Tropical Journal of Pharmaceutical Research Pharmacotherapy Group, Faculty of Pharmacy, University of Benin, Benin City, Nigeria ISSN: 1596-5996 EISSN: 1596-9827 Vol. 9, Num. 4, 2010, pp. 395-399

Tropical Journal of Pharmaceutical Research, Vol. 9, No. 4, July-August, 2010, pp. 395-399

Research Article

A comparative study of the pharmacokinetics of conventional and sustained-release tablet formulations of aceclofenac in healthy male subjects

Santanu Ghosh, BB Barik

University Department of Pharmaceutical Sciences, Utkal University, Bhubaneswar, Orissa-751004, India

Correspondence Address: Santanu Ghosh, University Department of Pharmaceutical Sciences, Utkal University, Bhubaneswar, Orissa-751004, India, santanu97@rediffmail.com

Date of Submission: 06-Nov-2009
Date of Acceptance: 11-Jul-2010

Code Number: pr10047

Abstract

Keywords: Pharmacokinetics; Bioequivalence; Sustained release aceclofenac formulation

Introduction

Aceclofenac is a relatively new phenylacetic acid derivative showing marked anti-inflammatory, anti-arthritic, analgesic and anti-rheumatic activities ^[1] . The drug demonstrates better gastric tolerance than other non steroid anti-inflammatory drugs (NSAIDs) such as indomethacin and diclofenac ^[2] . Its recommended dose is 100 mg twice a day orally in the form of tablets. After oral administration, it is rapidly absorbed and bioavailability is almost 100% ^[3] . Peak plasma concentrations are reached within 1.25 to 3 h following ingestion ^[3] . It is highly protein-bound (> 99.7 %) and penetrates into the synovial fluid, where the concentration reaches up to approximately 60 % of that in plasma ^[3] . The volume of distribution is approximately 30 L while mean plasma elimination half-life and clearance are 4.3 ± 0.3 h and 5 L/h, respectively ^[3] .

Aceclofenac is probably metabolized via Cytochrome P450 2C9 (CYP2C9, a protein encoded by the CYP2C9 gene in humans) to the main metabolite 4-hydroxyacefenac with negligible contribution to clinical activity ^[3] . Its adverse reactions, as with other NSAIDs taken by mouth, are indigestion, heartburn, nausea and diarrheoa ^[3] .

The objective of this study was to examine the in vivo bioequivalence of a test 200 mg aceclofenac sustained release formulation in relation to a commercial brand of 100 mg aceclofenac in male volunteers.

Experimental

Materials

The reference aceclofenac product used was an immediate release Zerodol® 100mg film-coated tablets, supplied (Ipca Laboratories, Mumbai, India). Aceclofenac was a gift from Mepro Pharmaceuticals Pvt. Ltd. Suren-dranagar, India. The excipients used in the production of the tablets were hydroxypropyl methylcellulose (HPMC) viscosity grade 4000 cps, (Methocel K4M, Colorcon Asia Pvt Ltd, Singapore) and lactose (DMV International, USA). Others were polyvinyl pyrollidone (PVP) K-30, (International Fine Chemicals Inc,, Canada), sodium propyl paraben (Salicylates and Chem Pvt Ltd, India), fumaric acid, magnesium stearate (Nitika Chemicals, India), talc (Udaipur Mineral Development Syndicate Pvt Ltd, India), colloidal silicon dioxide (Aerosil), isopropyl alcohol (Ranbaxy Fine Chemicals, India), methylene chloride (Chemplast Sanmar Ltd, India) titanium dioxide (Dupont Company Pvt Ltd, Singapore), PEG-6000 (Manali Petro Chemicals, India), castor oil (Sundarballi Oil Mill, India) and Ponceau 4 R supra (Roha Dye Chem, India). All other chemicals used were of analytical grade.

Preparation of aceclofenac sustained release tablets

The tablets were prepared by a wet granulation technique. The composition of the tablet formulations are given in [Table - 1]. Aceclofenac, Methocel K4M, lactose/maize starch, sodium propyl para benzoate and fumaric acid were screened through a 425 μm sieve and mixed manually in a bowl for 5 min. The blend was granulated with the aid of PVP K-30 and water. The mass was sieved through a 500 μm sieve and then dried in a hot air oven at 50 °C. Magnesium stearate, talc and colloidal silicon dioxide were then added to the dried granules, mixed for about 5 min in a polythene bag and compressed into tablets using a 12- station tablet compression machine (CIP Machineries, Ahmadabad, India) equipped with a 11 mm biconcave-faced punches. To mask the bitter taste of the aceclofenac, the tablets were coated in a laboratory coater (Model GAC- 250, Gansons Ltd, Mumbai, India) with HPMC 5cps dissolved in a mixture of isopropyl alcohol and methylene chloride; titanium dioxide and Ponceau 4 R supra (colouring agents) as well as polyethylene glycol (PEG) 6000 and castor oil (plasticizers) were also incorporated in the coating mixture prior to coating.

Physiochemical characterization of the tablets

Tablet weight variation was evaluated on ten randomly selected tablets with an electronic balance (Mettler Toledo, Mettler, Griefensee, Switzerland) while tablet hardness and friability were also determined for ten randomly selected tablets using a Monsanto tablet hardness tester (standard type) and a Campbell electronic friabilator for 4 min at 25 rpm, respectively. Tablet diameter was evaluated with a digital vernier caliper.

Subjects and ethical issues

This study was performed in accordance with United States Food and Drugs Administration (FDA) Good Clinical Practice guidelines. Volunteers enrolled for this study were appraised in detail about all aspects of the study in easy to understand language and terminologies. Before admission to the study each subject was informed of the nature and the risks of the study and a written informed consent was obtained from the volunteers. The study involved twenty four healthy, adult, non-smoking male volunteers (mean age: 32.25 ± 5.53 years; mean height: 165.25 ± 3.96 cm; and mean weight: 62.25 ± 3.96 kg) with no revealed medical abnormality. The experimental protocol was approved by the instituional Central Ethics Committee (ref no. CEC/05/018) and the study was conducted at the Drug Monitoring Research Institute (DMRI), Sion, Mumbai, India.

Study design

All the volunteers were housed at the study centre. They were randomly divided into 2 groups of 12 subjects each. After an overnight fast (10 h), each group received orally, with 250 ml of water, either a single dose of the test sustained-release formulation or the reference product in a randomized fashion, using a two-treatment, two-way crossover study design. A seven-day washout period was allowed between dosing schedules.

Sample collection and handling

Blood samples (2ml) were collected by the intravenous route using heparinized disposable syringes at the following times: 0, 0.5, 1.0, 1.5, 2, 3, 4, 5, 6, 8, 10, 12, 16, 18, 20 and 24 hours after drug administration. The blood samples were collected in vacutainers containing EDTA as anticoagulant and immediately centrifuged at 3000 rpm for 15 min. The separated plasma samples were stored at -20 ⁰ C until analysed.

Preparation of standard solutions

A stock solutions (1 mg/mL) of aceclofenac was prepared with methanol as the solvent. From the stock solution, standard solutions were prepared to contain 1, 2, 5, 10, 20, 30, 50 and 70 μg/mL of aceclofenac. A solution of ibuprofen (500 μg/mL) was prepared in a methanol/water mixture (80:20) and used as internal standard in the assay of aceclofenac.

Analysis of drug in plasma

To 100 μL of plasma, 25 μL of the internal standard and 200 μL of acetonitrile were added and mixed for a minute, and then made up to 1 ml with acetonitrile. The resulting solution was vortexed for 60 s and centrifuged at 10,000 rpm for 10 min. The supernatant layer was separated and analyzed for aceclofenac content using a sensitive high performance liquid chromatographic (HPLC) method with a Shimadzu Class VP series incorprating Class VP 6.12 version software, two pumps (LC-10AT VP), a variable wavelength programmable UV detector (SPD-10A VP), a system controller (SCL-10A VP) and an RP C-18 column (Hypersil BDS C18). The operating conditions and parameters include: mobile phase: methanol + 0.3% tri ethyl acetic acid (60:40 v/v, pH 7.0); flow rate: 1.0 mL/min; injection volume: 20 mL; temperature: 25 ^o C; run time: 25 min; detection wavelength: 275 nm; and internal standard - ibuprofen. The response factor was measured by the ratio of the peak area of drug to that of the internal standard for both standard and test samples. Blank plasma samples were analyzed prior to the analysis of the standard and test preparations. Preliminary studies had shown that the presence of plasma did not interfere with the analysis of the drugs. The peaks were well resolved and the retention times were 5 min (aceclofenac) and 10.5 min (ibuprofen).

Data analysis

Using the non-compartmental approach, plasma levels of aceclofenac were employed to compute their individual disposition kinetics, viz, C _max (maximum plasma concentration), T _max (time to reach maximum plasma concentration), AUC _0-t (area under plasma concentration-time curve), AUC _0-∞ (area under plasma concentration time curve, 0 to infinity), K _el (elimination rate constant) and t _1/2 (elimination half-life). Pharmacokinetic parameters were calculated with PK Solutions 2.0 ^TM Noncompartmental pharmacokinetic data analysis software.

Student′s t-test was employed to analyze the results using Graph Pad Instat Software, version 1.13. Differences below the probability level of 0.05 were considered statistically significant. The ratios of the mean bioavailability parameters (test : standard) were obtained and 90 % confidence interval was used to determine bioequivalence. Log (natural) transformation of C _max and AUC _0-∞ were performed prior to the statistical analysis. The equivalence criteria range was 80 to 125 % based on FDA guidelines. Calculations also included area under curve (AUC) from time t to ∞ (infinity) calculated with poly-exponential and trapezoidal methods.

Results

Physicochemical properties of the formulated tablets

Tablet thickness was in the range 3.6 - 3.9 mm; diameter, 11.0mm; and hardness, 5.0 - 8.0 g/cm ² . Tablet friability and coefficient of weight variation (for individual tablets) were 0.5 and 1.4 to 3.5 %, respectively. Drug content (99 - 100 %) was uniform. [Figure - 1]

Pharmacokinetic profiles of aceclofenac tablets

Administration of the reference product as a single dose produced C _max of 12301 ± 3000 ng/ml at a t _max of 1.29 ± 0.75 h while C _max for the test preparation was 11043 ± 3073 ng/ml at a t _max of 2.58± 1.22 h [Table - 2]. The bioavailability of the test preparation relative to that of the standard was 91.1 %. C _max , AUC _0-t and AUC _0-∞ values of the test preparation were 96.4 - 101.3 %, 100.2 - 101.9 % and 98.5 - 99.8 % of that of the reference, as shown in [Table - 3].

Discussion

Aceclofenac was available in plasma within half an hour after its oral administration. The t _max of the test aceclofenac was significantly different (p < 0.05) from that of the standard. Low t _max value for the reference drug (1.29 h) indicates rapid absorption while the higher t _max of the test drug (2.59 h) suggests slower absorption. This delayed absorption of test preparation is most likely due to the sustained release of the drug. On the other hand, the C _max of reference formulation was not significantly different from the test preparation. The half-life of the reference preparation was low which indicates rapid removal of the drug from plasma. This was also supported by the high elimination rate constant value. On the other hand, the test formulation exhibited higher half-life and low elimination rate constant values indicating slower drug disposition and prolonged effect. However, the AUC _0-∞ values for the two formulations were not significantly different. There was also no difference in the extent of absorption for both the test and reference products as indicated by the less than 10 % difference in relative bioavailability (91.1 versus 100 %) of the drug. This suggests that the aceclofenac contained in the test product was completely absorbed.

Conclusion

The test product showed sustained release characteristics unlike the reference. Overall, the pharmacokinetic profile of the former was either equivalent or superior to that of the reference. Thus, the test aceclofenac preparation can be further developed to achieve a suitable sustained release product.

Acknowledgment

The authors wish to acknowledge M/s Mepro Pharmaceuticals Pvt Ltd, Surendranagar Gujarat, India, for providing the reference standard and pure aceclofenac used in the study. ^[6]

References

Copyright 2010 - Tropical Journal of Pharmaceutical Research

The following images related to this document are available:

Photo images