Vol - 4, Issue - 1, Jan 2013 ISSN: Ghinaiya et al PHARMA SCIENCE MONITOR

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1 PHARMA SCIENCE MONITOR AN INTERNATIONAL JOURNAL OF PHARMACEUTICAL SCIENCES FORMULATION AND EVALUATION OF TRANSDERMAL PATCH OF AN ANTIHYPERTENSIVE DRUG Mitali Ghinaiya* N. R. Vekaria Institute of Pharmacy, C.L. College Campus, Bilkha road, Junagadh , Gujarat, India ABSTRACT Valsartan is a new potent, highly selective and orally active antihypertensive drug because of its selectivity and specificity on the smooth vascular cells. The pharmacokinetic parameters make valsartan a suitable candidate for transdermal delivery. The purpose of the study was to select a suitable formulation for the development of transdermal drug-delivery system (TDDS) of valsartan and to determine the effect of plasticizers and different polymeric grades of hydroxy propyl methyl cellulose (K4M, K15M, K100M) on drug release. The matrix type TDDS of valsartan were prepared by solvent casting technique. Six formulations were composed of hydrophilic polymers like sodium alginate and different polymeric grades of hydroxy propyl methyl cellulose (K4M, K15M, and K100M) and different plasticizers like PEG-400 and PG. The prepared TDDS were evaluated for physicochemical characteristics, in-vitro drug release, ex-vivo permeation and skin irritation study. The ex-vivo permeation study was carried out using rat skin for optimized formulation. All the formulations exhibited satisfactory physicochemical characteristics. Cumulative percentage of the drug released in 12 hrs from the six formulations were %, %, %, 99.8 %, % and 89.4 % respectively. Ex-vivo drug release values for the cumulative amount of the drug permeated across the rat skin from optimized formulation was %. By fitting the data into zero order, first order, Higuchi model and Korsemeyer peppas, it was concluded that drug release from matrix films followed zero order release model and the mechanism of the drug release was due to swelling of hydrophilic polymers. The patches were seemingly free of potentially hazardous skin irritation. In conclusion, the present data confirm the feasibility of developing TDDS of valsartan for potential therapeutic use. Keywords: Transdermal drug delivery, Valsartan, Hydrophilic polymers. INTRODUCTION Currently, transdermal drug delivery is one of the most promising methods for drug application. Increasing numbers of drugs are being added to the list of therapeutic agents IC Value

2 that can be delivered to the systemic circulation via skin. The transdermal route offers several advantages over conventional dosage forms such as tablets and injections, including avoidance of first-pass metabolism by the liver, minimization of pain, reduction of side effects, extended duration of activity, reduction in the fluctuations of drug concentrations in the blood, and possible sustained drug release 1. Valsartan is a non peptide, orally active and specific angiotensin II antagonist acting on the AT1 receptor subtype. The Valsartan heart failure trial demonstrated that the use of Valsartan was associated with reduced rate of heart failure related hospitalizations and mortality as well as shorter duration of hospitalization 2. Valsartan, N- valeryl- N[[2- (1Htetrazol- 5- yl)biphenyl- 4- yl] methyl] valine has an empirical formula of C 24 H 29 N 5 O 3 and a molecular weight of g/mol 3,4,5. It was synthesized in 10 steps and patented in Valsartan is available as a white, microcrystalline powder. Valsartan is considered as a class II compound, i.e. water-insoluble and highly permeable 6. Valsartan is poorly soluble and aqueous solubility is reported to be less than 1 mg/ml. The drug is rapidly absorbed following oral administration, with a bioavailability of about 23%. Peak plasma concentrations of Valsartan occur 2 to 4 h after an oral dose and 94% to 97% of the drug is bound to plasma proteins 5. The aim of the study is to achieve the objective of systemic medication through topical application and release of drug via skin by developing transdermal drug delivery system. To obtain a controlled, predictable and reproducible absorption and release in to blood stream, more uniform plasma levels, improved bioavailability, reduced side effects, painless and simple application are some of the potential need to formulate the transdermal drug delivery system arises. MATERIALS AND METHODS Materials Valsartan was received as gift sample from Torrent research centre, Ahmedabad, India. Na alginate, Hydroxy propyl methyl cellulose (K4M, K15M and K100M), Polyethylene IC Value

3 glycol 400 and Propylene glycol were received from Yarrow chem. Ltd, Mumbai. All the other solvents and chemicals were of Laboratory Reagent grade. Determination of solubility of Valsartan 7, 8 The Valsartan has very low aqueous solubility. The solubility was determined in distilled water and phosphate buffer ph 7.4. Here, excess drug (50 mg) was added to 50 ml distilled water/ phosphate buffer ph 7.4 in a 50 ml volumetric flask and the mixture was shaken and kept for 48 h at room temperature. The sampling was done on 24th & 48th hour and filtered immediately using a whatman filter paper. The filtered sample was diluted suitably and assayed at 250 nm for valsartan. The solubility experiments were replicated for three times (n=3). Determination of partition coefficient 8, 9 The partition coefficient study was performed using n-octanol as the oil phase and phosphate buffer ph 7.4 as the aqueous phase. The two phases were mixed in equal quantities by adding 20 mg of drug in a separating funnel and were saturated with each other at room temperature for 24 hrs. The saturated phases were separated by centrifugation. The two phases were separated and were then analyzed for respective drug contents. The partition coefficient of drug (Ko/w) was calculated using the following formula: Preparation of Transdermal Patches: The valsartan patches were formulated using solvent casting method, by dissolving weighed quantity of drug in required volume of methanol in a beaker. The selected concentrations of polymers were dissolved in 10 ml of distilled water in another beaker. To this beaker, add the methanol solution containing drug. Keep the beaker on IC Value

4 thermostatically controlled magnetic stirrer which is maintained at 37±0.5ºC. The required quantity of plasticizer is added drop wise to the beaker while stirring is continued until the drug is dispersed with polymer. The solution was poured into petridish; an inverted funnel was placed over the petridish to prevent fast evaporation of the solvent and the films were allowed to dry overnight at room temperature. Then the Patches were cut into 2 2 cm 2 and packed in an aluminum foil and stored in desiccators for further use. Table 1: Formulation table of Valsartan Patches Ingredients F1 F2 F3 F4 F5 F6 Valsartan (mg) HPMC K4M (mg) HPMC K15M (mg) HPMC K100M (mg) Na alginate (mg) PEG-400 (%) PG (%) Methanol (ml) Water(ml) Note: Each patch (2 2 cm 2 ) contained 20 mg of Valsartan. PEG-400 and PG (30% w/w of total dry polymer), incorporated as plasticizers. EVALUATION OF TRANSDERMAL PATCHES 1. Physical appearance 10 All the prepared patches were visually inspected for color, clarity, flexibility and smoothness. 2. Patch thickness 11 IC Value

5 The thickness of the patch was measured at three different points using an aerospace micrometer and average thickness was found out. 3. Weight uniformity 10 For each formulation, the patches were cut from different positions and were weighed individually and the average weight was calculated. 4. Folding endurance 12 Folding endurance of patches was determined by repeatedly folding a small strip of film (2 cm x 2 cm) at the same place till it broke. The number of times, the patch could be folded at the same place without breaking gave the value of folding endurance. 5. Moisture content 13 The patches were weighed and kept in a desiccator containing calcium chloride at room temperature for 24 hr. The final weight of patch was noted. The percentage of moisture content was calculated as a difference between initial and final weight with respect to final weight. 6. Tensile strength 14 Tensile strength of the patch was determined with JAMCO tensiometer (Mfg by PONCO MACHINE TOOLS, Ahmedabad). The sensitivity of the machine was 1 g. It consisted of two load cell grips. The lower one was fixed and upper one was movable. The test film of size (2.5 1 cm 2 ) was fixed between these cell grips and force was gradually applied till the film broke. The tensile strength of the film was taken directly from the dial reading in g. Tensile strength is expressed as follows: 7. Drug Content cm 2 area of the patches was cut and each dissolved in minor quantity of methanol, till it dissolved. The volume was made up to 10 ml with phosphate buffer ph ml IC Value

6 was then withdrawn from this solution and diluted to 10 ml (dilution factor: 100). The absorbance was measured at 250 nm. From the absorbance and the dilution factor, the drug content in the patch was calculated. Average of triplicate readings was calculated. 10, 11, In-vitro diffusion study In vitro diffusion study was performed by using a modified Franz diffusion cell with a receptor compartment capacity of 200 ml. The dialysis membrane was mounted between the donor and receptor compartment of the diffusion cell. The formulated patches were cut into size of 2 2 cm 2 and placed over the drug release membrane and the receptor compartment of the diffusion cell was filled with phosphate buffer ph 7.4. The whole assembly was fixed on a magnetic stirrer, and the solution in the receptor compartment was constantly and continuously stirred using magnetic beads at 50 rpm; the temperature was maintained at 37 ± 0.5 C. The samples of 5 ml were withdrawn at time interval of 1 hr upto 12 hrs and analyzed for drug content spectrophotometrically at 250 nm against blank. The receptor phase was replenished with an equal volume of phosphate buffer ph 7.4 at each time of sample withdrawal. The cumulative amounts of drug permeated were plotted against time. 9. Ex-vivo skin permeation studies 11 Preparation of rat skin Male rats weighing gm, free from any visible sign of disease were selected. Using a depilatory preparation the hairs of the male rat was cutting by scissor. After cleaning the skin with phosphate buffer ph 7.4, animal was sacrificed by excessive ether inhalation. An incision was made on the flank of the animal and the skin was separated. The prepared skin was washed with phosphate buffer ph 7.4 and used. Ex-vivo skin permeation study The prepared skin was tied on the donor compartment with transdermal patch. While placing the patch, the donor compartment contains patch on stratum corneum side of skin and dermis side was facing receptor compartment. Receptor compartment contains IC Value

7 ml of phosphate buffer ph 7.4 and every one hour 5 ml of sample was taken and replaced the same with receptor fluid. After 12 hours sampling absorbance taken at 250 nm against blank of phosphate buffer ph 7.4 by UV spectrophotometer. 10. Skin irritation study 16 A primary skin irritation test was performed since skin is a vital organ through which drug is transported. The test was carried out on healthy rabbits weighing 1.3 to 1.5 kg. Drug free polymeric film of diameter 2 2 cm 2 was used as control. The dorsal surface of rabbits was cleared well and the hair was removed by using a depilatory preparation. The skin was cleared with rectified spirit. The patches were applied to the shaved skin of rabbits and secured using adhesive tape USP (Leucoplast TM). On one side of the back control patch (without any drug) and on the other side an experimental patch were secured. A 0.8%v/v aqueous solution of formaldehyde was applied as a standard irritant and its effect was compared with test on same rabbit. The animals were observed for any irritation for a period of 7 days. All the experimental protocols involving laboratory animals were approved by the IAEC (Research Proposal No. : - NRV-04/2012) 11. Release kinetic models 20 In order to understand the mechanism and kinetics of drug release, the drug release data of the In- Vitro diffusion study were analyzed with various kinetic models like zero order, first order, Higuchi s, Peppa s model and co-efficient correlation values were calculated for the linear curves by regression analysis of the above plots. 17, Permeation Data Analysis The flux (μg cm -2 hr -1 ) (Jss) of Valsartan was calculated from the slope of the plot of the cumulative amount of Valsartan permeated per cm 2 of skin at steady state against the time using linear regression analysis: Jss = (dq/dt)ss 1/A Where, (dq/dt)ss = steady state slope A = effective diffusion area IC Value

8 The steady state permeability coefficient (Kp) of the drug through rat skin was calculated by using the following equation: Kp = Jss / C Where, C = the concentration of Valsartan in the patch. The penetration enhancing effect of penetration enhancer was calculated in terms of enhancement ratio (ER), and was calculated by using the following equation: 16, Accelerated stability study The optimized patch was subjected to stability study to evaluate any change in the performance when exposed to accelerated conditions of environment during storage, handling transport and use. The patch was packed in the aluminum foil and was kept in stability chamber at 40 C and 75% RH for a period of one month. The patch sample with an area of 4 cm 2 was cut and it was analyzed for physical parameters and drug content at the end of a month. The average of triplicate readings was taken. RESULTS AND DISCUSSION The solubility of Valsartan was determined and found very less as mg/ml in distilled water and mg/ml in phosphate buffer ph 7.4 after 48 hrs. n-octanol (oil phase) and phosphate buffer ph 7.4 (aqueous phase) were considered to be the standard system to determine drug partition coefficient. The partition coefficient value was found to be ±0.0004, which is nearer to the reported value (0.033). The IR spectrum of Valsartan (Figure 5.3) sample revealed presence of major functional groups. The characteristic functional groups of the pure valsartan and physical mixtures of valsartan and polymers showed the peaks at the following wave number region: C-H stretching (Alkane): 2970 cm -1, C=O stretching: 1725 cm -1 ; N-H bending (Aromatic secondary amine): 1600 cm -1, 1510 cm -1 ; C-N stretching (Aromatic tertiary amine): IC Value

9 cm -1, 1100 cm -1 ; Aliphatic tertiary amine: 1410 cm -1 ; Disubstituted benzene: 750 cm -1. There was no appearance of any characteristics peaks. This shows that there was no chemical interaction between the drug and the polymers used.the presence of peaks at the expected range confirmed that the materials taken for the study are genuine and there were no possible interactions occurred. Hence the sample is considered to be authentic. The IR spectra showed no incompatibility between the polymer and Valsartan drug. Figure 1: IR spectra of pure drug Figure 2: IR spectra of Drug + HPMC K4M IC Value

10 Figure 3: IR spectra of Drug + HPMC K15M Figure 4: IR spectra of Drug + HPMC K100M Figure 5: IR spectra of Drug + Sodium alginate IC Value

11 Figure 6: IR spectra of mixture of drug and polymer The formulated valsartan transdermal patches were evaluated for thickness, weight uniformity, folding endurance, moisture content, tensile strength and drug content were observed in Table 2. All the prepared patches were observed physically and they were found to be transparent, smooth, uniform and flexible. The thickness of the patches varied from to mm. Low standard deviation values in the patch thickness measurements ensured uniformity of patches prepared by solvent casting technique. The weight uniformity was to be in the range of to gm, which indicates that different batches patch weights were relatively similar. The folding endurance was found to be in the range of 252 to 285. This data revealed that the patches did not break and had good mechanical strength along with flexibility and maintained their integrity with general skin folding when applied. The moisture content was found to be in the range 1.72 to 2.62%. The low moisture content in the formulations resulted in stability of patches and not giving a completely dried and brittle film. The tensile strength was found to be in the range of to g/cm 2. The tensile strength measures the ability of a patch to withstand IC Value

12 rupture. The drug content was in the range of to %, which revealed that the drug content was almost uniform in all the patches. Formulation code Table 2: Physico-chemical characterization of Valsartan transdermal patches Patch thickness (mm) Weight uniformity (gm) Folding endurance Moisture content (%) Tensile strength (g/cm 2 ) Drug content (%) F ± ± ± ± ± ±0.382 F ± ± ± ± ± ±0.878 F ± ± ± ± ± ±1.25 F ± ± ± ± ± ±0.382 F ± ± ± ± ± ±0.25 F ± ± ± ± ± ±0.144 The in-vitro drug diffusion for six formulations is given in the Table 3. Here, F4 formulation showed maximum drug release. Time (hrs) Table 3: In-vitro drug release data of Valsartan Transdermal patches % Cumulative drug release F1 F2 F3 F4 F5 F ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± IC Value

13 Figure 7: In-vitro drug release study of Valsartan Transdermal patches The ex-vivo drug permeation study was carried out for optimized formulation using rat skin as a semipermeable membrane and drug release data is given in the Table 4. Table 4: Comparison of In-vitro and Ex-vivo drug release data of optimized batch Time (hrs) In-vitro % cumulative drug release Ex-vivo % cumulative drug release IC Value

14 Figure 8: Comparison of In-vitro and Ex-vivo drug release data of optimized batch A primary skin irritation test of patch F4 on rabbit was studied. No signs of erythema, oedema or ulceration were observed on the skin of albino rabbits after 7 days. To know the mechanism of drug release, the in-vitro release data were fitted to models representing Zero order, First order, Higuchi and Korsemeyer Peppas model. It was found that the release of Valsartan from the transdermal patch followed zero order kinetics. The coefficient of determination (R 2 ) was found to be much closer to 1 for zero order equation. This suggests that the drug permeation from transdermal patches, possibly owing to swelling of hydrophilic polymer. As per Korsemeyer-Peppas model, Formulation F1, F2, F4 and F5 follows anomalous type drug release mechanism, i.e. nonfickian diffusion. The release kinetic parameters are shown in Table 5. IC Value

15 Formulation code Table 5: Kinetic release parameters for Valsartan transdermal patches Kinetics Modeling Zero order First order Higuchi Korsemeyer- Peppas k 0 R 2 k 1 R 2 K R 2 n R 2 Model F Anomalous F Anomalous F Super case- II transport F Anomalous F Anomalous F Super case- II transport The flux value for formulation F4 was found to be maximum, which is 2.632±0.023 μg cm -2 hr -1 and permeability coefficient was 1.32± cm hr -1. The results obtained for permeation data is given in the Table 6. Sr. No Table 6: Permeation data analysis of Valsartan Transdermal patches Formulation code Flux (J) (μg cm -2 hr -1 ) Diffusion coefficient (cm 2 /h) Permeability co efficient (KP) (cm hr ) Enhancement ratio (ER) 1 F ± ± ± F ± ± ± F ± ± ± F ± ± ± ± F ± ± ± ± F ± ± ± ± IC Value

16 In the present work stability study was carried out for selected formulation F4 for one month. The samples were evaluated for physicochemical parameters like thickness, folding endurance, tensile strength, moisture content, drug content and drug release. Results are the mean of triplicate observations ± SD. From comparison results, it was concluded that the release of drug after stability period was nearly same as those of patch, before the stability period. Hence, stability study indicates that the formulation is quite stable at accelerated conditions. The results after stability period are given in Table 7. Table 7: Accelerated stability study for Optimized formulation Test Parameters Result before stability period Result after stability period Patch thickness (mm) 0.243± ±0.010 Weight uniformity (gm) 0.097± ± Folding endurance 267± ±5.86 Moisture content (%) 1.72± ±0.59 Tensile strength (gm/cm 2 ) ± ±1.72 % elongation (% cm -2 ) 62.67± ±1.51 Drug content (%) 97.92± ±0.63 Table 8: In-vitro drug release data after stability period for optimized batch Time (hrs) In-vitro % CDR before stability period In-vitro % CDR after stability period IC Value

17 Figure 9: In-vitro drug release data after stability period for optimized batch CONCLUSION The transdermal patch formulation was found to be efficacious, safe, stable and non irritant to skin. The formulation F4 (HPMC K4M and sodium alginate using propylene glycol as a plasticizer) was optimized and it showed release in concentration independent manner. The above formulation gave a maximum drug diffusion of 99.8 % over a period of 12 hours. The drug release kinetics of all fabricated patches follows zero order kinetics and the mechanism of drug release from all formulations were swelling type. Further, exvivo studies have to be performed to correlate with in-vitro release data for the development of suitable controlled release patches for Valsartan. As an extension of this work pharmacokinetic studies, in-vivo studies on higher animals and controlled clinical studies on human beings will be carried out in future. REFERENCES 1. Prausnitz MR, Mitragotri S, Langer R. Current status and future potential of transdermal drug delivery. Nature Reviews, Drug Discovery 2004, 3: IC Value

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19 12. Rathore RPS, Chauhan CS, Naruka PS, Tanwar YS, Chauhan LS. Transdermal formulation of terbutaline sulphate. Pharmacy online Gannu R, Vishnu YV, Kishan V, Rao YM. Development of nitrendipine transdermal patches: In vitro and Ex vivo characterization. Curr Drug Deliv 2007, 4: Kavitha K, Kumar DP. Development of transdermal patches of nicardipine hydrochloride: An attempt to improve bioavailability. Int J Res Pharma Biomed Sci 2011; 2(1): Patel HJ, Patel JS, Desai BG, Patel KD. Design and evaluation of amlodipine basilate transdermal patches containing film former. Int J Pharma Res Dev 2009; 7; Dey S, Malgope A. Preparation of carvedilol transdermal patch and the effect of propylene glycol on permeation. Int J Pharm Pharma Sci 2010; 2(1); Mamatha T, Rao VJ, Mukkanti K, Gannu R. Development of matrix type transdermal patches of lercanidipine hydrochloride: physicochemical and in-vitro characterization. J Pharm Sci 2010; 18(1); Patel RP, Patel G, Baria A. Formulation and evaluation of transdermal patch of aceclofenac. Int J Drug Deli 2009; 1: Gavali P, Gaikwad A, Radhika PR, Sivakumar T. Design and development of hydroxy propylmethylcellulose (HPMC) based polymeric film of enalapril maleate. Int J Pharm Tech Res 2010; 2(1): Latha S, Selvamani P, Thirunavukkarasu C, Kadambavadani R. Formulation development and comparison in evaluation of transdermal drug delivery system for anti-emetic therapy. Int J Res Pharma Biomed Sci 2011; 2(2): For Correspondence: Mitali Ghinaiya mitali.ghinaiya@gmail.com IC Value