A Dissolution Test for Finasteride in Immediate-Release ...

1 A Dissolution Test for Finasteride in Immediate-Release Capsules Olimpia Maria Martins Santos*, Ana Laura Ara jo Santos, e-mail: Gislaine Ribeiro Pereira, Rudy Bonfilio, and Magali Benjamim de Ara jo Faculdade de Ci ncias Farmac uticas, Universidade Federal de Alfenas, Rua Gabriel Monteiro da Silva, 700, 37130 000, Alfenas MG, Brazil ABSTRACT. In vitro Dissolution tests for solid oral dosage forms are extremely important to ensure the quality of these products. How- ever, 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.

2 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 C23H36N2O2, a molecular weight of , and a log Po/w I. n vitro Dissolution tests for Immediate-Release solid oral of According to the Biopharmaceutics Classification dosage forms, such as tablets and capsules, are ex- System (BCS), FNS is a Class 2 drug having low solubility tremely important because these tests are essential to and high permeability (9). evaluate the lot-to-lot quality of a drug product, to guide Multiple analytical procedures have been reported for the development of new formulations, and to ensure the analysis of FNS in pharmaceutical preparations when continuing product quality and performance after certain it is present as a single active ingredient or in combination changes ( , formulation, manufacturing process, site of dosage forms, using spectrophotometry (10 12), thin-lay- manufacture, and scale-up of the manufacturing process) er chromatography (13, 14), infrared spectrophotometry (1).

3 For these reasons, progressively more emphasis has (15), polarography (16), voltammetry (17), gas chromatog- been placed on Dissolution testing within the pharmaceu- raphy (18), gas chromatography mass spectrometry (19), tical industry and by regulatory authorities (2). high performance liquid chromatography (HPLC) (20 23), Despite the importance of Dissolution tests in ensuring and ultra-high performance liquid chromatography (UH- the quality of medicines, several drug products that are PLC) (24, 25). widely commercialized throughout the world lack official Because of the importance of in vitro Dissolution tests Dissolution tests. Finasteride (FNS) is a relevant example for Immediate-Release solid oral dosage forms and the lack because no Dissolution test is reported in the literature or of a Dissolution test for FNS compounded capsules, the in pharmacopeias for Immediate-Release capsules of this aims of this work were to optimize a Dissolution method medication.

4 FNS capsules are widely marketed and are prepared for medical reasons ( , 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-5 -androst- 1-ene-17 -carboxamide (Figure 1), a specific competitive inhibitor of steroid type-II 5 -reductase, an intracellular enzyme that converts testosterone to dihydrotestoster- one (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 can- cer, and a 1 mg dose has been used for the treatment of androgenetic alopecia. FNS has a molecular formula of Figure 1. Chemical structure of Finasteride . *Corresponding author. Dissolution Technologies | AUGUST 2013. 25. for FNS capsules, validate the analytical method used for The following equipment was also used: digital pH. the quantification of the samples, and demonstrate the meter model PA 200 (Marconi , Piracicaba, S o applicability of the Dissolution test by evaluating three Paulo, Brazil), ultrasonic bath model USC 2800A (Unique, different commercial products.)

5 Indaiatuba, S o Paulo, Brazil), analytical balance Accu- lab model ALC (S o Paulo, S o Paulo, Brasil), and EXPERIMENTAL vacuum filtration system (Millipore, Bedford, Massachu- Chemicals and Reagents setts, USA). All reagents were of analytical grade. Potassium dihy- drogenphosphate (KH2PO4), phosphoric acid, sodium Solutions hydroxide, sodium acetate, and hydrochloric acid were All Dissolution media used in this study (water, M. purchased from Vetec (Rio de Janeiro, Rio de Janeiro, Bra- hydrochloric acid, pH acetate buffer, and pH zil). FNS reference substance (assigned purity ) was phosphate buffer) were degassed at 41 C in an ultrasonic acquired from USP (Rockville, Maryland, USA). Acetonitrile bath for 20 min prior to use. The M hydrochloric acid was of HPLC grade and was acquired from both Vetec (Rio solution was prepared by adding mL of hydrochloric de Janeiro, Rio de Janeiro, Brazil) and Burdick & Jackson acid to L of water. The pH sodium acetate buffer (Muskegon, Michigan, USA).

6 Reverse osmosis water was ( M) was prepared by adding g of sodium acetate obtained using a water purifier OS 10 LTH (Gehaka, S o trihydrate and mL of glacial acetic acid to L of Paulo, S o Paulo, Brazil) and was used to prepare dissolu- water. The pH potassium phosphate buffer ( M). tion media. HPLC grade water used in the mobile phase was prepared by adding g of potassium dihydro- was prepared with a Milli-Q system (Millipore, Bedford, genphosphate and mL of M sodium hydroxide Massachusetts, USA). to L of water. FNS capsules that contained 5 mg of the active compo- The stock standard solution of FNS at 100 g/mL was nent were used in this study and were supplied from three prepared in a 100 mL volumetric flask by dissolving an compounding pharmacies, codified as A, B, and C. In addi- accurately weighed amount ( mg) of FNS standard tion, a placebo mixture containing the same quantitative ( purity) in the mobile phase. Working standard so- composition as the capsules was obtained from the com- lutions were prepared immediately before use by diluting pounding pharmacies.

7 The placebo mixture contained the the corresponding stock solutions to appropriate concen- following inactive excipients: aerosil, sodium lauryl sulfate, tration levels using potassium phosphate buffer, sodium talc, starch, and lactose hydrous powder (Product A); talc, acetate buffer, hydrochloric acid, or purified water. starch, and lactose hydrous powder (Product B); and mag- Sample solutions were prepared by placing one nesium stearate, aerosil, sodium lauryl sulfate, talc, starch, capsule in each vessel (n = 6) containing the dissolu- and lactose hydrous powder (Product C). tion medium (500 mL) at a temperature of 37 C. The FNS reference drug product (Proscar tablets, lot Samples were collected at the end of the specified time 300060) was purchased from Merck Sharp & Dohme and filtered through quantitative VETEC filter paper. For (Whitehouse Station, New Jersey, USA). This product con- the HPLC analysis, standard and samples were filtered tained 5 mg of the active component and the following through a m PTFE membrane filter (Millipore, Bed- pharmaceutical grade excipients: cellulose, microcrystal- ford, Massachusetts, USA) prior to injection into the HPLC.

8 Line, docusate sodium, lactose monohydrate, magnesium system. stearate, pregelatinized maize starch, sodium starch glycolate type A, yellow iron oxide, hyprolose, indigo Chromatographic Conditions carmine aluminium lake, hypromellose, talc, and titanium The chromatographic separation was achieved at 30 C. dioxide. on a Lichrospher reversed-phase C8 (150 mm, 5 m). endcapped column (MetaChem Technologies Inc., Tor- Instrumentation rance, California, USA) using acetonitrile/water (70:30, v/v). Dissolution tests were performed in an Electrolab TDT as the mobile phase at a flow rate of mL/min. The mo- 08L multi bath (n = 8) Dissolution test system (Mumbai, bile phase was prepared daily, filtered through a m Maharashtra, India) equipped with Apparatus 1 (basket) membrane filter (Millipore, Bedford, Massachusetts, USA), and 2 (paddle) in accordance with USP General Chapter and degassed using the degasser of the chromatographic <711> (26). system prior to use.

9 The detector wavelength was set at The HPLC was a Shimadzu series LC 10A (Kyoto, Kyoto, 210 nm, and the injection volume was 20 L. Japan) consisting of LC 10 ADVP pump, CLASS-VP integration system software, DGU-14A degasser, 7725i Finasteride Solubility manual injector with a 20 L loop (Rheodyne, Rohnert The solubility of Finasteride was expressed in terms of Park, California, USA), SPD-10 AVP integrated UV detec- log D. The partition coefficient of an uncharged com- tor, LC-10 AVP low-pressure gradient valve, CTO-10 AVP pound in the aqueous and octanol phases is called log column oven, and SCL-10 AVP controller. P (for partition). When a given pH is used, the resulting 26 Dissolution Technologies | AUGUST 2013. partition coefficient is called log D (for distribution). In this temperature for 2 h and evaluated again. For each solu- work, theoretical values for Finasteride log D between pH tion, the results obtained after 2 h were compared with 1 and 13 were calculated using ACD Lab software (ACD/ the results obtained at time zero.)

10 An analytical response Structure Designer, version , Advanced Chemistry after 2 h between 98% and 102% of the response ob- Development, Toronto ON, Canada). tained at time zero is acceptable. Dissolution Test Optimization Selectivity Because there is no reference product in capsule form, For determination of selectivity, the placebo sample and the Dissolution experimental conditions were established capsule shell were transferred to separate vessels contain- with only one of the three products used in this work ing 500 mL of water at 37 C and stirred for 45 min at ( capsule C). Initially, water, M HCl, pH acetate buf- 100 rpm using the basket stirrer as the apparatus. Aliquots fer, and pH potassium phosphate buffer were tested were collected, and the interference of the placebo mix- as Dissolution media using a basket stirrer at a speed of 50 ture of each formulation was evaluated by HPLC. rpm. With water as the Dissolution medium, the influence of rotation speed of the basket stirrer on the FNS capsule Linearity release was checked at 50, 75, and 100 rpm.