to its biological properties (activity, protein binding and metabolism) and chemical properties (log P, log D, pK (a)). Experimental approaches to assessing warfarin tautomerism and computational results for different tautomeric forms are presented.

Sensitive determination of aspirin and its metabolites in plasma by LC-UV using on-line solid-phase extraction with methylcellulose-immobilized anion-exchange restricted access media

We describe a sensitive determination of aspirin (ASA) and its three metabolites (salicylic acid [SA], 2,3-dihydroxybenzoic acid [2,3-DHBA], and 2,5-dihydroxybenzoic acid [gentisic acid (GA)]) in rat plasma. Analysis was carried out by on-line solid-phase extraction (SPE) using a methylcellulose-immobilized-strong anion-exchanger (MC-SAX), followed by liquid chromatography (LC) coupled with UV detection. The lower limits of quantitation for ASA and SA were 60 ng/mL in 100 microL of plasma, respectively. This method was validated with respect to intra- and inter-day precision, accuracy, and linearity up to concentrations of 20,000 ng/mL for ASA, SA, 2,3-DHBA and gentisic acid, respectively. The method was successfully applied to an analysis of the pharmacokinetics of ASA and SA in rats.

Iron(II)-phthalocyanine as a novel recognition sensor for selective potentiometric determination of diclofenac and warfarin drugs

Construction and characterization of potentiometric membrane sensors for quantification of diclofenac and warfarin drugs are described. The membranes of the sensors incorporate 1.8 wt.% iron(II)-phthalocyanine (Pc) as a molecular recognition reagent, 64.3 wt.% dibutylsebacate (DBS) solvent mediator, 1.8 wt.% tridodecylmethylammonium chloride (TDMAC) as membrane additive and 32.1 wt.% poly(vinyl chloride) (PVC) as a matrix. The sensors display linear response for 1 x 10(-2) to 9 x 10(-6) mol l(-1) (detection limit 5.4 x 10(-6) mol l(-1)) and 1 x 10(-2) to 5 x 10(-6) mol l(-1) (detection limit 3 x 10(-6) mol l(-1)) with anionic slopes of -61 +/- 1 and -63 +/- 1 mVdecade(-1) over the pH range 5.5-9 for declofenac and warfarin, respectively. Validation of the assay methods according to the quality assurance standards confirms their suitability for quality control purposes. Use of the sensor for the assay of various formulations of the drugs shows a mean average recovery of 99.7% of the nominal values and a mean precision of +/-0.3%. Significantly improved accuracy, precision, response time, stability, selectivity and sensitivity are offered by these simple and cost-effective potentiometric sensors compared with other standard techniques.

Development of validated stability-indicating assay methods--critical review

This write-up provides a review on the development of validated stability-indicating assay methods (SIAMs) for drug substances and products. The shortcomings of reported methods with respect to regulatory requirements are highlighted. A systematic approach for the development of stability-indicating methods is discussed. Critical issues related to development of SIAMs, such as separation of all degradation products, establishment of mass balance, stress testing of formulations, development of SIAMs for combination products, etc. are also addressed. The applicability of pharmacopoeial methods for the analysis of stability samples is discussed. The requirements of SIAMs for stability study of biotechnological substances and products are also touched upon.

A validated HPLC method for the determination of pyridostigmine bromide, acetaminophen, acetylsalicylic acid and caffeine in rat plasma and urine

A method was developed for the separation and quantification of the anti-nerve agent pyridostigmine bromide (PB; 3-dimethylaminocarbonyloxy-N-methyl pyridinium bromide), the analgesic drugs acetaminophen and acetylsalicylic acid, and the stimulant caffeine (3,7-dihydro-1,3,7-trimethyl-1-H-purine-2,6-dione) in rat plasma and urine. The compounds were extracted using C(18) Sep-Pak(R) cartridges then analyzed by high performance liquid chromatography (HPLC) with reversed phase C18 column, and UV detection at 280 nm. The compounds were separated using gradient of 1-85% acetonitrile in water (pH 3.0) at a flow rate ranging between 1 and 1.5 ml/min in a period of 14 min. The retention times ranged from 8.8 to 11.5 min. The limits of detection were ranged between 100 and 200 ng/ml, while limits of quantitation were 150-200 ng/ml. Average percentage recovery of five spiked plasma samples were 70.9+/-9.5, 73.7+/-9.8, 88.6+/-9.3, 83.9+/-7.8, and from urine 69.1+/-8.5, 74.5+/-8.7, 85.9+/-9.8, 83.2+/-9.3, for pyridostigmine bromide, acetaminophen, acetylsalicylic acid and caffeine, respectively. The relationship between peak areas and concentration was linear over range between 100 and 1000 ng/ml. The resulting chromatograms showed no interfering peaks from endogenous plasma or urine components. This method was applied to analyze these compounds following oral administration in rats.

Comparison of derivative spectrophotometric and liquid chromatographic methods for the determination of omeprazole in aqueous solutions during stability studies

A first derivative spectrophotometric method was developed for the determination of omeprazole in aqueous solutions during stability studies. The derivative procedure was based on the linear relationship between the omeprazole concentration and the first derivative amplitude at 313 nm. The first derivative spectra was developed between 200 and 400 nm (deltalambda = 8). This method was validated and compared with the official high-performance liquid chromatography (HPLC) method of the USP. It showed good linearity in the range of concentrations studied (10-30 microg ml(-1)), precision (repeatability and inter-day reproducibility), recovery and specificity in stability studies. It also seemed to be 2.59 times more sensitive than the HPLC method. These results allowed to consider this procedure as useful for the rapid analysis of omeprazole in stability studies since there was no interference with its decomposition products.

Cyclodextrin-based optosensor for the determination of warfarin in waters

A flow-through optosensor for warfarin is described. The sensor is developed in conjunction with flow analysis systems and uses a commercial bound beta-cyclodextrin material as the sensing phase. A strong fluorescence signal was observed as a result of the formation of an inclusion complex between warfarin and beta-cyclodextrin. The analytical performance characteristics of the proposed sensor for analysis of low levels of warfarin were as follows: the detection limits for continuous and flow injection analysis systems were 2 and 19 ppb, respectively; the observed relative standard deviations at 0. 5 ppm warfarin level were less than 2.3%. A study of the interference of other naphthalenic toxic substances was carried out. The continuous flow method was satisfactorily applied to the determination of the rodenticide in natural waters.

Quantitative determination of dimethicone in commercial tablets and capsules by Fourier transform infrared spectroscopy and antifoaming activity test

Fourier transform infrared (FTIR) spectroscopy and antifoaming activity test have been employed for the quantitative analysis of dimethicone. Linearity, accuracy and precision are presented for both methods. These methods have been also used to compare different dimethicone-containing proprietary medicines. FTIR spectroscopy has shown to be adequate for quantitation of dimethicone in commercial tablets and capsules in order to comply with USP requirements. The antifoaming activity test is able to detect incompatibilities between dimethicone and other constituents. The presence of certain enzymes in some medicinal products increases the defoaming properties of these formulations.

Determination of aspirin and salicylic acid in transdermal perfusates

A high-performance liquid chromatographic (HPLC) method has been developed for the simultaneous determination of aspirin and salicylic acid in transdermal perfusates. The compounds were separated on a C8 Nucleosil column (5 microm, 250x4.6 mm) using a mobile phase containing a mixture of water-acetonitrile-orthophosphoric acid (650:350:2, v/v/v) and a flow-rate of 1 ml/min. The transdermal samples were in phosphate-buffered saline (PBS) and could be injected directly onto the HPLC system. The method was reproducible with inter-day R.S.D. values of no greater than 3.46 and 2.60% for aspirin and salicylic acid, respectively. The method was linear over the concentration range 0.2-5.0 microg/ml and had a limit of detection of 0.05 microg/ml for both compounds. For certain samples, it was necessary to ensure that no transmembrane leakage of the aspirin prodrugs had occurred. In these cases, a gradient was introduced by increasing the acetonitrile content of the mobile phase after the salicylic acid had eluted. The method has been applied to the determination of aspirin and salicylic acid in PBS following in vitro application of the compounds to mouse skin samples.