Formulation and Evaluation of Pulsatile Drug Delivery System of Montelukast Sodium

INTRODUCTION

Oral control drug delivery offers a number of advantages over conventional immediate release system. These systems are designed to deliver the drug at controlled and predetermined rate thus maintaining their therapeutic concentration in systemic circulation for prolonged periods.¹

Diseases like bronchial asthma, angina pectoris, rheumatic arthritis, ulcer and hypertension required time dependence drug delivery system. Such a condition demands pulsatile i.e. sudden burst drug release rather than maintaining constant plasma drug level.² A pulsatile drug delivery system is characterized by a lag time that is an interval of no drug release followed by rapid and complete drug release.²

The principle of time controlled drug delivery systems is that the release of the drug happens according to a predetermined rate so to achieve maximum therapeutic and minimum toxic effect.³ Chronotherapeutics delivery system have been developed to provide the best treatment regimens which revolve around the objective of assuring maximum concentration of the drug at the time of attack.⁴

Nocturnal asthma is defined as a variable nighttime exacerbation of the underlying asthma condition associated with increase in symptoms and need for medication, increased airway responsiveness and worsening of lung function. Approximately two-thirds of asthmatics suffer from night-time symptoms. Lung function is usually highest at 4 pm and lowest at 4 am. The mechanisms of nocturnal asthma are intimately related to circadian rhythms which can be treated by chronotherapy3.The chronopharmacotherapy for nocturnal asthma has been recommended to ensure the maximum release of the drug during the asthma attack. A pulsatile drug delivery system that can be administered at night (before sleep) nut release drug in early morning would be promising chronopharmaceutic system.⁵

The present work comprises of a core tablet, containing model drug Montelukast sodium and different concentrations of super disintegrants with an erodible outer coating of polymer so that immediate pulse of drug release can be achieved. The dip coating of the core tablet which increases the lag time of tablet by increasing the coating levels of the polymers i.e. Eudragit S100 and ethyl cellulose. The intention was to maintain a lag time of 3- 4 h, as the symptoms of nocturnal asthma are experienced in the early morning hours 2 am to 4 am. The pH sensitive polymer Eudragit S100 and ethyl cellulose are soluble in intestinal pH which would lead to sudden burst of tablet. The incorporation of drug as immediate release formulation in core is proposed to provide the drug to patient at right time of asthmatic attack.⁶

The model drug used in present work is Montelukast sodium which is leukotriene receptor antagonist used as anti-inflammatory medications in the management and chronic treatment of asthma and exercise-induced bronchospasm. Its chemical name is 2-[1-({[(1R)-1-{3-[(E)-2- (7-chloroquinolin-2-yl) ethenyl] phenyl}-3- [2(2hydroxypropan-yl) phenyl] propyl] sulfanyl} methyl) cyclopropyl] acetic acid with molecular formula C₃₅H₃₅ClNNaO₃ S and molecular weight 608.18 g/mol. The bioavailability of Montelukast sodium is 63%, protein binding is 99% and its half life is 2.7-5.5 hours. Montelukast sodium inhibits bronchoconstriction due to antigen challenge. Montelukast is a selective leukotriene receptor antagonist of the cysteinyl leukotriene CysLT₁ receptor. The cysteinyl leukotriene bind to cysteinyl leukotriene receptors (CysLT) found in the human airway. Binding of cysteinyl leukotriene to leukotriene receptors has been correlated with the pathophysiology of asthma, including airway edema, smooth muscle contraction and altered cellular activity associated with the inflammatory process, factors that contribute to the signs and symptoms of asthma.⁷

The pulsatile dosage form taken at bed time with a programmed start of drug release early in morning hours which can prevent a sharp increase in the incidence of asthmatic attacks during the early morning hours (nocturnal asthma), a time when the risk of asthmatic attacks is the greatest.³

MATERIALS AND METHODS:

Materials

The drug Montelukast sodium is obtained as a gift sample from Glenmark pharmaceuticals ltd, Goa. Microcrystalline cellulose, Sodium starch glycolate and Croscarmellose sodium was obtained from Remedy labs, Ahmedabad. Crospovidone was obtained from Param pharma, Mumbai. Eudragit S100 as gift sample from Evonik India Pvt Ltd, Mumbai. Ethyl cellulose was obtained from Loba chemie, Mumbai. All the other chemicals were of analytical grade.

Preformulation studies:

Identification of pure drug⁸ :

The received sample of API was subjected to determination of its nature and viewed visually for the determination of its color and then the results were compared with the official books. The identification of the pure drug was done by IR spectrophotometer.

Melting point⁹ : Melting point of the drug was done in Theil’s melting point apparatus and the temperature at which the drug melted was noted down.

Solubility studies¹⁰: The solubility test of the drug was done in ethanol, water, NaOH, chloroform, methanol, pH 1.2 & pH 6.8, etc

Calibration curve for Montelukast sodium in 0.1 N HCl

Accurately weighed 100 mg of drug was dissolved in 0.1N HCl in 100 ml volumetric flask and volume was made up with 0.1N HCl to get a concentration of 1000 µg/ml. Then from stock I, 1ml was diluted to 10 ml to get 100µg/ml.

From the above stock solution, various dilutions were prepared to get the concentrations in a range of 10-100 µg/ml. The working standard was scanned for λmax using UV visible spectrophotometer.

Calibration curve for Montelukast sodium in pH 6.8 Phosphate Buffer 

Accurately weighed 100 mg of drug was dissolved in pH 6.8 in 100 ml volumetric flask and volume was made up with buffer to get a concentration of 1000 µg/ml. Then from stock I, 1ml was diluted to 10 ml to get 100 µg/ml.

From the above stock solution, various dilutions were prepared to get the concentrations in a range of 10-100 µg/ml. The working standard was scanned for λmax using UV visible spectrophotometer.¹¹

FTIR Analysis

FTIR analysis was carried out to find out the compatibility between the drug and excipients such as Croscarmellose sodium, Crospovidone, Sodium starch glycolate, Ethyl cellulose (EC), Eudragit S100, etc. All the polymers used in the formulations were mixed with the drug separately in equal ratios for FTIR studies. KBR pellets were prepared gently by mixing the 1:3 ratio of sample and potassium bromide. Then these pellets were kept in FT-IR spectrophotometer with keeping the range 400-4000cm^-1. The characteristic peaks were recorded.¹¹

FORMULATION OF MONTELUKAST SODIUM PULSATILE RELEASE TABLETS.

The pulsatile tablets prepared by dip coating method consisted of two different parts: a core tablet, containing the drug, microcrystalline cellulose, lactose and superdisintegrants with different concentrations. The nine core tablet formulations were prepared and evaluated. The two optimized core tablet formulations were selected for dip coating. The dip coating of core tablet is done by ethyl cellulose and Eudragit S100 with different coating levels.

The effect of formulation composition on the barrier layer comprising both polymers, excipients on the lag time of drug release was investigated. The compression coated tablets were evaluated for weight variation test, thickness, hardness, friability, lag time and dissolution study. Each tablet contained 10 mg of Montelukast sodium.

FORMULATION OF CORE TABLET:

The following ingredients were mixed uniformly, then the precompressional parameters were done and the powder samples were compressed.

FORMULATION OF COATED TABLET:

The core tablets were being coated with ethyl cellulose and Eudragit S100 with different coating level.

Procedure: The optimized core tablets were coated with different polymer with different coating levels i.e. D1-D4 The coating solution was prepared with mixing the polymers with isopropyl alcohol and acetone.12 Then the tablets were coated by dip coating method. The dip coating method was modified by dipping the tablet by help of mesh and drying it immediately. Then the tablets were kept in hot air oven for 24hrs. The coated tablet with C1, C2, C3 and C4 consisted of the F6 core tablet that was coated with D1, D2, D3 and D4 respectively. While the C5, C6, C7 and C8 consisted of the core tablet F9 coated with D1, D2, D3 and D4 respectively.

EVALUATION:

Precompressional studies:

Bulk density¹²:

The accurately weighed amount of 50 g of the powder sample was transferred into 100 ml of measuring cylinder and then the initial volume was noted. Then bulk density was calculated with ratio of the weight of the powder to the volume occupied.

Tapped density¹²: The accurately weighed powder was filled in the measuring cylinder and then the measuring cylinder was tapped as per pharmacopoeia guidelines until constant volume was obtained. The tapped density was measured by dividing weight by volume.

Carr’s index⁹ : Tapped density (ρt) and bulk density (ρb) of powder material was used to measure compressibility of a powder material. Equation of determining Carr’s index is,

Carr’s index (%) = [(TD-BD)] / TD x 100

TD= Tapped density

BD=Bulk density

Hausner’s ratio³ : It is the ratio of bulk volume to tapped volume or tapped density to bulk density. Tapped density (ρt) and bulk density (ρb) of powder material was used to measure Hausner’s Ratio.

Angle of repose¹³: The angle of repose was determined by the funnel method. The powder was filled in the funnel by closing one end and then the funnel was placed at a height such that the tip of the funnel just touches the apex of the heap of granules. Then it is allowed to flow at once and the pile of the powder formed was being calculated with its diameter and its height.

Post compression parameters of the core tablet and coated tablet:

Weight variation¹⁴: The weight of the tablet being made was routinely determined to ensure that a tablet contains the proper amount of drug. The USP weight variation test is done by weighing 20 tablets individually of each formulation, calculating the average weight and comparing the individual weights to the average. The USP specification is that not more than two tablets should be outside the percentage limit.

Hardness³ : The hardness of each formulation tablet was checked by using Monsanto hardness tester. The hardness of five tablets in each batch was measured and the average hardness was calculated in terms of kg/cm.²

Friability¹⁴: Twenty tablets were weighed, the initial weight of the tablets of all formulations were noted and placed in Roche friabilator and rotated at the speed of 25 rpm for 100 revolutions. Then tablets were removed from the friabilator, dusted off the fines, were weighed and the weight was recorded.

Tablet thickness¹⁵: Thickness of tablet of all the formulations was measured using vernier caliper by placing the tablet in it. The thickness was determined by checking the thickness of 5 tablets of each formulation.

Disintegration time for core tabelt¹⁶: Tablet disintegration is an important step in drug absorption. The test for disintegration was carried out in Electrolab disintegration test apparatus. It consists of 6 glass tubes which are 3 inches long, open at the top, and held against a 10 mesh screen, at the bottom end of the basket rack assembly. To test the disintegration time of tablets, one tablet of each formulation was placed in each tube and the basket rack was positioned in a 1 litre beaker containing pH 6.8 buffer solution at 37 °C ± 1 °C such that the tablet remains 2.5 cm below the surface of the liquid. The time taken for the complete disintegration of the tablets was noted.

Disintegration time for coated tablet:

To test the disintegration time of tablets, one tablet of each formulation was placed in each tube and the basket rack was positioned in a 1 litre beaker containing pH 1.2 Buffer solution at 37 °C ± 1 °C such that the tablet remains 2.5 cm below the surface of the liquid. The time taken for the complete disintegration of the tablets was noted. Then the disintegration of the tablet was done in the pH 6.8 and the time at which the tablet disintegrates was noted.

Wetting time¹⁷: Wetting time of dosage form is related to the contact angle. 3 tablets were taken for determining the wetting time. A piece of tissue paper was folded twice and placed in a small petridish containing 6 ml of water. Tablet was kept on the paper and the time for complete wetting was measured.

Drug content for core tablet and coated tablet¹⁸:

The tablets were tested for their drug content uniformity. 10 tablets were triturated and then 1 g of sample was accurately weighed which is equivalent to 100 mg of drug was dissolved in 100 ml of pH 6.8. Then solution was shaken thoroughly and was kept for sonication for 10 m. The undissolved matter was removed by filtration through whatman filter paper. Then 2 ml was taken from the stock I and was diluted to 10 ml for maintaining the concentration within the beer’s range. The absorbance of the diluted solutions was measured at 285 nm.

In-vitro Dissolution studies for core tablet19:

Dissolution testing of pulsatile core tablet was done with the paddle method at 50 rpm at 37±0.5 °C in 900 ml of pH 6.8 buffer. The samples were withdrawn at regular intervals. Fresh buffer was replaced and the sample was analyzed by UV spectrophotometer at 285nm.

In-vitro Dissolution studies for coated tablet¹⁹ :

Dissolution testing of pulsatile delivery system was done with the paddle method at 50 rpm at 37±0.5 °C in different buffers for different periods of time to simulate the GI tract pH and transit time. The dissolution of the tablet was first performed in pH 1.2 buffer for 2 hours and then in pH 6.8 phosphate buffer for remaining hours in dissolution test apparatus. The samples were withdrawn at regular intervals and analyzed by UV spectrophotometer at 285 nm.

Stability studies²⁰: Stability studies of the optimized formulations of coated Montelukast sodium tablets were carried out to determine the effect of formulation additives on the stability of the drug and also to determine the physical stability of the formulation according to ICH guide lines. The studies were carried out at 40ºC/75% RH for 30 days by storing the samples in accelerated condition.

RESULTS AND DISCUSSION:

Preformulation studies

Organoleptic properties

The received sample of the drug was found to be off whitish in colour and amorphous in nature.

IR Spectroscopy of the drug.

The peak of the drug sample obtained was similar to the theoretical frequencies referred in the pharmacopoeia. The IR frequencies gave CH stretching with 2954 cm^-1, NH Rocking with 874.75cm^-1, C-N amines with 1326.12cm^-1. These frequencies matched the characteristic frequencies in the pharmacopoeia. The obtained spectrum is mentioned in Figure 1 and the frequencies are mentioned in Table 3.

Melting point:

Melting point of Montelukast sodium was determined by capillary method. Melting point was found to be 136 ˚C and is depicted in Table 4.

Solubility studies:

The drug was soluble in ethanol, methanol, 0.5% SLS, pH 1.2, pH 6.8 and slightly insoluble in water.

UV Spectroscopy:

λmax of Montelukast sodium was found to be 386 nm in pH 1.2 and 285nm in pH 6.8 as these showed maximum absorbance in the wavelength. Different concentrations were analyzed at scanned wavelength and the straight line equation was obtained for pH 1.2 and pH 6.8

FTIR Analysis.

Drug-excipient interactions play a vital role with respect to release of drug from the formulation amongst others. In the FTIR studies, Montelukast sodium, combination of Montelukast sodium with excipient, it was observed that all characteristic peaks of Montelukast sodium were present in the combination spectrum, thus indicating compatibility of the drug and excipients. IR spectra are shown in Fig 4-7.

EVALUATION PARAMETERS:

Precompression parameters:

The results obtained in pre-compression studies are summarized in table below.

Postcompression parameters:

The results obtained in pre-compression studies are summarized in table below.

Evaluation of physical parameters of Montelukast sodium core tablets: The physical parameters for all formulations were tabulated in Table 10. All the formulated (F1 to F9) tablets were found within the pharmacopoeia limits. The weights of all the tablets were found to be uniform with low standard deviation values. The measured hardness of core tablets of all the formulations ranged between 3.0±0.1 to 3.1±0.2 kg/cm2 . The % friability was less than 0.7% in all the formulations. The measured thickness of core tablets of each formulation ranged between 2.2±0.05 mm to 2.4±0.02 mm. The disintegration time for coarse tablets laid between 9 seconds to 41 seconds. The wetting time for core tablets ranged from 7 seconds to 21 seconds. The percentage of drug content was found between 94% to 98.6%.

In vitro dissolution studies of core Montelukast sodium tablets:

In vitro drug release of Montelukast sodium from core tablets was determined using USP dissolution testing apparatus II (Paddle type). The dissolution test was performed using 900 ml HCl buffer (pH 1.2) which was replaced with phosphate buffer (pH 6.8) after two hours. Temperature was maintained at 37± 0.50 ºC. The speed of rotation of paddle was set at 50 rpm. At a predetermined time interval of 4 minutes, 5 ml samples were withdrawn, filtered through Whatman filter paper. Absorbance of solution was checked by UV spectrophotometer and drug release was determined from standard curve. The F₆ & F₉ optimized formulation was found to give maximum cumulative drug release of 97.9% in 16 minutes and 98.3% in 12 minutes respectively. The drug release profiles from various formulations are shown in Figure 7-9.

Optimized formulation:

From all the prepared formulations, the best formulation (F6 & F9) was selected based on postcompression parameters and coated with Eudragit S100 and ethyl cellulose.

5.4. EVALUATION PARAMETERS OF COATED TABLETS

In vitro dissolution studies of coated tablet.

The in vitro dissolution studies was performed for the coated tablet for all formulations using a tablet dissolution test apparatus with paddle type at 50 rpm having 2 different buffers of 900 ml i.e pH 1.2 and pH 6.8 buffer as dissolution medium. The pH 1.2 was kept for 2 h as the dissolution medium and then the dissolution medium was changed with the pH 6.8. The samples were withdrawn and were analyzed in the UV spectrophotometer. The results were recorded and the % cumulative drug release was calculated. The results of the dissolution studies showed F₆ and F₉ optimized core tablets as depicted in the table 7. The in vitro dissolution studies showed lag time of 3 h in coated tablet having 24% coat and the coated tablet with 14% coating showed lag time of 2 h. The system released the drug rapidly after a certain lag time due to the rupture of the Eudragit S100 and ethyl cellulose film as shown in Table 9. Absorbance of solution was checked by UV spectrophotometer and drug release was determined from standard curve. The optimized formulation C₂ and C₈ were found to give maximum cumulative drug release of 96.9% and 97.8% in 6 h respectively. The drug release profiles from various formulations are shown in figure 10. Eudragit S100 was selected as coating material because of its pH sensitive nature and its eroding behavior and was applied by dip coating method. The Ethyl cellulose coating formed a film, which could rupture easily upon exposure to the dissolution media of alkaline pH i.e. in body the tablet would release in intestinal pH. The maximum drug release was found optimum when the release was till 6 h i.e if the tablet is taken at 10 pm then it would release till 4 am, which lies between the asthma attack time i.e. within 2 am - 4 am.

Stability studies: The stability study was done by keeping in accelerated temperature. The C2 & C8 formulations were kept for accelerated stability studies under the condition of 40 ºC /75% RH for 30 days. The results are depicted in Table 10 and 11. The stability studies of C2 & C8 showed no significant changes in appearance, drug content and cumulative % drug release was found to be 96.6% & 97.5% respectively after 30 days.

CONCLUSION

In the present study, pulsatile drug delivery system of Montelukast sodium for treatment of nocturnal asthma was formulated. Each tablet contained 10mg of the drug. The study includes preformulation of the drug and excipients, formulation, evaluation and stability studies of the tablets. The pulsatile tablets were prepared in two steps. The first step included preparation of core tablet, which consisted of drug along with different concentration of superdisintegrants, microcrystalline cellulose, lactose and magnesium stearate. The second step was preparation of coated tablet, here the optimized core tablets were selected and subjected for dip coating with different concentration of ethyl cellulose and Eudragit S100. The effect of coating levels of Eudragit S100 and ethyl cellulose was investigated. The coated tablets were evaluated for weight variation, hardness, friability, drug content, disintegration studies and dissolution studies. The optimized formulation C2 and C8 showed drug release of 96.9% and 98.4% drug at 6 h. Then the selected optimized formulations were subjected for stability studies. This coating composition 24% of Eudragit S100 and ethyl cellulose helped achieve a definite nonrelease lag phase. The coated drug delivery system prevented drug release in stomach and released drug rapidly after predetermined lag time in the intestinal tract when pH was above 6. The intention was to administer the formulation at around 10.00 pm so that after a specified lag time the drug is rapidly available in the early morning hours to treat nocturnal asthma. It can be concluded that C2 with 24% of Eudragit S100 coating and C8 with 24% of Ethyl cellulose coating were found to be optimized pulsatile tablets.