Sustained release solid dispersion of Metoclopramide HCL: formulation, evaluation and pharmacokinetic studies

Article history: Received on: 08/10/2014 Revised on: 21/10/2014 Accepted on: 08/12/2014 Available online: 28/03/2015 In recent years oral controlled delivery systems have gained increased importance and interest since it is necessary to improve the systemic absorption of the drugs and patient compliance. In addition, controlled delivery systems maintain uniform drug levels, reduce dose and hence dose related side effect, and increase the safety margin. The objective of present work was prepared sustained release solid dispersion of Metoclopramide HCl by solvent evaporation method. Several polymers like combination of Eudragit RSPO Eudragit RLPO and Guargum-Egg albumin as synthetic and natural polymers respectively were used. Several parameters like Solubility, Partition coefficient, Drug content, Percent drug release, Bulk density, Tapped density and Carr’s index were evaluated and all parameters were found to be in acceptable range. The results of XRD and SEM analysis were showed that the drug was converted into a solid dispersion. The In vivo studies were performed on Albino Wistar rats and various pharmacokinetics parameters were determined. The whole study was showed that the solid dispersion of Metoclopramide HCl sustained the release rate of drug for a prolong period of time at least 12 hrs and shows to increase the bioavailability and simultaneously decrease the dosing interval as well as dosing amount. The formulation minimizes the blood level oscillations, dose related adverse effects and cost and ultimately improve the patient compliance and drug efficiency.


INTRODUCTION
In recent years oral controlled delivery systems have gained increased importance and interest since it is necessary to improve the systemic absorption of the drugs and patient compliance. In addition, controlled delivery systems maintain uniform drug levels, reduce dose, side effects, and increase the safety margin. Sustained release solid dispersion formulations are the most fashionable and straightforward to formulate on a commercial scale. A wide variety of polymer matrix systems have been used in oral controlled drug delivery to obtain a desirable drug release profile, Cost effectiveness, and broad regulatory acceptance (Patel et al., 2012).Sustained release drug delivery are designed to achieve a prolonged therapeutic effect by continuously releasing medication over an extended period of time after administration of single dose of drug (Dusane et al., 2011). The USP and FDA, identify specific dissolution requirements for extended release dosage forms which involve . * Corresponding Author Email: nehasl1990@gmail.com sampling three times, expressed as fractions of the normal dosing interval (D). Releasing of 20-50% of the drug after 0.25 D assures that there is no dose dumping from the dosage form. The intermediate specification assures that drug release (45-75%) over the 0.25-0.5 D period occurs neither too slowly nor too rapidly, while the purpose of the last specification is to assure complete dissolution of the drug. From a practical stand point, sampling through 8 h for a twice daily product and through 12 h for a once daily product may be adequate, provided that not less than 75-80% of drug has been released ( Welling et al., 1988). The selection of is Metoclopramide hydrochloride is used an effective and popular drug for many type of vomiting induced by drug, disease associated(migration), radiation sickness but it less effective in motion sickness. Metoclopramide is used in long term therapy for vomiting induced by highly emetic anticancer drugs (cisplatin, etc). Metoclopramide hydrochloride inhibits gastric smooth muscle relaxation produced by dopamine, therefore increasing cholinergic response of the gastrointestinal smooth muscle. The central antidopaminergic (D2) action of Metaclopramide on CTZ is responsible for its antiemetic property.
It accelerates intestinal transit and gastric emptying by preventing relaxation of gastric body and increasing the phasic activity of antrum. Metoclopramide also decreases reflux into the esophagus by increasing the resting pressure of the lower esophageal sphincter and improves acid clearance from the esophagus by increasing amplitude of esophageal peristaltic contractions. Studies have also shown that high doses of Metoclopramide can antagonize 5-hydroxytryptamine (5-HT) receptors in the peripheral nervous system in animals. Guar gum is a nonionic naturally occurring, hydrophilic polysaccharide obtained from the seeds of Cyamopsis tetragonolobus. It is used in solid dosage forms (binder and disintegrant), possess release retarding property and susceptibility to microbial degradation. It swells in cold water and forms viscous colloidal dispersions or sols. It is this gelling property that retards release of the drug from the dosage form. It was observed that guar gum alone acts as the release retarding polymer which follows a first-order release kinetic ( Anupama et al., 2011).
The increased concentration of guar gum decreases the drug release (Deshmukh et al., 2009). Albumin have been extensively investigated in controlled release polymer as vehicles for the delivery of therapeutic agents to local sites. The exploitable features of Albumin include its reported biodegradation into natural products, its lack of toxicity and its nonantigenicity (Aydan et al., 2012).
Egg Albumin was selected as hydrophilic carriers for this study because of significant differences in their conformation and stability. Several studies on the conformational changes in ovalbumin induced by certain denaturing agents and by chemical modifications of certain amino acid have been reported ( Ifat et al., 2000). In the field of modified drug delivery, interesting potentialities are offered by acrylic polymers, such as Eudragit Retard, extensively used for film coating of solid dosage forms, as well as in the preparation of inert matrices or micromatrices for controlling the drug delivery via oral or other routes. Eudragit RS (RS) and RL(RL) are copolymers of poly(ethyl-acrylate-co methyl-methacrylate-co-trimethylamino-ethyl-methacrylate chloride) [poly(EAMMA-TAMCl)]. The introduction of the hydrophilic ammonium groups (TAMCl) is aimed at modifying the permeability of the acrylic polymer. The main difference in RS and RL consists in the amount of ammonium groups: their composition is in fact EA:MMA:TAMCl=1:2:0.2 (RL) and 1:2:0.1 (RS). These polymers are insoluble in aqueous media, but are able to swell and become permeable to solutes, thanks to the presence of the ionized TAMCl groups, but in a pH-independent manner (Eudragit Technical Sheets, Rohm, Germany) ( Rosario et al., 2004).

MATERIAL AND METHOD
The Metoclopramide HCL was obtained as gift sample from Vaikunth Chemical Pvt Ltd, Gujrat (India). The synthetic polymers Eudragit RSPO and Eudragit RLPO were obtained as a gift sample from Evonic Pvt Ltd, Mumbai (India). The Natural polymers Guargum and Egg albumin was procured from Central Drug House Pvt Ltd, N. Delhi (India). The Potassium dihydrogen phosphate, Hydrocloric acid and di sodium hydrogen phosphate were procured from Central Drug House Pvt Ltd, N. Delhi (India). All chemical and solvent were used of analytical grade.

Formulation Design
The miscellaneous factorial design with independent 2 factors and 3 levels (design expert -8 software, Statease, U.S. A) was apply to design and optimized the delivery system. Total 13 runs with formulation code B1-B13 were obtained. There was two independent factor (Polymer 1and 2) and two dependent factor (% cumulative drug release and drug content uniformity).

Methods
Specific quantity of Metoclopramide HCl, Guargum, Egg albumin, Eudragit RSPO, and Eudragit RLPO were weighed. The mixture of Drug and Albumin, Guargum in different ratio were weighed and was mixed with distilled water use as a solvent. As the same way the mixture of drug, Eudragit RSPO and Eudragit RLPO were mixed with absolute alcohol with continuous stirring to achieve homogeneous mixture in magnetic stirrer at 40 0 C. The solvent was evaporated at 20-40 0 C. After some time the solid residue was remained which was collected and sieved by 80# mesh and was stored in desiccators.

Dose determination
The conventional dose of Metoclopramide HCl is 10mg-15mg four times a day but the dose is reduced to 27mg for formulating sustained release solid dispersion (Hemalatha et al., 2011;Kannan et al., 2010;Sandip et al., 2011). D t = D i (1+0.693*t m /t 1/2 ) Where, D t = total dose; D i = initial dose; t= time to which the drug is sustained; t 1/2 = half life of the drug. D t = 10(1+0.693×12/5); D t = 27mg. After the calculation the 27 mg Metoclopramide is equivalent to 30mg Metoclopramide HCL twice a daily filled in capsule.

Angle of Repose
Angle of repose was determined using funnel method. The blend was poured through funnel that can be raised vertically until a maximum cone height (h) was obtained. Radius of the heap (r) was measured and angle of repose was calculated using the formula (Viral et al., 2011). θ = tan -1 h/r Where, θ is the angle of repose, h is height of pile; r is radius of the base of pile.

Bulk Density
Apparent bulk density (ρb) was determined by pouring the blend into a graduated cylinder. The bulk volume (Vb) and weight of powder (M) was determined. The bulk density was calculated using the formula (Viral et al., 2011).

Tapped Density
The measuring cylinder containing known mass of blend was tapped for a fixed time. The minimum volume (Vt ) occupied in the cylinder and weight (M) of the blend was measured. The tapped density (ρt) was calculated using the following formula (Viral et al., 2011).

Carr's Compressibility Index (I)
The simplest way of measurement of free flow of powder is compressibility, an indication of the ease with which a material can be induced to flow is given by compressibility. The compressibility index of the granules was determined by Carr's compressibility index which is calculated by using the following formula (Viral et al., 2011).

Determination of percent yield
The percent yield of Metoclopramide HCl solid dispersions can be determined by using the following expression (Tyagi et al., 2012). Percent yield = (weight of prepared solid dispersion / weight of drug + carriers) x 100

Drug Content
To determine the actual amount of drug present in each milligram of the formulation. Formulation containing 100 mg drug was taken in 100ml volumetric flask, dissolved in pH 6.8 phosphate buffer and volume was made up to mark with pH 6.8 phosphate buffer then sonicated for 15min. after sonication the solution was filtered. The 1ml sample was pipetted out from the sonicated solution into 10ml volumetric flask then volume was made up the 10 ml with 6.8 phosphate buffer. Absorbance was taken at 272 nm by UV spectrophotometer (Shimadzu 1800, Japan).

In vitro dissolution study
The study was performed by using USP dissolution apparatus I (basket type) at 37 0 C & 100 rpm in 500ml 1.2HCL buffer solution for 2 hour. Then in resting time (10 hrs) the test was performed in 400ml 6.8 phosphate buffer to make up the volume 900ml. The 10ml sample was withdrawn in 30, 60, 90, 120, 150….720min at different interval and filtered. The absorbance of the solution was measured at 272 nm. The concentration of metoclopramide HCl was calculated using slope of calibration curve and cumulative percentage release was calculated.

Infrared spectral analysis
Infrared (IR) spectra of solid dispersion prepared by natural polymers(Guargum +Egg albumin) and synthetic polymers (EudragitRSPO+EudragitRLPO) were obtained by using KBr disc method (1800, Shimadzu Asia Pacific Pvt. Ltd, Singapore) in the range of 4000 to 350cm -1 .

X-Ray diffraction analysis
The X-ray powder diffractograms of the API, solid dispersion, physical mixture of drug and polymers were recorded using glancing angle X-ray diffraction (GAXRD, Cu Kα radiation of wavelength 1.54 Å, Phillips X'pert PROPW 3040, Indian Institute of Technology,Delhi) at a speed of 4 0 / min from 10-60 range (2θ) at sample interval 0.02 0 under the voltage and current of 40 Kv and 30 Kv respectively .

Scanning electron microscopy analysis
The sample was mounted in circular metallic sample holder available with SEMCF be arranged in a circular pattern as displayed in the SEMCF keeping under the vacuum and the sample was coated with gold partical by using BIO-RAD POLARAN sputter coater. The sample was placed in a evacuated chamber and scanned in a controlled pattern by electron beam (ZEISS EVO Series Scanning Electron Microscope EVO 50,IIT Delhi). Interaction of the electon beam with specimen produced a verity of physical phenomenon that detected are used to form images and provided the information about specimen.

In Vivo study
In vivo studies were conducting on albino wistar rats. The approval for studies was given by the animal ethical committee, ITS Paramedical (Pharmacy College), Muradnagar, Ghazaibad, UP, India. Wistar Rats were divided into three groups. The animal was fasted overnight. Drug (formulation equivalent to dose/body weight) was administered orally to each group as a single dose (4mg/kg of Metoclopramide HCL) through oral gauge. Blood sample were withdrawn at predetermined time interval from the orbital plexus of rat and collected in the EDTA coated vacuette tube and then centrifuged at 3000 rpm for 10 min to separate the plasma. Separated plasma was mixed with 4ml of diethyl ether / Acetonitrile to 1 ml plasma sample and mixed .The mixture was again centrifuged for 10 min at 3000 rpm. After centrifugation the upper organic layer is separated and the solvent is evaporated in a oven to dryness. The residue was added in 400µl of mobile phase and evaluated by HPLC (PU-2080Plus Jasco, Japan) (Menaka et al., 2013;Rashmika et al.,2013;Sushilkumar et al., 2011;Zheng et al., 2014).

HPLC analysis
The standard curve between area% v s concentration(ng/ml)of metoclopramide HCL was constructed by using KH 2 PO 4 (0.05M,Ph 4.6) and acetonitrile in ratio of 60:40v/v as mobile phase. The flow rate and duration of run were 1ml/min 10 min respectively. Various pharmacokinetics parameters like AUC, T max C max. etc were determined for both formulation and API and compared.

Compatibility study
The IR spectra of pure drug and physical mixture of drug + polymers (Metoclopramide HCL + Guargum+ Egg albumin and Metoclopramide HCL+ Eudragit RSPO+ Eudragit RLPO) was obtained to determined the compatibility of drug and polymer it was found compatible.
Results and inference of Pre Evaluation and evaluation parameters are given in table 2

In vitro drug release
The in vitro drug release profile of various formulations was indicated the sustained action of formulation. The formulation is sustained for 12 hrs than the API of drug and physical mixture of drug and polymers. The cumulative drug release of pure drug in 60 min was found to be 98% in pH1.2 HCL buffer and 99% in pH 6.8 phosphate buffer.
The cumulative drug release of physical mixture of Drug + Eudragit RSPO+Eudragit RLPO and Drug + Guargum+Albumin in 60 min was found to be 92% and 95% pH1.2 HCL buffer and 96% and 98% pH 6.8 phosphate buffer respectively. But the drug release was retarded in the formulation of solid dispersion prepared by synthetic polymers B3 ( Eudragit RSPO + Eudragit RLPO) and natural polymers B7 (Guargum + Egg albumin) in 60 min was found to be 25.3% and 23.8% respectively. The Dissolution of optimized formulation (B3 and B7) of solid dispersion was prepared by synthetic polymers (Eudragit RSPO + Eudragit RLPO) and natural polymers (Guargum +Egg albumin) in 12 hrs was found to be 95.7% and 99% respectively(Table 3, 4).
As it is shown in tables 5 and 6 Y1, and Y2, were fitted with a quadratic model and significant lack of fit (P < 0.05). The positive sign of the factors represent a synergistic effect on the response, while a negative sign means an antagonist relationship. Phrases composed of two factors indicate the interaction terms and phrases with second-order factors stand for the nonlinear relationship between the response and the variable.

Effect of Independent Variables on % Cumulative drug release for formulation prepared by polymer (Eudragit RSPO and Eudragit RLPO)
The second-order polynomial equation relating the response of (Y1) % Cumulative drug release is given below: Y 1 =+94.08-6.32A-4.98B-5.00AB-1.14A 2 -1.74B 2 The equation in terms of coded factors can be used to make predictions about the response for given levels of each factor. The coded equation is useful for identifying the relative impact of the factors by comparing the factor coefficients. The Model F-value of 137.76 implies the model is significant (p = <0.0001). "Lack of Fit F-value" of 4.55 implies the Lack of Fit is not significant (P= 0.0886). The ANOVA test indicates that A, B, AB & B 2 are significant model terms. Negative coefficients of A, B, AB, A 2 & B 2 indicate the antagonistic effect on %cumulative drug release( Table  5). The "Pred R Squared" of 0.9309 is in reasonable agreement with the "Adj R-Squared" of 0.9828, indicating the adequacy of the model to predict the response of %cumulative drug release. The 'Adeq Precision' of 41.778 indicated an adequate signal. Therefore, this model is used to navigate the design space( Table  6). As the concentration of polymers was increased the total %cumulative drug release of the sustained release solid dispersion gets decreased. In the case of Eudragit RSPO and Eudragit RLPO as its concentration was increased it leads to decreased in % cumulative drug release. Therefore, it was suggested to keep its concentration on the upper side to release sustained effect (Fig. 3a)

Effect of independent variables on Drug content uniformity for formulation prepared by polymer (Eudragit RSPO and Eudragit RLPO)
The second-order polynomial equation relating the response of % drug release (Y2) is given below: Y 2 =+83.32+3.39A-0.74B-3.43AB+7.30A 2 +2.10B 2 The Model F-value of 413.87 implies the model is significant (p= < 0.0001). The "Lack of Fit F-value" of 1.01 implies the Lack of Fit is not significant (P=0.4772).The ANOVA test indicate that A, B, AB, A 2 , B 2 are significant model terms. Positive coefficients of A, A 2 & B 2 indicate the synergistic effect on drug content uniformity. Negative coefficients of B, & AB indicate the antagonistic effect on drug content uniformity ( Table  5).
The "Pred R-Squared" of 0.9828 is in reasonable agreement with the "Adj R-Squared" of 0.9942. indicating the adequacy of the model to predict the response of drug content uniformity. The 'Adeq Precision' 61.277 of indicated an adequate signal. Therefore, this model is used to navigate the design space ( Table 6).
As it is shown in tables 7and 8, Y1, and Y2, were fitted with a quadratic model and insignificant lack of fit (P > 0.05). The positive sign of the factors represent a synergistic effect on the response, while a negative sign means an antagonist relationship. Phrases composed of two factors indicate the interaction terms and phrases with second-order factors stand for the nonlinear relationship between the response and the variable.

Effect of Independent Variables on % Cumulative drug release for formulation prepared by natural polymers (Guargum + Egg albumin)
The second-order polynomial equation relating the response of (Y1) % Cumulative drug release is given below: Y 1 =+95.17-6.48A-2.05B-2.12AB-5.09A 2 +2.11B 2 The equation in terms of coded factors can be used to make predictions about the response for given levels of each factor. The coded equation is useful for identifying the relative impact of the factors by comparing the factor coefficients.
The Model F-value of 66.21 implies the model is significant (p= < 0.0001). "Lack of Fit F-value" of 6.58 implies the Lack of Fit is not significant (P= 0.0501). The ANOVA test indicates that A, B, AB,A 2 ,B 2 are significant model terms. Positive coefficients of B 2 in equation (1) indicate the synergistic effect on % cumulative drug release while negative coefficients of A, B, AB & A 2 indicate the antagonistic effect on %cumulative drug release (Table. 7).
The "Pred R Squared" of 0.8398 is in reasonable agreement with the "Adj R-Squared" of 0.9645, indicating the adequacy of the model to predict the response of %cumulative drug release. The 'Adeq Precision' of 24.879 indicated an adequate signal. Therefore, this model is used to navigate the design space (Table. 8). As the concentration of polymers was increased the total %cumulative drug release of the sustained release solid dispersion gets decreased. In the case of Guargum and Albumin as its concentration was increased it leads to decreased in %cumulative drug release. Therefore, it was suggested to keep its concentration on the upper side to release sustained effect (Fig 4.a).

Effect of independent variables on Drug content uniformity for formulation prepared by natural polymers (Guargum + Egg albumin)
The second-order polynomial equation relating the response of % drug release (Y2) is given below: Y 2 =+92.76-3.18A-2.09B-3.82AB-2.45A 2 -0.75B 2 The Model F-value of 40.29 implies the model is significant (p= < 0.0001). The "Lack of Fit F-value" of 3.94 implies the Lack of Fit is not significant (P=0.1092). The ANOVA test indicates that A, B, AB & A 2 are significant model terms. Negative coefficients of A, B, A 2 , B 2 & AB indicate the antagonistic effect on drug content uniformity( Table  7).
The "Pred R Squared" of 0.7732 is in reasonable agreement with the "Adj R-Squared"0.9424, indicating the adequacy signal of the model to predict the response of drug content uniformity. The 'Adeq Precision' 22.372 of indicated an adequate signal. Therefore, this model is used to navigate the design space (Table 8).

Infrared spectral analysis
IR spectroscopy was performed on pure drug Metoclopramide HCL and its solid dispersion. Pure MCP spectra showed sharp characteristic peaks at 2977.55(C-H stretching in CH 3 group), 3216.68(N-H stretching in NH2 group), 1731.76(C=Ostretching in C=O group), 624.8(C-Cl alkyl halides group) and1508.06(C-C stretching in aromatic ring) cm -1 . All the above characteristic peaks appear in the spectra of Metoclopramide HCl solid dispersion prepared by natural polymer Guargum+Eggalbumin and synthetic polymers (Eudragit RSPO+ Eudragit RLPO) at same wave number indicating no modification or interaction between the drug and polymers (Fig 5).

X ray diffraction analysis
The retardation of peaks height or no peak observation in XRD of optimized formulation prepared by synthetic polymers B3 (Eudragit RSPO-Eudragit RLPO) natural polymers B7 (Guargum-Albumin) was found that the crystalline pure drug was completely changed into amorphous solid dispersion (Fig 6).

Scanning electron microscopy analysis
The SEM analysis was also used to determine the surface structure of solid dispersion. The structure of optimized formulation prepared by synthetic polymers B3 (Eudragit RSPO-Eudragit RLPO) natural polymers B7 (Guargum-Albumin) was found to be amotphous after comparison with drug structure (Fig 7).

In vivo study
The pharmacokinetic graph between between concentration (µg/ml)v s time(hrs) was shown that increased sustained effect of Formulation prepared by synthetic polymers B3 (Eudragit RSPO+ Eudragit RLPO) and optimized formulation prepared by natural polymers B7 (Guargum+ Egg albumin) over the effect of pure drug over the effect of pure drug (Fig 8). The in vivo study of solid dispersion of Metoclopramide HCl was done for determination of pharmacokinetic parameters of solid dispersion of Metoclopramide HCl and was compared with pharmacokinetic parameter of pure drug Metoclopramide HCl (Table 10).   (a) (b) Fig. 4: 3-D surface response plots showing relative effects of Guargum and Egg albumin on (a) percent Cumulative drug release (b) drug content uniformity for formulation B1-B13 prepared by Guargum and Egg albumin.

CONCLUSION
In this study, the statistical analysis of cumulative drug release and drug content uniformity shows that the solid dispersion of Metoclopramide HCl sustained the release rate of drug for a prolong period of time 12 hrs and shows shows to increase the bioavailability and simultaneously decrease the dosing interval as well as dosing amount. The formulation minimizes the blood level oscillations, dose related adverse effects and cost and ultimately improve the patient compliance and drug efficiency.The in vivo study show that the the half life of soild dispersion was increased than the API of metoclopramide HCl.As well as the study show that both formulation prepared by separately synthetic and natural polymers are produced sustained release drug profile but formulation prepared by eudragit RSPO and eudragit RLPO is more sustained than formulation prepared by Guargum and Egg Albumin.