Factorial Design Based Optimisation of Metoclopramide Hydrochloride Fast Dissolving Tablets

Introduction

Metoclopramide hydrochloride [4-amino-5-chloro-N-(2-diethyl amino ethyl-2-methoxybenzamide) hydrochloride monohydrate] is a dopamine receptor antagonist. Metoclopramide hydrochlorideacts as antiemetic and gastroprokinetic agent, commonly used to treat nausea and vomiting.¹ It increases gastric peristalsis while relaxing first part of duodenum- speeds gastric emptying. ² Generally emesis is preceded with nausea and in such a condition, it becomes difficult to administer drug with glass of water; As Metoclopramide is intensely bitter, it cannot be incorporated directly into mouth dissolving tablets.³ Hence taste masking becomes essential for bitter drugs to improve the patient compliance particularly in the pediatric and geriatric population and there by contribute for commercial success of the product. Different methods are available to mask undesirable taste of  the drugs, like adding sugars, flavours, sweeteners, coating drug, solid dispersion etc.⁴ Taste masking techniques such as physical barrier coatings, chemical modification and sensory masking have been developed. Among chemical modification, the inclusion complexation of drugs with cyclodextrins can provide the effective bitter taste masking effects without complicated formulation and delayed dissolution of drugs.⁵ Kneading method is the frequently used simple method to prepare the inclusion complexes such as cyclodextrins and it presents very low cost of production.⁶ There has been an increased demand for a lot of patient-convenient and compliant dosage forms in the market for the past few decades, because demand for developing new technologies has been increasing day by day.⁷ Fast dissolving tabletsor orally disintegrating tablets; (ODT) has emerged as suitable alternative to other oral dosage forms. These are unconventional types of tablets that disintegrate/dissolve/ dissipate in the saliva within few seconds.⁸ FDT’s may contain sweeteners for taste masking. United States Food and Drug Administration (USFDA) outlined FDT as “A solid dose type containing a medicative substance or active ingredient that disintegrate quickly sometimes within a few seconds once placed above the tongue”.⁹ Earlier, any new pharmaceutical formulation was designed by investigating the impact of formulation and process factors on dosage form characteristics, changing one single or more factor at one time, while keeping others constant, this technique was also called as adjusting one variable at one time or one factor at one time. By this technique, problem may be solved but it does not guarantee the true optimum concentration or process and the product obtained may be suboptimal. ¹⁰ So, in order to overcome these errors a novel approach was followed, which is optimization technique, that involves systematic Experimental design.¹¹ Factorial experiments such as two-level factors are commonlyused as they are easy to design, practical to run, precise to analyze, and filledwith information. Full factorial design comprises of all possible compositions of a list of factors and is the reliable full proof design approach.¹² Hence the present research is an effort to develop FDT of taste masked Metoclopramide hydrochloride by 2³ factorial design method.

Materials and Methods

Metoclopramide hydrochloride was gifted from Caplinpoint Laboratories Ltd. Puducherry.β Cyclodextrin was obtained from Ajanta Pharmaceuticals, Mumbai. Crospovidone,Sodium starch glycolate andCroscaramellose sodium were received from Helios Pharmaceuticals, Gujarat. Potassium dihydrogen orthophosphate and Micro crystalline cellulose were purchased from S.D Fine Chemicals Pvt Ltd, Mumbai. All other chemicals used were of analytical grade.

Taste masking of Metoclopramide hydrochloride by Complexation with β Cyclodextrin: 

Complexation of Metoclopramide hydrochloride was done by kneading method using drug and β Cyclodextrin in different ratios of 1:1, 1:2, 1:3, 1:4, 1:5 and 1:6, respectively. Drug and β Cyclodextrin were kneaded for specific time. The kneaded mixture was dried upby drying at room temperature. The resultant mass was passed through sieve no.16 and stored in a desiccator.¹³ The composition of taste masked Metoclopramide hydrochloride β Cyclodextrincomplexes is given in Table 1.

*DC1- drug β Cyclodextrin complex

Characterisation of Taste masked Complexes: Drug content

Drug complex (70 mg) containing 10 mg of Metoclopramide hydrochloride was accurately weighed and transferred into 100 ml volumetric flask. Phosphate buffer of pH 6.8 was added to dissolve the drug complex and the resulting solution was passed through Whatman filter paper no.41. The collected filtrate was suitably diluted with buffer and observed under uv-spectro photometer at 272 nm againist blank to know the drug content.¹⁴

In vivo Taste Evaluation

In vivo taste evaluation study was initiated after obtaining the Institutional Research Ethical Clearance approved by Institutional Research Ethical Committee of Navodaya Medical College, Raichur. Informed consent from the subjects was taken before including them in the study.

The drug complex was tested for taste by six healthy adult volunteers. Complexation of Metoclopramide hydrochloride prepared by using β Cyclodextrin in different ratios were tested for taste masking.

The volunteers rinsed their mouth cavities sufficiently pre and postto tasting the complex with distilled water. The prepared complexes were kept in the volunteer’s mouth over 30 sec and then spit out. Mouth was thoroughly rinsed before the next test. The taste score was fixed to the extent of 0-4 depending on the degree of taste masking (0-Pleasant, 1-Tasteless, 2-Slightly bitter, 3-Moderately bitter, 4- Extremely bitter.) The best taste masked complex was selected as optimized on the basis of scores. Pure drug Metoclopramide hydrochloride was taken as control.^{15, 16}

Fourier Transform Infrared Spectroscopy (FTIR) analysis

The Pure drug, Optimized taste masked complex DC6 were tested for FTIR analysis to check the compatibility/interaction between the drug and carrier. The samples were prepared on KBr-press (Agilent Technologies Hyderabad, INDIA). The specimens were scanned between 4000-600 cm^-1 and spectra were interpreted for any drug carrier interactions.

2³ factorial design to develop Metoclopramide hydrochloride FDTs:

Factorial design was used in this experiment to know the effects of different conditions or factors on experimental results. 2³randomized full factorial design was developed by using concentration of superdisintegrantsas factors or independent variables i.e., Sodium starch glycolate(X1-SSG), croscarmellose sodium (X2-CCS) and crospovidone(X3-CP) and time ofdisintegration (Y1),percentage drug release (Y2) as dependent variables. For each of these factors, 2-levels were used (Table 2). 2³ factorial studies were designed to determine the interaction of three independent variables at two levels (low and high level concentration). Eight formulations employing selected combinations of the three Factors as per 23 Factorial designs were formulated (Table3). The optimised formula F9 was developed after interpreting the eight formulations.

Preparation of Taste Masked Metoclopramide hydrochloride FDT’s:

Drug complex about 70 mg (equivalent to10 mg of pure drug) was taken in a plastic containerand mixed with diluents, super disintegrants and sweeting agents which were previously passed through sieve no.40. Magnesium stearate and aerosol were passed through sieve no.80, and incorporatedin to the container to get homogenous mixture.The powder blend was then compressed by a 10-station rotary compression machine using 4 mm flat punches to give FDT’s.¹⁷ The formulae of FDT’s (F1-F8) arepresented in the Table 4. 

*70 mg of Metoclopramide hydrochloride DC contains 10 mg of pure Metoclopramide hydrochloride drug

Evaluation of Taste Masked Metoclopramide Hydrochloride FDT’s:

Thickness and Diameter

Thickness and Diameter of prepared tablets (10 nos) were tested using Vernier callipers.

Hardness

The hardness of tablets (5 nos) was tested by Monsanto hardness tester in terms of kg/cm².

Friability

The test was carried out to assess the influence of friction and shocks on tablet strength, which may often cause tablet to chip, cap or break. Roche friabilator was employed to test the friability of prepared fast dissolving tablets. 10 preweighedtablets were placed in the friabilator and it was run for 100 revolutions. The tablets were reweighed after de-dusting.

Friability (F) was measured byapplying the formula:

%F = (Wo- W/ Wo) × 100---------- (1)

where, Wo and W are the weight of the tablets before after the test respectively. The test was done in triplicate. Tablets that lost less than 1% weight were acceptable as per specifications.

Weight Variation

The prepared tablets were taken (20 nos) and their individual and average weights were noted on a weighing machine (Shimadzu digital balance). To know the weight variation, percent deviation was computed using the formula:¹⁸

% Deviation= (Individual weight-Average weight) / Average weight X 100 --------- (2)

The permissible limits ofpercent deviation for weight variation should be within 7.5%.

Drug Content

Weighed tablets (5nos) were powdered using a glass mortar and pestle. Tablet powder corresponding to 10 mg of drug was transferred to 50 ml volumetric flask containing phosphate buffer of pH 6.8 and the drug was dissolved by shaking. The solution was then filtered using Whatman filter paper no.41. The filtrate was taken and after suitable dilution with buffer was subjected to UV-spectrophotometer (UV-1700 Shimadzu Corporation, Japan) to obtain drug content.

Wetting time

In a small Petri dish (internal diameter = 6.5 cm) containing 5 ml of distilled water, a section of tissue paper folded twice was placed. On the tissue paper, at the centre of petri dish, a tablet was placed, and the complete wetting time of the tablet was measured.  

Water Absorption Ratio

In a small Petri dish (internal diameter = 6.5 cm) containing 5 ml of distilled water,asection of tissue paper folded twice was placed. On the tissue paper, a tablet whose weight noted was placed. The tablet was allowed to wet and then was weighed again. The water absorption ratio (R) was determined according to the following equation:

R = Wa– Wb / Wa X 100 --------- (3)

where, W_b is the tablet weight prior to test and W_a is the tablet weight post water absorption. 

Disintegration test

Six tablets along with disc were introduced in each tube of basket of disintegration test apparatus (Lab care instruments). The basket was positioned into a beaker containing 900 ml of distilled water and operated at 37±0.5^o C. The time of disintegration of tablet was recorded.^{19, 20} 

In vitro drug release study

In vitro dissolution study was performed in a 8 station USP (Type-II) dissolution apparatus (Electro Lab, TDT-O8L, Mumbai). 900 ml of phosphate buffer pH 6.8 was used as medium. The medium was stirred at 50 rpm with paddle and temperature was maintained at 37 ± 0.5^o C. Every 2 min, 5 ml of aliquot was collected and instantly replaced by same volume of fresh medium. The aliquots after suitable dilution were assessed by UV spectrophotometer at 272 nm for amount of drug released.

Analysis of Data

The data obtained from disintegration time and dissolution rate study wasanalysed as per ANOVA. It was used to figure out the significance of individual and combined effects of the three factors on the dependent variables. Further to envision the influence of independent factors X1X2X3 on dependent variables Y1-disintegration time and dissolution rate Y2, Contour plots and three-dimensional (3D) plots were developed based on the polynomial model.

Results and Discussion

The aim of this research was to reduce the bitter taste of Metoclopramide hydrochloride by inclusion complexation technique and use of flavouring agent. The complex so formed was used in formulating FDT of drug using different super disintegrants adopting 2³ factorial design method. The drug complex was prepared by kneading method; in which drug and β Cyclodextrin were mixed in different ratios of 1:1, 1:2, 1:3,1:4,1:5 and 1:6, respectively.

Characterisation of Taste masked Complexes:

Drug content Drug content of complexes was found to be 6.41 - 13.7 mg/ml, respectively for different complexes.

In vivo Taste Evaluation

The drug β Cyclodextrin complexes prepared in different ratio were given to panel of healthy human volunteers to evaluate the taste by time intensity method (Institutional Research Ethical Clearance was approved by the Institutional Research Ethical Committee of Navodaya Medical College, Raichur). Bitterness was recorded immediately according to the bitterness scale. Depending on intensity of taste values were given from 0 to 4, where 0-Pleasant, 1-Tasteless, 2-Slightly bitter, 3-Moderately bitter, and 4-Extremely bitter. Table 5 indicates the outcome of taste masking evaluation of the Drug-Complexes. The in vivo taste masking evaluation study showed that the total score = 0 for DC6 indicating it had a pleasant taste and its bitterness was successfully masked. Henceforth the complexDC6 was further used to prepare fast dissolving tablet of Metoclopramide hydrochloride.

*DC1- DC6: drug complexes

Fourier Transform Infrared Spectroscopy (FTIR) analysis

The FTIR spectrum of the pure drug Metoclopramide hydrochloride and Optimised Taste masked Drug β Cyclodextrin complex DC6 (Fig. 1 and 2) was observed for presence of any interaction. All peaks corresponding to the functional group and various bonds of pure drug have appeared in their respective positions without much variation in the band positions. Hence it was evident that there was no interaction between drug and carrier βCyclodextrin.

Evaluation of Taste Masked Metoclopramide hydrochloride FDT’s

Physico-chemical evaluation of tablets  

The tablets were tested for various physicochemical properties. The thickness of prepared tablets was between 4.4±0.31 - 4.6±0.20 mm. The diameter of tablets was between 7.0±0.10 - 7.0±0.20 mm and was uniform for all tablets. Hardness of tablets was between 4.7±0.12 -5.0±0.20 kg/cm2 for all the formulations. Friability was found in between 0.07±0.22 - 0.83±0.24%. The value below 1% showed the compactness and strength of tablets. The weight variation of tablets was within the specified limits. The results are presented in Table 6.

Drug content of tablets was between 9.40±0.36 -10.46±0.21 mg which was within the acceptable limits. Dissolution of a tablet is dependent on wetting and disintegration time. Wetting time evaluation may be another confirming test for checking FDTs thus promoting bioavailability. Wetting time is related to inner structure of tablet and hydrophobicity of components.²¹ Wetting time indicates the easiness with which tablet disintegrates in buccal cavity. Wetting time was in the range of 14.00±0.24 to 31.60±0.40 sec for prepared tablets. The tablets disintegrated faster with quick wetting properties at the core of the tablet. Water absorption ratio was between 54.30±1.40 to 75.10±1.10%. Tablets with less wetting time have shown higher water absorption ratio. The results are presented in Table 7.

The most important parameter that is needed to optimize during the development of fast dissolving tablet is disintegration time. Disintegration time is very important for the FDT which is desired to be less than 4 min for orally disintegrating tablet. Disintegration time was in the range of 8.24±0.46 to 90.00±0.70 sec (Table 7). In case of formulation F5, all the three variables are in low concentration (-1) and the disintegration time was 51.00±0.65 sec, and in formulation F8, all three variables at high level (+1) and the disintegration time was 10.82±0.31 sec, indicating disintegration time of tablets is decreased by increasing superdisintegrant concentration. This rapid disintegration assists swallowing and also plays a role in drug absorption in buccal cavity.

In vitro release study

The in vitro dissolution of Metoclopramide hydrochloride FDT’s was studied in pH 6.8 phosphate bufferby paddle method using USP XXIV dissolution test apparatus. The cumulative percentage release for different formulations is given in Fig. 3. FDT’s F8 and F9 showed maximum drug release of 99.06% and 99.26%, over a period of 12 min. In case of formulation F5, all the variables are in low concentration (-1) and the drug release is 96.83%, and in formulation F8, all three variables at high level (+1) and the drug release is 99.06 % pointing out the release of drug is influenced by superdisintegrant concentration. Formulations F1, F2 & F6 have any one of three variables at high level and release of drug was 95.68%, 97.51% and 97.90%, respectively. Formulations F3, F4, & F7 have any two of three variables at high level and the drug release is 98.49%, 97.31 % and 98.52 %.  

Optimization of Taste Masked Metoclopramide hydrochloride FDT’s using 2³ factorial design:

The main goal of optimization techniques is to follow systemic way for the optimum values of variables so that the response is maximized. In the present study, Taste Masked Metoclopramide hydrochloride fast dissolving tablet formulations were optimised using 2³ Factorial design. Different amounts of three superdisintegrants Sodium starch glycolate (SSG), croscarmellose sodium (CCS) and crospovidone (CP) were taken as factors. The disintegration time and dissolution rate were the observed responses. Overview of the experimental trial and observed responses is presented in Table 8. 

Analysis of Data

To investigate the influence of 3 factors,full factorial design was used; polynomial equation was deduced to study the impact of independent variables upon the responses i.e.,disintegration time and % drug release.Inference on results is obtained by regression equations after considering the magnitude of the coefficient and the sign of coefficient indicates the type of response. Positive sign in the polynomial equation infers that the response increases with increase in the value and negative sign shows the decrease in response with increase in the value. The kind of response when two factors were changed simultaneously is given by interaction terms.

Effect of independent factors on disintegration time (Y1)

Y1 = +49.45–6.34 X1 –9.41 X2 - 3.38 X3 –9.88 X1X2 –11.88 X1X3 +11.88 X2X3 +7.78 X12 –9.01 X2² –12.02 X3²------------ (4)

Based on this polynomial equation, it was concluded that factors X1 (SSG), X2 (CCS) & X3 (CP) decrease disintegration time with increase in concentration. Factors X1X2 and X1X3 have a synergistic effect and decrease the disintegration time together which can be observed with a negative sign of the coefficient –9.88 X1X2 and –11.88 X1X3. But it is observed that factors X2X3 increase the disintegration time.

The significant effect was identified by ANOVA, Coefficient of determination R² = 0.9632. The result obtained was significant at that level of probability (p<0.05) since the value of F was larger than critical F-value.As the critical value for F is 4.19 and obtained F value is 26.395 is larger than critical value, it was confirmed that obtained F value is likely to occur by chance with a p<0.05 i.e. indicates significance at that level of probability. A P-value less than 0.05 conclude model terms are significant. Here the model is significant as p-value of model is 0.0340. The Correlation Coefficient R² of 0.9632 indicates desirability near to 1 in design space. The signal to noise ratio is measured by Adeq Precision and a ratio of greater than 4 is desirable. The model ratio of 5.223 indicates an adequate signal. Hence the model can be utilised to navigate the design space. Table 9 displays the results of ANOVA.

Effect of independent factors on dissolution (Y2)

Y2 = 97.14 + 0.631 X1 + 0.055 X2 + 0.245 X3 - 0.550 X1X2 + 0.400 X1X3 + 0.600 X2X3 + 0.265 X₁² - 0.229X₂²+0.513 X₃²--------- (5) 

Based on this polynomial equation,it can be concluded that factors X1, X2 & X3 with positive sign of the coefficient, increases drug release with increase in concentration and factor X1X3, X2X3 have a synergistic effect and enhance drug release, whereas factor X1X2 with a negative sign of the coefficient has antagonistic effect and decreases the drug release.

The significant effect was identified by ANOVA, Coefficient of determination R² = 0.9478. The result obtained was significant at that level of probability (p<0.05) since the value of F was larger than critical F-value. As the critical value for F is 4.19 and obtained F value is 29.966 is larger than critical value, it was confirmed that obtained F value is likely to occur by chance with a p<0.05 i.e. indicates significance at that level of probability. F-value of model is 29.966; this corresponds to P-value of 0.0386. P-values less than 0.0500 conclude model terms are significant. Here the model is significant as P-value of model is 0.0386.

The Correlation Coefficient R² of 0.9478 indicates desirability near to 1 in design space. The signal to noise ratio is measured by Adeq Precision and a ratio of greater than 4 is desirable. The model ratio of 6.012 indicated an adequate signal. Hence the model can be utilized to navigate the design space. Table 10 displays the results of ANOVA for dependent variable i.e., dissolution rate.

To graphically demonstrate the influence of each factor on responses, the contour plots were generated using Design Expert software. The contour plots showing effect of different independent variables on dependent variable i.e., disintegration time (Y1) are presented in Fig. 4-6, and those affecting dissolution rate are given in Fig. 7-9. In case of disintegration time it is noted that increase in X1 (SSG), X2 (CCS) & X3 (CP) decrease the disintegration time. An increase in amount of X1 (SSG), X2 (CCS) & X3 (CP) increases the rate of dissolution.

Response surface (3D) plot is a graphical illustration of the potential relationship between three variables similar to contour plots, 3D surface plot is useful for establishing the response values but in a more precise manner. The response surface graphs illustrating effect of independent variables on disintegration time is shown in Fig. 10-12 and that affecting dissolution rate are given in Fig.13-15.

The required response was predicted by optimization of formula using the contour plots. Optimisation was done to know the exact amount of SSG, CCS and CP required for achieving desired response. Desirability of 1.0 showed that optimal formulation was achieved at 15.6 mg of SSG, 9.80 mg of CCS and 9.40 mg of CP.To confirm this, Taste Masked Metoclopramide hydrochloride FDT (F9) tablets were developed utilising the optimal levels of SSG, CCS and CP and evaluated. To prove the theoretical prediction, disintegration time and in vitro drug release studies were performed on the prepared optimized formulations. The tablets disintegrated in 8.24±0.46 sec and released 99.262% of drug. For each response the relative errors (%) between the predicted and experimental values were calculated and were found within limits. The experimental values were in accordance with the predicted values substantiating the model predictability and validity.

Conclusion

Taste Masked Metoclopramide hydrochloride FDT’s were successfully developed by response surface methodology based on 2³ factorial design. The results suggest that kneading technique can be used to mask bitter taste of drugs. The influence of superdisintegrants X1 (SSG), X2 (CCS) & X3 (CP) amount on the properties of tablet like disintegration time and drug release were analyzed and optimized. The amount of superdisintegrants significantly affected the dependent variables. These developed tablets disintegrated within 5 min, which isadvantageous over the conventional tablets and increase patient acceptance due to taste masking of drug. 

Acknowledgement

Authors are thankful to Dr. R. H. Udupi, Dr.Sunil Kumar B, NET Pharmacy College, Raichur for providing help to carry out this research.

Conflict of Interest

None declared.