Surface Response Methodology for Development and Optimization of Aceclofenac Pulsatile Release Drug Delivery System

Mohd Abdul Hadi¹*, Md Saleem¹, A Srinivasa Rao², Vinay Umesh Rao³

¹Dept of Pharmaceutics, Bhaskar Pharmacy College, Moinabad, R.R District, Hyderabad-500075, India.

²Dept of Pharmacy Practice, Bhaskar Pharmacy College, Moinabad, R.R District, Hyderabad-500075, India.

³Institute of Pharmaceutical Sciences, PJR Enclave, Madhavpuri hills, Chandanagar, Hyderabad.

*Corresponding Author E-mail: hadi.lcp@gmail.com

ABSTRACT:

The current work focuses on the development and optimization of Aceclofenac pulsatile release (PR) drug delivery system using surface response methodology. The drug release was controlled by formulating it into pulsatile release drug delivery system. The formulae was developed using various individual concentrations and grades of polymers for Aceclofenac PR tablets. The compatibility of polymers along with pure drug Aceclofenac was evaluated using FTIR and DSC studies. The tablets were prepared and Pre- and Post-compressional parameters, In-vitro dissolution testing and stability studies were evaluated. The FT-IR and DSC spectras confirms the absence of chemical interaction between drug and polymers. All the Pre-compressional and Post-compressional parameters were found to be in limits. From the dissolution testing of all these formulations, the low and high level of polymer concentrations which were within the range of Target product profile was determined. The design space as defined by the above experiments is within 37.5 to 45 range of the total polymer concentration. The data for stability studies revealed that no considerable differences in drug content and dissolution rates for a period of 6 months as per ICH guidelines. Thus, it was found to be stable. Based on the above results, a design space for both the polymers was successfully developed within which when the mini-tablets are fabricated, the target product profile will always be achieved.

KEYWORDS: Rheumatoid arthritis; Aceclofenac; Pulsatile release drug delivery system; Surface response methodology.

INTRODUCTION:

Rheumatoid arthritis is an autoimmune disease that results in a chronic, systemic inflammatory disorder that may affect many tissues and organs, but principally attacks flexible (synovial) joints. It can be a disabling and painful condition, which can lead to substantial loss of functioning and mobility if not adequately treated [1]. The cardinal signs of rheumatoid arthritis are stiffness, swelling and pain of one or more joints of the body characteristically most severe in the morning [2].

The peak symptoms of rheumatoid arthritis are associated with pain at the time of awakening and these clinical circadian symptoms are supposed to be the outcome of altered functioning of hypothalamic pituitary adrenocortical axis. It has been recommended rheumatoid arthritis can be treated by the concept of Chronopharmacotherapy to ensure that the highest blood levels of drug coincide with the peak pain and stiffness.

A pulsatile drug delivery system that can be administered at night (i.e. before going to bed) but that releases drug in early morning hours would be a promising chronopharmaceutic system [3-5].

Aceclofenac is a non selective COX inhibitor for the treatment of Rheumatoid arthritis. The main drawback of conventional Aceclofenac formulation is that after oral administration the drug is rapidly absorbed, distributed extensively bound to albumin and eliminated with a terminal half-life of 3-4 hrs [6.7].

The design of experiments (DOE) is an efficient procedure for planning experiments so that the data obtained can be analyzed to yield valid and objective conclusions. Whereas, the design space is that established range of process parameters and formulation attributes that have been demonstrated to provide assurance of quality. It forms the linkage between development and manufacturing design. Thus, Response surface methodology requires minimum experimentation and time proving to be more effective and cost-effective than the conventional methods of formulating sustained release dosage forms [8-11]

The current work focuses on the development and optimization of Pulsatile release Aceclofenac mini-tablets using surface response methodology. The developed formulation will improve the bioavailability of Aceclofenac during the time of its greatest need and specifically targets the early morning peak symptoms of Rheumatoid arthritis. The targeted product profile was pre-determined in such a way that it should release maximum concentration of drug in between 6-8 hours of post-dosing.

MATERIALS AND METHODS:

Materials:

Aceclofenac were obtained as a gift sample from IPS Pharma training institute, Hyderabad. Eudragit L100, Eudragit S100 and Microcrystalline cellulose (PH 102) were purchased from Rajesh chemical, Mumbai. Magnesium stearate was purchased from Himedia chem. Lab. Mumbai. Aerozil was purchased from Sisco research laboratories Pvt. Ltd. Mumbai. All other materials used were of analytical grade.

Experimental Methods

Excipients compatibility study:

FT-IR Studies: FT-IR studies were performed and the spectras were recorded in the wavelength region of 4000 to 400 cm^-1. The procedure consisted of dispersing a sample drug, polymers and mixture of drug and polymers in KBr and compressing into discs by applying a compaction pressure 400 psi for 2 min in a KBr press. The pellet was placed in the light path and the respective spectrums were obtained.

Differential Scanning Calorimeter (DSC):

Differential Scanning Calorimeter (DSC) allows the fast Evaluation of possible incompatibilities, because it shows changes in the appearance, Shift of melting endotherms and exotherms, and/or variations in the corresponding enthalpies of reaction. The DSC thermograms of pure drug and its combination with other polymers were recorded. The thermal analysis was performed over a temperature range of 30°C to 350°C.

Formulation Development of Aceclofenac mini-tablets:

Mini-Tablets of Aceclofenac were prepared by direct compression method. All ingredients (Drug Aceclofenac, polymer, MCC PH 102) were passed through a 30 mesh sieve, weighed and blended. The formulations F1-F12 were prepared by varying the individual concentrations (5-60 %) of Eudragit L-100 and Eudragit S-100 polymers. These mixtures after lubricating with Magnesium stearate and Aerosil were compressed to mini-tablets weighing 25 mg using 3 mm circular standard concave punches.

Design of Experiment:

Based on the above results, a 3² full factorial design in a tablet press was developed to study the interdependency of the 2 factors (Eudragit L-100 and Eudragit S-100) on the percentage dissolution of Aceclofenac mini tablets in 0.1N HCl, pH 6.5, 6.8 and 7.2 media.

Table 1: Formulation Design of Critical Process Parameters

Ingredient	Low (%)	Medium (%)	High (%)
X	10	20	30
Y	10	20	30

X=Eudragit L-100 Y=Eudragit S-100

Table 2: 3² Design of Aceclofenac mini-tablet formulations

Experimental runs	X	Y
F13	L	L
F14	L	M
F15	L	H
F16	M	L
F17	M	M
F18	M	H
F19	H	L
F20	H	M
F21	H	H

Evaluation of powder blend characteristics [12]:

Aceclofenac powder blend of different formulas from F1to F24 were evaluated for angle of repose, bulk density, tapped density, Hausner ratio, Carr’s index.

Evaluation of tablet characteristics [12]:

Aceclofenac mini-tablets of different formulas from F1to F24 were evaluated for Weight variation, Tablet hardness. Friability and Uniformity of thickness.

Drug content uniformity [13]:

Thirty two mini-tablets weighted and crushed in a mortar then weighed powder contained equivalent to 100 mg of drug transferred in 100 ml of pH 7.2 phosphate buffer to give a concentration of 100 µg/ml. Take 15 ml of this solution and diluted it up to 100 ml with pH 7.2 phosphate buffer solution to give a concentration of 15 µg/ml. Absorbance measured at 273 nm using UV-Visible spectrophotometer.

In- vitro dissolution studies [13]:

Dissolution studies were carried out in a USPXXIII Electro-lab dissolution apparatus basket type in 900 ml of medium at 37 ⁰C at a rotation speed of 100 rpm. Sixteen mini-tablets equivalent of 100 mg of Aceclofenac after filling in a size ‘0’ hard gelatin capsule were transferred to the dissolution medium. Samples of dissolution medium (5ml) were withdrawn through a filler of 0.5μm at different time intervals, suitably diluted and assayed for Aceclofenac by measuring absorbance at 273nm using UV-Spectrophotometer. The dissolution experiments were conducted in triplicate. For all tests 5ml samples of the test medium were collected at set intervals (2, 3, 4, 5, 5.5, 6, 7, 8, 10, 12 hrs) and were replaced with equal volume of respective dissolution mediums.

For formulation F1-F12, a separate dissolution testing was performed in individual dissolution mediums in pH 1.2 (HCl 0.1N), pH 6.5, 6.8 and 7.2 (phosphate buffer) to determine the concentration range of polymers to be taken in combinations. Then after determination of concentration range, a 3² full factorial design of experiments were used.

Figure 1: FTIR spectra of (a) Pure drug Aceclofenac (b) Eudragit L100 (c) Eudragit S100 d) Physical mixture of Aceclofenac and Eudragit L100 e) Physical mixture of Aceclofenac and Eudragit S100

So for the formulations F13-F21, dissolution testing was performed by simulating conditions of the GI tract, i.e., 2, 1, 2 and remaining subsequent hours for the stomach, proximal part of small intestine, lower part of small intestine and terminal ileum at the media with pH 1.2, 6.5, 6.8 and 7.2, respectively.

Stability studies [14, 15]:

In the present study, stability studies were carried out for both at room temperature and accelerated stability conditions. The conditions for storing at room temperature were kept as 30±2 °C and 65±5% RH and for accelerated stability conditions were kept at 40±2 °C and 75±5% RH in a humidity chamber. At regular intervals of time (0,3 and 6 months) samples were withdrawn and were evaluated for weight variation, hardness, thickness, drug content and in-vitro release profile.

RESULTS AND DISCUSSION:

FTIR Studies:

Drug taken for the present study of formulation is Aceclofenac. It has got the peaks at 3306.75 cm^-1 (which indicates secondary amine O–H stretching or N–H stretching), 1721.48 cm^-1 (which indicates –C=O stretching), 1497.62 cm^-1 (which indicates aromatic –C=C stretching), and 1248.71 cm^-1 (which indicates –C–O stretching). These are the characteristic absorption peak of Aceclofenac. Whereas Eudragit L100 shows the peaks at 3421 cm^-1 (which indicates -OH stretching); 2904 cm^-1 (which indicates -OCH ₃ stretching) and 1705 cm ^-1 (which indicates - C=O stretching). Similarly, Eudragit S100 shows the peaks at 3423 cm^-1 (which indicates -OH stretching); 2905 cm^-1 (which indicates -OCH ₃ stretching) and 1713 cm ^-1 (which indicates - C=O stretching). The IR spectra of Aceclofenac with Eudragit L100 and Eudragit S100, did not reveals any extra peaks. Only the peaks which were present in drug and polymer were repeated in the physical mixture. Thus, it confirms the absence of chemical interactions between Aceclofenac and polymers used. IR curves obtained for pure drug and physical mixtures are shown in Figure 1.

DSC Studies:

In order to confirm the results of FTIR studies, DSC studies were also performed to understand the nature of the drug in the Aceclofenac mini-tablets. DSC curves obtained for pure drug and physical mixtures are shown in Figure 2. The DSC of Aceclofenac shows a sharp endothermic peak at 152.38°C. Whereas the thermograms of the physical mixtures of Aceclofenac+Eudragit L100 and Aceclofenac+Eudragit S100 did not show any significant shift in the endothermic peak as their peaks were found at 151.63 ⁰C and 152.79 ⁰C. Thus, it confirms that the optimized Aceclofenac mini-tablets formulation is free from any chemical reaction and can be used for its therapeutic purpose.

Figure 2: DSC spectra of (a) Pure drug Aceclofenac b) Physical mixture of Aceclofenac and Eudragit L100 c) Physical mixture of Aceclofenac and Eudragit S100

Evaluation of powder blend:

Powder blend ready for compression containing drug and various excipients were subjected for pre-compression parameters (Micromeritic properties) to study their flow properties and to achieve uniformity of tablet weight. The results of all the pre-compressional parameters are given Table 3. The angle of repose of all the batches was found to range between 23°.65’ to 24°.95’ which is lesser than 25 and thus the powder blend has excellent flow properties.

Table 3: Results of pre-compressional parameters for the prepared powder blend of all the formulations

Formulation code	Angle of repose (°) ± SD, n=3	Bulk density (gm/cc) ± SD, n=3	Tapped density (gm/cc) ± SD, n=3	Carr’s index (%) ± SD, n=3	Hausner’s ratio ± SD, n=3
F1	23°.80’±0.26	0.509±0.02	0.570±0.02	12.2±0.68	1.11±0.06
F2	23°.65’±0.25	0.511±0.03	0.571±0.01	10.5±0.64	1.11±0.09
F3	24°.89’±0.08	0.516±0.04	0.592±0.03	13.5±0.60	1.15±0.013
F4	23°.82’±0.19	0.523±0.05	0.605±0.01	13.3±0.14	1.15±0.12
F5	24°.87’±0.06	0.526±0.02	0.602±0.03	13.3±0.18	1.15±0.10
F6	23°.81’±0.20	0.536±0.01	0.625±0.04	14.5±0.25	1.16±0.12
F7	23°.83’±0.21	0.539±0.04	0.612±0.01	13.1±0.12	1.15±0.07
F8	24°.95’±0.11	0.541±0.03	0.623±0.02	12.9±0.27	1.14±0.05
F9	24°.90’±0.10	0.558±0.04	0.649±0.03	14±0.56	1.16±0.04
F10	23°.84’±0.26	0.560±0.05	0.632±0.04	11.1±0.45	1.12±0.04
F11	23°.82’±0.27	0.565±0.03	0.630±0.01	11.1±0.56	1.12±0.06
F12	23°.74’±0.25	0.568±0.04	0.621±0.01	9.6±0.42	1.10±0.05
F13	24°.21’±0.10	0.556±0.03	0.631±0.03	12.6±0.32	1.14±0.13
F14	24°.90’±0.04	0.548±0.01	0.641±0.01	15.6±0.26	1.18±0.04
F15	24°.37’±0.06	0.541±0.03	0.631±0.02	14.2±0.21	1.16±0.08
F16	23°.83’±0.27	0.558±0.06	0.619±0.01	9.8±0.39	1.10±0.09
F17	23°.87’±0.25	0.551±0.04	0.650±0.01	15.3±0.37	1.18±0.13
F18	23°.80’±0.26	0.561±0.05	0.673±0.03	16.4±0.35	1.19±0.10
F19	23°.79’±0.28	0.564±0.06	0.681±0.02	17.6±0.48	1.2±0.11
F20	24°.93’±0.07	0.549±0.04	0.612±0.01	11.4±0.41	1.12±0.08
F21	23°.86’±0.26	0.571±0.01	0.656±0.04	12.3±0.64	1.14±0.07

Table 4: Evaluation of Post-compression parameters of Aceclofenac mini-tablets

Formulation code	Weight variation (mg) (±SD), n=20	Hardness (kg/cm2) (±SD), n=6	Thickness (mm) (±SD), n=6	Friability (%) (±SD), n=6	% Drug content (±SD), n=3
F1	24±0.08	2.32±0.04	2.02±0.03	0.24±0.06	98.05±0.21
F2	23±0.16	2.33±0.05	2.04±0.05	0.26±0.03	98.08±0.22
F3	23±0.18	2.35±0.03	2.06±0.04	0.32±0.02	98.04±0.23
F4	23±0.14	2.40±0.04	2.01±0.11	0.28±0.05	98.05±0.24
F5	23±0.20	2.41±0.06	2.05±0.02	0.34±0.09	98.09±0.25
F6	24±0.03	2.47±0.14	2.05±0.05	0.31±0.06	98.02± 0.26
F7	24±0.07	2.33±0.12	2.06±0.03	0.25±0.05	99.01±0.23
F8	25±0.06	2.34±0.10	2.10±0.09	0.23±0.06	99.00±0.16
F9	24±0.15	2.35±0.09	2.09±0.10	0.22±0.04	98.10±0.15
F10	25±0.03	2.36±0.06	2.14±0.08	0.27±0.07	98.08±0.16
F11	24±0.09	2.41±0.03	2.12±0.09	0.26±0.08	99.02± 0.06
F12	25±0.13	2.43±0.04	2.13±0.07	0.31±0.09	99.00±0.15
F13	26±0.18	2.32±0.02	2.12±0.08	0.25±0.06	99.01±0.17
F14	27±0.07	2.34±0.04	2.13±0.07	0.31±0.07	98.10±0.18
F15	26±0.09	2.37±0.05	2.11±0.03	0.33±0.08	98.09±0.16
F16	25±0.17	2.42±0.09	2.11±0.01	0.38±0.07	99.00±0.18
F17	26±0.12	2.44±0.13	2.10±0.12	0.48±0.06	99.01±0.14
F18	25±0.17	2.46±0.13	2.12±0.11	0.46±0.06	99.01±0.09
F19	26±0.19	2.43±0.11	2.13±0.10	0.42±0.08	98.09±0.13
F20	27±0.01	2.45±0.12	2.11±0.09	0.51±0.05	98.09±0.12
F21	27±0.04	2.47±0.13	2.12±0.11	0.53±0.08	99.01±0.16

For all the batches of powder blend, the LBD and TBD were found to range between 0.509±0.02 to 0.568±0.04 and 0.570±0.02 to 0.681±0.02 gm/cc respectively. This indicates good packing capacity of the powder blend. The results of Carr’s consolidation index or compressibility index (%) for all the batches of the powder blend were found to be 9.6±0.42% and 17.6±0.48% respectively. Hausner ratio of all batches were found to be in the range between 1.11±0.06 to 1.19±0.10 which is lesser than 1.25 and thus indicates better flow properties.

Evaluation of post-compression parameters:

The results of all the post-compressional parameters are given Table 4. In the present study, the hardness of all the batches of mini-tablets were found to range between 2.32±0.04 kg/cm² and 2.47±0.13kg/cm² respectively indicating that they possessed sufficient mechanical strength. Tablet hardness is not an absolute indicator of strength. Another measure of tablets strength is friability. The friability of all the batches of mini-tablets was found to be in between 0.22±0.04 and 0.53±0.08 respectively. Conventional compressed tablets that loose less than 1 % of their weight are generally considered acceptable. In the present study, percent friability of all the batches was below 1 % limit as shown in the pharmacopoeia indicating that the friability is within the standard limit. It ensures that the Aceclofenac mini-tablets were mechanically stable. The weight variation test was performed according to the procedure given in the pharmacopoeia. The weight variation test was performed according to the procedure given in the pharmacopoeia. In a weight variation test, pharmacopoeial limit for the percentage deviation of tablets weighing 130 mg or less is ± 10 %. The average percentage deviation for all the batches of mini-tablets were found to be in between 23±0.14 mg and 27±0.07 mg respectively and it was found to be within the pharmacopoeial limits. The weight of all the batches of mini-tablets was found to be uniform with low standard deviation values indicating efficient mixing of drug and excipient. The mean thickness (n=6) was almost uniform for all the batches and values were found to be in between 2.01±0.11 mm and 2.14±0.08 mm respectively. The standard deviation values indicated that all the batches were within the range. The percentage drug content were found to be in between 98.04±0.23 % and 99.02±0.06 % of Aceclofenac for all the batches of the core mini-tablets indicating good content uniformity in both the batches. That indicates drug was uniformly distributed throughout the core mini-tablets.

In-vitro dissolution studies:

Effect of Eudragit L100 on in-vitro dissolution of aceclofenac:

The effect of Eudragit L100 on in-vitro dissolution of Aceclofenac mini-tablets was evaluated from 5 % to 60 % polymer content (F1 to F6). Mini-tablets formulations prepared with less than 20 % of Eudragit L100 release more than 10% of the drug in pH 1.2 at end of 2 hours. Whereas remaining Mini-tablets formulations prepared with more than 20 % of Eudragit L100 release less than 10 % of the drug in 0.1N HCl indicating adequate enteric effect. So, further dissolution studies in pH 6.5 and above were conducted for only formulations F3 to F6. It was found that these formulations release more than 50 % of the drug at pH 6.5 and 6.8 whereas more than 70 % of the drug in pH 7.4 within 30 minutes. This may be due to the fact that L100 dissolves at pH 6 and above. The release profile of formulations F1 to F6 is shown in figure 3a, 3b, 3c and 3d.

Effect of Eudragit S100 on in-vitro dissolution of aceclofenac:

The effect of Eudragit S100 on in-vitro dissolution of Aceclofenac mini-tablets was also evaluated from 5 % to 60 % polymer content (F7 to F12). Mini-tablets formulations prepared with less than 20 % of Eudragit S100 release more than 10% of the drug in pH 1.2 at end of 2 hours. Whereas remaining mini-tablets formulations prepared with more than 20 % of Eudragit S100 release less than 10% of the drug in 0.1N HCl indicating adequate enteric effect. So, further dissolution studies in pH 6.5 and above were conducted for only formulations F9 to F12. In formulations F9 to F12 less than 30% of Aceclofenac is released within 30 minutes in pH 6.5 and 6.8 buffer. For all formulations F9 to F12 the release is less than 40% in two hours. This may be due to the fact that Eudragit S-100 is insoluble at pH 6.5. Moreover, as the concentration of the S-100 increases the drug release decreases. In pH 7.2 more than 70% of Aceclofenac is released within 30 minutes except F12 which might be because of the higher concentration of Eudragit S-100 i.e 60%. The release profile of formulations F1 to F6 is shown in figure 3e, 3f, 3g and 3i.

Fig 3: Dissolution profile of a) Aceclofenac Eudragit L-100 mini-tablet in pH 1.2 b) Aceclofenac Eudragit L-100 mini tablet in pH 6.5 c) Aceclofenac Eudragit L-100 mini -tablet in pH 6.8 d) Aceclofenac Eudragit L-100 mini-tablet in pH 7.2 e) Aceclofenac Eudragit S-100 mini-tablet in pH 1.2 f) Aceclofenac Eudragit S-100 mini tablet in pH 6.5 g) Aceclofenac Eudragit S-100 mini-tablet in pH 6.8 h) Aceclofenac Eudragit S-100 mini-tablet in pH 7.2

Based on the above study, it was concluded that in order to target the release of the drug in a narrow time segment of 6 to 8 hours post dosing, a combination of L-100 and S-100 may prove beneficial. Thus, a full factorial 3² DOE was run in which three levels of L100 and S100 combination were evaluated. Initially, all formulations were evaluated for enteric effect by performing dissolution testing in pH 1.2 buffer (as shown in figure 4a). All formulations show adequate enteric effect in that none of the formulations release < 10% of the drug in 2 hrs in pH 1.2 (as shown in figure 4c).

The dissolution profile for all formulations was conducted using the novel in-situ pH change method in order to mimic the passage of the dosage form through in vivo system. The dissolution profile of Aceclofenac (Eudragit L-100+ S-100) in pH 1.2 at the end of 2hrs is represented in Figure 4b. All formulations release < 10% of the drug in 0.1N HCl indicating adequate enteric effect. The dissolution profile of Aceclofenac (Eudragit L-100+ S-100) at the end of 5.5hrs is represented in Figure 4d. Except for formulation F13 and F19, all other formulation release < 40% of the drug at 5.5 hours indicating that maximum concentration of drug can be targeted after 6 hours during the time of its greatest need. The reason for faster drug release in F13 and F19 may be due to the fact that Eudragit L-100 concentration is playing a more predominant role in drug release as compared to Eudragit S-100. The dissolution profile of Aceclofenac (Eudragit L-100+ S-100) at 6, 7 and 8 hours is represented in Figure 4e. All formulations containing high or medium levels of Eudragit L100 and low levels of Eudragit S-100 release the drug within a short period. Formulations containing higher levels of Eudragit S-100 show greater retardation of the drug release. However, > 70% drug release is observed in all formulations at the end of 8 hours of dissolution run by the in-situ pH change method. This indicates that the drug can be successfully targeted into the large intestine and colonic regions of the GIT by using combination of pH sensitive polymers Eudragit L100 and Eudragit S100.

Figure 4: a) Dissolution profile of Aceclofenac Eudragit L-100+ Eudragit S-100 matrix minitablets in pH 1.2 buffer b) Fig 16 : Dissolution profile for Aceclofenac 100 mg pulsatile release minitablets in situ pH change method (pH 1.2-pH6.5- pH6.8-pH7.2) c) Dissolution profile of Aceclofenac mini-tablets (Eudragit L-100+ S-100) in pH 1.2 at the end of 2hrs d) Dissolution profile of Aceclofenac mini-tablets (Eudragit L-100+ Eudragit S-100) in at the end of 5.5 hrs e) Dissolution profile of Aceclofenac mini-tablets (Eudragit L-100+ S-100) at the end of 6, 7 and 8 hrs.

DOE FOR ACECLOFENAC RELEASE:

The dissolution at 2 (D2), 5.5 (D5.5), 6 (D6) and 8 hours (D8) were considered as critical since they define the rate and extent of drug release. These values were fed into the DOE Pro XL software and the results of the DOE are given below:

Table 5: DOE Design sheet for the dissolution at 2nd hour

Factor	A	B	%DR- 2hr
Row #	E-L100	E-S100	Y1	Y bar
1	10	10	7.8	7.8
2	10	20	5.08	5.08
3	10	30	4.18	4.18
4	20	10	4.28	4.28
5	20	20	4.5	4.5
6	20	30	3.57	3.57
7	30	10	2.06	2.06
8	30	20	3.17	3.17
9	30	30	3.86	3.86

Table 6: DOE Design sheet for the dissolution at 5.5 hour

Factor	A	B	%DR- 5.5 hr
Row #	E-L100	E-S100	Y1	Y bar
1	10	10	78.09	78.09
2	10	20	23.78	23.78
3	10	30	13.64	13.64
4	20	10	39.69	39.69
5	20	20	20.08	20.08
6	20	30	13.86	13.86
7	30	10	68.17	68.17
8	30	20	12.47	12.47
9	30	30	8.13	8.13

Table 7: DOE Design sheet for the dissolution at 6 hour

Factor	A	B	%DR- 6hr
Row #	E-L100	E-S100	Y1	Y bar
1	10	10	90.56	90.56
2	10	20	85.43	85.43
3	10	30	78.89	78.89
4	20	10	88.57	88.57
5	20	20	80.76	80.76
6	20	30	50.76	50.76
7	30	10	84.09	84.09
8	30	20	55.57	55.57
9	30	30	55.78	55.78

Table 8: DOE Design sheet for the dissolution at 8 hour

Factor	A	B	%DR-8hr
Row #	E-L100	E-S100	Y1	Y bar
1	10	10	96.23	96.23
2	10	20	90.24	90.24
3	10	30	94.56	94.56
4	20	10	98.07	98.07
5	20	20	90.83	90.83
6	20	30	78.87	78.87
7	30	10	95.36	95.36
8	30	20	78.9	78.9
9	30	30	78.65	78.65

The surface response graphs as shown above defined a design space for all the two polymers within which when the mini-tablets are fabricated, the TPP will always be achieved. The focus of this work was to optimize the Aceclofenac mini-tablets using Design of Experiment.

Figure 5: Y-Hat surface plot for Eudragit L100 Vs Eudragit S100 for a) 2 hrs (D2) b) 5.5 hrs (D5.5) c) 6 hrs (D6) d) 8 hrs (D8)

Table 9: Optimized range for the combination of two polymers

Polymer	Low Level	High Level
Eudragit L-100	21	24
Eudragit S-100	16.5	21

On finding the two Critical Formulation Ingredients or parameters, a 3² experimental design using DOE was run to identify the interaction between these parameters. A strong correlation was found between these parameters and a design space as shown in Table 9 within which the formulation passes the acceptance criteria for the release of drug was determined.

Based on the above table, a pulsatile release mini-tablets of Aceclofenac can be successfully developed when a combination of Eudragit L100 and Eudragit S100 polymers are used in the range. The product is designed to release < 40% the drug for nearly 5.5 to 6. hours post dosing but is designed to release > 80% of the drug within 6to 8 hours post dosing ensuring early morning relief from stiffness to the arthritic patients. Using this design space, three batches were fabricated using the concentration of polymers between these low and high level range and dissolution profile is shown in Table 10 and graphically represented in Figure 6. The dissolution profile of all these three formulations was found to be in the TPP range. These batches were also tested for room temperature and accelerated stability studies.

Figure 6: Dissolution profile of optimized formulations

Table 10: Dissolution results of optimised formulation

	pH	Time	TPP	F22	F23	F24
Represents the pH of stomach	1.2	0		0±0.00	0±0.00	0±0.00
		2	Not more than 10%	4.04±0.23	3.98±0.31	3.56±0.32
Represents the pH of duodenum	6.5	3		14.56±0.41	13.45±0.41	13.23±0.57
Represents the pH of jejenum	6.8	4		16.15±0.51	15.89±0.52	14.67±0.81
		5		20.69±0.46	19.96±0.58	18.97±0.43
Represents the pH of terminal ileum	7.2	5.5	Not more than 40%	35.40±0.75	34.85±0.68	34.56±0.72
		6.0	75-85%	83.37±0.58	82.21±0.57	81.65±0.48
		7		91.59±0.61	90.98±0.71	92.23±0.47
		8	More than 85%	97.85±0.35	95.90±0.46	97.65±0.36
		10		99.10±0.62	98.45±0.52	99.06±0.31
		12		100±0.54	99.56±0.72	99.97±0.45

Table 11: Stability studies: Appearance and drug content for optimized formulations

Parameters		Storage conditions and time (months)
		Initial results	Room temperature 30±2 °C and 65±5% RH		Accelerated stability 40±2 °C and 75±5% RH
		0	3	6	3	6
Appearance		White circular mini-tablets	No change in appearance	No change in appearance	No change in appearance	No change in appearance
Drug content (%)	F22	98.51± 0.10 %	98.38± 0.15 %	98.10± 0.31 %	98.46± 0.12 %	98.13± 0.36 %
	F23	99.09± 0.09 %	98.98± 0.12 %	98.85± 0.04 %	99.03± 0.15 %	98.95± 0.28 %
	F24	99.71± 0.56 %	99.59± 0.41 %	99.26± 0.16 %	99.64± 0.24 %	99.09± 0.16 %

Table 12: Stability studies: Dissolution Profile (At room temperature 30±2 °C and 65±5% RH)

Time (Hrs)

Specificaion (TPP)

% Cumulative Drug Released (F22)

% Cumulative Drug Released (F23)

% Cumulative Drug Released (F24)

Initial Results

3 Month

6 Month

Initial Results

3 Month

6 Month

Initial Results

3 Months

6 Months

0

0

0±0.00

0±0.00

0±0.00

0±0.00

0±0.00

0±0.00

0±0.00

0±0.00

0±0.00

2

Not more than 10%

4.04± 0.22

3.81± 0.19

3.44± 0.56

3.98± 0.34

3.73± 0.45

3.32± 0.34

3.56± 0.67

3.35± 0.12

2.95± 0.22

5.5

Not more than 40%

35.40± 0.46

35.01± 0.45

34.61± 0.86

34.85± 0.46

34.61± 0.45

34.24± 0.56

34.56± 0.56

34.38± 0.34

32.97± 0.67

6

75-85%

83.37± 0.43

83.12± 0.59

82.72± 0.67

82.21± 0.56

80.93± 0.12

80.51± 0.23

81.65± 0.45

81.43± 0.76

80.03± 0.67

8

More than 85%

97.85± 0.97

97.60± 0.66

97.21± 0.45

95.90± 0.76

95.65± 0.50

95.25± 0.41

97.65± 0.81

96.41± 0.31

96.01± 0.39

Table 13: Stability studies: Dissolution Profile (At Accelerated stability conditions 40±2 °C and 75±5% RH)

Time (Hrs)

Specification (TPP)

% Cumulative Drug Released (F22)

% Cumulative Drug Released (F23)

% Cumulative Drug Released (F24)

Initial Results

3 Month

6 Month

Initial Results

3 Month

6 Month

Initial Results

3 Months

6 Months

0

0

0± 0.00

0± 0.00

0± 0.00

0± 0.00

0± 0.00

0± 0.00

0± 0.00

0± 0.00

0± 0.00

2

Not more than 10%

4.04± 0.22

3.95± 0.14

3.65± 0.37

3.98± 0.34

3.88± 0.13

3.51± 0.26

3.56± 0.67

3.46± 0.19

3.11± 0.12

5.5

Not more than 40%

35.40± 0.46

35.31± 0.27

35.01± 0.13

34.85± 0.46

34.73± 0.42

34.41± 0.12

34.56± 0.56

34.41± 0.24

34.09± 0.46

6

75-85%

83.37± 0.43

83.21± 0.35

82.91± 0.21

82.21± 0.56

82.14± 0.56

81.86± 0.51

81.65± 0.45

81.53± 0.41

81.27± 0.31

8

More than 85%

97.85± 0.97

97.71± 0.46

97.42± 0.67

95.90± 0.76

95.79± 0.61

95.31± 0.41

97.65± 0.81

97.51± 0.35

97.19± 0.53

Results of stability testing: Formulation batches F22, F23 and F24 was packed in 90 ml HDPE containers (30s count/container) and charged at both room temperature (30±2 °C and 65±5% RH) and accelerated stability conditions (40±2 °C and 75±5% RH) in a humidity chamber. The mini-tablets were evaluated for assay and dissolution profile testing at 0, 3 and 6 months as per ICH guidelines. The results are given in Tables 11, 12 and 13. The data for stability studies revealed that no considerable differences in drug content and dissolution rates were observed. Thus, it was concluded that in order to successfully develop Aceclofenac mini-tablet s with a pre-determined target dissolution profile over 12 hours, surface response methodology provides an excellent tools for optimization of polymer concentration when a combination of polymers is used. The design space as defined by the above experiments is within 37.5 to 45 range of the total polymer concentration.

CONCLUSION:

It can be concluded that the surface response curves defined a design space for all the three polymers within which when the mini-tablets are fabricated, the TPP will always be achieved. Thus, it was concluded that in order to successfully develop Aceclofenac mini-tablets with a pre-determined target dissolution profile over 12 hours, surface response methodology provides an excellent tools for optimization of polymer concentration when a combination of polymers is used. The design space as defined by the above experiments is within 37.5 to 45 range of the total polymer concentration.

ACKNOWLEDGMENTS:

Authors thanks to IPS Institute, Hyderabad for providing a gift sample of Aceclofenac. The authors are also thankful to Bhaskar Pharmacy College, R.R. District, Hyderabad and IPS Institute, Hyderabad for providing the research lab facilities to carry out this research work. The authors are very much thankful to the Chairman of JB group of Educational Institutions Sri. J. Bhaskar Rao Garu for his constant help, support and encouragement to the academics generally and research particularly.

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Received on 13.03.2014 Accepted on 20.04.2014

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Asian J. Pharm. Tech. 2014; Vol. 4: Issue 2, Pg 74-82