Rudy Bonfilio

Multivariate optimization and validation of an analytical methodology by RP-HPLC for the determination of losartan potassium in capsules

This paper describes the optimization and validation of an analytical methodology for the determination of losartan potassium in capsules by HPLC using 2(5-1) fractional factorial and Doehlert designs. This multivariate approach allows a considerable improvement in chromatographic performance using fewer experiments, without additional cost for columns or other equipment. The HPLC method utilized potassium phosphate buffer (pH 6.2; 58 mmol L(-1))-acetonitrile (65:35, v/v) as the mobile phase, pumped at a flow rate of 1.0 mL min(-1). An octylsilane column (100 mm x 4.6mm i.d., 5 microm) maintained at 35 degrees C was used as the stationary phase. UV detection was performed at 254 nm. The method was validated according to the ICH guidelines, showing accuracy, precision (intra-day relative standard deviation (R.S.D.) and inter-day R.S.D values <2.0%), selectivity, robustness and linearity (r=0.9998) over a concentration range from 30 to 70 mg L(-1) of losartan potassium. The limits of detection and quantification were 0.114 and 0.420 mg L(-1), respectively. The validated method may be used to quantify losartan potassium in capsules and to determine the stability of this drug.

Analytical Validation of Quantitative High-Performance Liquid Chromatographic Methods in Pharmaceutical Analysis: A Practical Approach

Analytical validation is an essential component in allowing a laboratory to ensure routine acceptable performance of analytical methods. Despite the considerable amount of important published work on this subject, diversity still prevails in the employed methodologies because validation of an analytical method depends on the specific purpose of that method. This can lead to difficulties in validation approaches and the interpretation of results. Aiming to assist in the planning of validation methods, we discuss relevant approaches of various parameters in quantitative high-performance liquid chromatographic methods and validation fields in pharmaceutical analysis. Moreover, this article provides several up-to-date examples that should be useful as an introduction to analytical validation for practical applications in academic research or the industrial sector.

A discriminating dissolution method for glimepiride polymorphs

Glimepiride, an oral antidiabetic drug, is practically insoluble in water and exists in two polymorphic forms, I and II, of which form II has higher solubility in water. Because the dissolution rate of drugs can depend on the crystal form, there is a need to develop discriminating dissolution methods that are sensitive to changes in polymorphic forms. In this work, a dissolution method for the assessment of 4 mg glimepiride tablets was developed and validated. The optimal dissolution conditions were 1000 mL of phosphate buffer (pH 6.8) containing 0.1% (w/v) of sodium dodecyl sulfate as the dissolution medium and a stirring speed of 50 rpm using a paddle apparatus. The results demonstrated that all the data meet the validation acceptance criteria. Subsequently, tablets containing forms I and II of glimepiride were prepared and subjected to dissolution testing. A significant influence of polymorphism on the dissolution properties of glimepiride tablets was observed. These results suggested that the raw material used to produce glimepiride tablets must be strictly controlled because they may produce undesirable and unpredictable effects.

Lamivudine Salts with Improved Solubilities

To optimize solubility of drugs, current strategies mainly focus on engineering and screening of smart crystal phases. Two salts of the anti-human immunodeficiency virus (HIV) drug lamivudine--namely, lamivudine hydrochloride and lamivudine hydrochloride monohydrate, were prepared in the course of screening the crystallization conditions of lamivudine duplex, an uncommon DNA-mimic, double-stranded helical structure made up of partially protonated drug pairs. Here, water solubilities of lamivudine hydrochloride, lamivudine hydrochloride monohydrate, and lamivudine duplex are reported. The aqueous solubility of this anti-HIV drug was significantly increased in both salts and also in lamivudine duplex in relation to the water solubility of lamivudine form II. In comparison with the lamivudine form II incorporated into therapeutic formulations, the drug solubility was increased at a temperature of 299 ± 2 K by factors of 1.2, 3.3, and 4.5 in lamivudine hydrochloride, lamivudine hydrochloride monohydrate, and lamivudine duplex, respectively, demonstrating that this solid-state property of lamivudine can be improved by crystal engineering strategies. Solubility profiles were understood on the basis of structural and solvent-solute interaction approaches. At last, correlations between solubility and crystal structures allowed for a rational approach to understand how this physicochemical feature could be enhanced by engineering new salts of the drug.

Dissolution test optimization for meloxicam in the tablet pharmaceutical form

Meloxicam is a broadly used drug in the therapeutics for the osteoarthritis and rheumatoid arthritis treatments in adults, and it is available in the Brazilian market, as tablet and capsule pharmaceutical forms. The present work aimed to establish conditions for accomplishment of the dissolution test of 15 mg meloxicam tablets (A and B test products), compared with the reference product, since there is no monograph about dissolution assays for meloxicam in official summaries. To optimize the conditions several parameters were tested and, according to obtained results, the use of pH 7.5 phosphate buffer (900mL, at 37 ± 0.5oC) as dissolution medium, paddle method (apparatus 2), stirring speed of the dissolution medium at 100 rpm and collect time of 60 minutes were considered satisfactory. The samples were quantified by UV spectrophotometric method at 362 nm. The products presented kinetics of first-order. Dissolution efficiency values were of 83.25, 83.73 and 88.10% for the A, B and reference products, respectively. Factors f1 and f2 were calculated and similarity of the tested medicines was demonstrated. The dissolution test was validated presenting selectivity, linearity, precision and accuracy within of the acceptance criteria.

The form II of the antihypertensive drug chlorthalidone

Racemic mixtures of chlorthalidone (CTD) have been structurally elucidated in three crystal forms (space group P), namely, Form I, Form III (both true polymorphs) and a chloroform solvate. Here, we have structurally characterized the Form II, which, in contrast to the known forms, individual crystals are pure enantiomers. However, the Form II bulk product from spontaneous chiral resolution upon crystallization contains a mixture of crystals as a conglomerate, half of which consists solely of the (R)-enantiomer, the other half the (S)-enantiomer. Form II was solved in the space group P21 with one (R)-enantiomer unit in its asymmetric unit resembling that of Form III in terms of the chlorobenzenesulfonamide moiety conformation. Even though the (R)-enantiomer has been chosen for the single-crystal structure determination experiment, chiral chromatography and optical rotation data have inferred the conglomerate nature of Form II. Concerning the crystal packing of Form II, all hydrogen bonding functionalities of the sulfonamide group are saturated into the assembly of helical ribbons growing along the [010] direction, a supramolecular motif which is not found in the known crystal phases of the drug. Moreover, Form II shows packing similarity to the chloroform solvate mainly because the hydrogen bonding patterns of their isoindolinyl functionalities. The isoindolinyl stacking also occurs similarly in Form II and in the solvate form, with bends between the planes calculated through those moieties of stacked molecules of ca. 28° and 24°. In summary, we believe that the structural knowledge of Form II concerns new outlooks not only into the solid-state properties of CTD but also into its medicinal chemistry, e.g., regarding pharmacological profiles of the conglomerate.

Development and validation of an UV-derivative spectrophotometric method for determination of glimepiride in tablets

Glimepiride is an oral antidiabetic drug widely used in treatment of type 2 diabetes. This work proposed the development and validation of a derivative UV spectrophotometric method for determination of glimepiride in tablets. The quantification of glimepiride in 5×10-3 mol L-1 NaOH was performed by using a wavelength interval of 8 nm in the range of 220-300 nm. The amplitude values obtained in the second-derivative spectra were arbitrary units of the peak height from the central zero base line to the signals obtained at 279.0, 257.5 and 256.3 nm for quantification of Amaryl® tablets 1 mg, Amaryl® tablets 2 mg and Amaryl® tablets 4 mg, respectively. The method was completely validated according to the International Conference on Harmonization (ICH) guidelines, showing accuracy, precision, selectivity, robustness and linearity. The validated method is suitable for quality control applications, since it does not use polluting reagents, it is simple and has low-cost.

A Review of Analytical Techniques for Determination of Glimepiride: Present and Perspectives

Glimepiride is an oral antidiabetic drug in the sulfonylurea class, which is widely used in treatment of Type 2 diabetes and it is currently available in more than 60 countries worldwide. As a result of the importance of this oral hypoglycemic agent in the treatment of noninsulin-dependent diabetes mellitus, this work aims to compile the published analytical methods reported so far in the literature for determination of glimepiride in biologic samples and pharmaceutical formulations. Techniques like high-performance liquid chromatography with ultraviolet, array-diode, mass spectroscopy, evaporative light scattering and charged aerosol detections, liquid chromatography-atmospheric pressure chemical ionization-mass spectrometry, liquid chromatography-electrospray ionization-tandem mass spectrometry, semimicrobore high-performance liquid chromatography with column-switching, micellar electrokinetic chromatography, high-performance thin layer chromatography, polarography, and spectrophotometry have been used for analysis, from which it can be seen that high-performance liquid chromatography methods have been used most extensively.

Comparative study of analytical methods by direct and first-derivative UV spectrophotometry for evaluation of losartan potassium in capsules

Losartan potassium is an antihypertensive non-peptide agent, which exerts its action by specific blockade of angiotensin II receptors. The aim of the present study was the validation and application of analytical methods for the quality control of losartan potassium 50 mg in pharmaceutical capsules, using direct and first-derivative UV spectrophotometry. Based on losartan potassium spectrophotometric characteristics, a signal at 205 nm of the zero-order spectrum and a signal at 234 nm of the first-derivative spectrum, were found adequate for quantification. The results were used to compare these instrumental techniques. The linearity between the signals and concentrations of losartan potassium in the ranges of 3.0-7.0 mg L-1 and 6.0-14.0 mg L-1 for direct and first-derivative spectrophotometry in aqueous solutions, respectively, presented a correlation coefficient (r) of 0.9999 in both cases. The methods were applied for losartan potassium in capsule dosage obtained from local pharmacies, and were shown to be efficient, easy to apply and low cost. These methods do not use polluting reagents and require relatively inexpensive equipment.

A Dissolution Test for Finasteride in Immediate-Release Capsules

In vitro dissolution tests for solid oral dosage forms are extremely important to ensure the quality of these products. However, no dissolution test has been reported for finasteride (FNS) in immediate-release capsules. The aims of this work were to optimize a dissolution method for FNS capsules, validate the analytical method, and evaluate three different commercial products. The best in vitro dissolution profile was achieved using water as the dissolution medium with a basket stirrer at 100 rpm. The quantitative determination was performed by high performance liquid chromatography (HPLC) at 210 nm. All validation parameters were satisfactory. The application of the method to commercial products showed the discriminatory power of the dissolution method. Because there is no monograph for FNS in capsules, this study illustrates the importance of an official dissolution test for FNS in capsules and the need to standardize the composition of the excipients contained in these commercial products. INTRODUCTION In vitro dissolution tests for immediate-release solid oral dosage forms, such as tablets and capsules, are extremely important because these tests are essential to evaluate the lot-to-lot quality of a drug product, to guide the development of new formulations, and to ensure continuing product quality and performance after certain changes (e.g., formulation, manufacturing process, site of manufacture, and scale-up of the manufacturing process) (1). For these reasons, progressively more emphasis has been placed on dissolution testing within the pharmaceutical industry and by regulatory authorities (2). Despite the importance of dissolution tests in ensuring the quality of medicines, several drug products that are widely commercialized throughout the world lack official dissolution tests. Finasteride (FNS) is a relevant example because no dissolution test is reported in the literature or in pharmacopeias for immediate-release capsules of this medication. FNS capsules are widely marketed and are prepared for medical reasons (e.g., avoiding an excipient to which a patient is allergic or obtaining a dosage level that is not marketed). FNS is N-(1,1-dimethylethyl)-3-oxo-4-aza-5α-androst1-ene-17β-carboxamide (Figure 1), a specific competitive inhibitor of steroid type-II 5α-reductase, an intracellular enzyme that converts testosterone to dihydrotestosterone (DHT) and is widely used for the treatment of benign prostatic hyperplasia (BPH) (3), prostate cancer (4), and androgenetic alopecia (5–8). A daily dose of 5 mg has been used for the treatment of BPH and prostate cancer, and a 1-mg dose has been used for the treatment of androgenetic alopecia. FNS has a molecular formula of C23H36N2O2, a molecular weight of 372.6, and a log Po/w of 3.03. According to the Biopharmaceutics Classification System (BCS), FNS is a Class 2 drug having low solubility and high permeability (9). Multiple analytical procedures have been reported for the analysis of FNS in pharmaceutical preparations when it is present as a single active ingredient or in combination dosage forms, using spectrophotometry (10–12), thin-layer chromatography (13, 14), infrared spectrophotometry (15), polarography (16), voltammetry (17), gas chromatography (18), gas chromatography–mass spectrometry (19), high performance liquid chromatography (HPLC) (20–23), and ultra-high performance liquid chromatography (UHPLC) (24, 25). Because of the importance of in vitro dissolution tests for immediate-release solid oral dosage forms and the lack of a dissolution test for FNS compounded capsules, the aims of this work were to optimize a dissolution method *Corresponding author. e-mail: olimpia_martins@yahoo.com.br Figure 1. Chemical structure of finasteride. dx.doi.org/10.14227/DT200313P25