Optimization of Atenolol Core Tablet CHAPTER 5: OPTIMIZATION OF FORMULATION OF ATENOLOL CORE TABLETS

CHAPTER 5: OPTIMIZATION OF FORMULATION OF ATENOLOL CORE TABLETS 5.1. AIM OF THE STUDY The pulsatile type press coated colon targeted atenolol tablet release drug after 6 hr lag time. The compression coated tablet has two parts, internal core tablet and surrounding coat. For the preparation of pulsatile type press coated tablet of atenolol, first step is to prepare fast disintegrating core tablet of atenolol, which release drug within a shorter period of time after a lag time. Fast disintegrating tablets were prepared by addition of superdisintegrant. The aim of this study is to optimize the formulation of core tablets of atenolol, which give faster rate of drug release. So, the optimized core tablets of atenolol are used for preparation of press coated pulsatile tablets. 5.2. STATISTICAL OPTIMIZATION OF FORMULATION OF ATENOLOL CORE TABLETS A 3 2 randomized full factorial design and optimization process was investigated to find the utility in the optimization of formulation of core tablets of atenolol. In this design, two factors were evaluated, each at three levels, and experimental trials were performed at all nine possible combinations. This design is suitable for exploring linear response surface and constructing polynomial model incorporating polynomial terms used to evaluate the response. Y = b0 + b1a+b2b.... (1) Where, Y is the dependent variables, b0 is the arithmetic mean response of the nine runs, b1 is the estimated coefficient for the factor A and b2 is the estimated coefficient for the factor B. The main effects (A and B) represent the average result of changing one factor at a time from its low to high value. The amount of superdisintegrant (A) and amount of dry binder (B) in core formulation were selected as independent variables. The times required for 85% (T85%) drug Rajesh A. Keraliya 107

dissolution were selected as dependent variable. The independent variables with their levels are described in the table 11, while experimental design with corresponding formulation outline in table 12. Table 11: Independent variables with their levels Independent Variable Levels Low Medium High -1 0 +1 A: Sodium starch glycolate (mg) 2.5 5 7.5 B: Amount of polyvinyl pyrrolidone (mg) 5 10 15 Table 12 described the formulations prepared for 3 2 randomized full factorial design to optimize the formulation of core tablets of atenolol with the following goals: (1) Amount of SSG : 2.5 to 7.5 mg (2) Amount of PVP K30: 5 to 15 mg (3) T85% = 2 min Table 12: Formulation design layout for 3 2 factorial design Formulation code Independent variables coded value Independent variables actual value Factor 1 (A) Factor 2 (B) Factor 1 (A) Factor 2 (B) AT1-1 -1 2.50 5.00 AT2 0-1 5.00 5.00 AT3 +1-1 7.50 5.00 AT4-1 0 2.50 10.00 AT5 0 0 5.00 10.00 AT6 +1 0 7.50 10.00 AT7-1 +1 2.50 15.00 AT8 0 +1 5.00 15.00 AT9 +1 +1 7.50 15.00 Where, A = Amount of sodium starch glycolate (mg) and B = Amount of polyvinyl pyrrolidone (mg) Rajesh A. Keraliya 108

5.3. PREPARATION OF ATENOLOL CORE TABLETS The core tablets of atenolol were prepared by direct compression method. Atenolol core tablet was formulated using various amount of polyvinyl pyrrolidone (PVP K30) as dry binder and sodium starch glycolate as superdisintegrant as describe in table 13. An accurately weighed quantity of atenolol, microcrystalline cellulose, polyvinyl pyrroloide (PVP K30) and sodium starch glycolate pass through 40# and mix in double cone blender for 15 min. Add talc (2% w/w) (40#) into blend and mix in double cone blender for 10 min. Add magnesium stearate (1% w/w) (40#) into blend and mix in double cone blender for 5 min. The resultant powder mixtures were compressed into tablets (average tablet weight = 80 mg) by 6 mm standard concave plain punches using rotary tabletting machine (Hardik Engineering Works, Ahmedabad, India). The prepared atenolol core tablets were tested for weight variation, hardness, thickness, drug content, disintegration time, friability and in vitro dissolution study (Sawada et al., 2003, Mayur et al., 2009, Gang et al., 2004). Table 13: Formulations of atenolol core tablets Ingredients (mg) AT1 AT2 AT3 AT4 AT5 AT6 AT7 AT8 AT9 Atenolol 45 45 45 45 45 45 45 45 45 Sodium Starch glycolate (SSG) 2.5 5 7.5 2.5 5 7.5 2.5 5 7.5 Polyvinyl pyrrolidone (PVP K30) 5 5 5 10 10 10 15 15 15 Microcrystalline cellulose (MCC) 25.1 22.6 20.1 20.1 17.6 15.1 15.1 12.6 10.1 Talc 1.6 1.6 1.6 1.6 1.6 1.6 1.6 1.6 1.6 Mg stearate 0.8 0.8 0.8 0.8 0.8 0.8 0.8 0.8 0.8 Total wt. 80 80 80 80 80 80 80 80 80 5.4. EVALUATION OF ATENOLOL CORE TABLETS 5.4.1. Spectrophotometric estimation of atenolol Atenolol was estimated by UV visible spectroscopy. Spectrophotometric estimation of atenolol was carried out in triplicates methanol and phosphate buffer ph 7.4. Rajesh A. Keraliya 109

Preparation of standard stock solution in methanol and phosphate buffer ph 7.4 Accurately weighed 100 mg of atenolol was placed in 100 ml volumetric flask and dissolved in 100 ml of methanol and phosphate buffer ph 7.4. From this solution, 10 ml solution was withdrawn and further diluted to 100 ml with methanol and phosphate buffer ph 7.4 to yield the standard stock solution of atenolol (100 µg/ml). Construction of calibration curve in methanol and phosphate buffer ph 7.4 From the stock solution, 5, 10, 15, 20, 25 and 30 ml were withdrawn and diluted to 100 ml with methanol to yield concentration of 5, 10, 15, 20, 25 and 30 g/ml respectively. For phosphate buffer ph 7.4, 2.5, 5, 10, 15, 20, 25, 30 and 35 ml of stock solution were withdrawn and dilute to 100 ml with phosphate buffer ph 7.4 to yield concentration of 2.5, 5, 10, 15, 20, 25, 30 and 35 g/ml respectively. Absorbance of each solution was measured at 225 nm using UV visible spectrophotometer (Thermo Scientific Evolution 201). Samples were analyzed in triplicate and the average values were used for plotting the graph of absorbance versus concentration ( g/ml). Regression analysis was done on each beer s plot using Microsoft excel. 5.4.2. Drug-Excipient compatibility study Fourier transform infrared spectroscopy The FTIR spectra of pure sample powder of atenolol and powder of atenolol core tablet were recorded on a FT-IR spectrophotometer (Shimadzu, FTIR-8400S), in the wavelength region of 4000 400 cm -1. Samples (about 1% w/w) were mixed with KBr powder and suitable amount of sample was placed in sample holder. The sample holder was placed in the light path and the spectrum was obtained. Differential Scanning Calorimetry (DSC) A differential scanning calorimeter (DSC-60, shimadzu corporation, Japan) was used to monitor the thermal events during heating. The DSC was calibrated by the melting points of indium (156.6±0.2 0 C) and zinc (419.5±0.3 0 C) standards. Samples of pure sample powder of atenolol and powder of atenolol core tablet weighing 2 3 mg were placed in open aluminium pans and heated from 50 to 300 0 C at a rate of 20 0 C per min. Nitrogen Rajesh A. Keraliya 110

was used as a purge gas at a flux rate of 50 ml/min. The onsets of the melting points were calculated by the software (Pyris, Perkin-Elmer). 5.4.3. Evaluation of flow property of powder blend Angle of Response For characterizing the flowability, the angle of response was determined by pouring the powder blend used for preparation of atenolol core tablets and atenolol press coated tablets through a funnel. Height (h) and radius (r) of the powder cone were measured to calculate the angle of response as tan α = h/r. A small value for represents a good flowing powder. Carr s Consolidation Index a) Bulk Density The bulk density, as a measure used to describe packing of powder, was determined by transferring the accurately weighed sample of powder mixture to a graduated cylinder with the aid of a funnel. The initial volume was noted. Ratio of weight of the sample to the volume it occupied was calculated. Bulk Density = Mass of powder / Bulk volume.(2) b) Tapped Density Weighed sample of powder mixture was transferred to a graduated cylinder and was tapped for a fixed time or for a fixed number of taps (100). The tapped density was determined by using the following formula: Tapped Density = Mass of powder / Tapped volume.(3) Based on the apparent bulk density and the tapped density, the percentage compressibility of the powder mixture was determined by the following formula. Carr s index = {(Tapped density- Bulk density) / Tapped density}* 100 (4) Hausner s Ratio Hausner ratio is an indirect index of ease of measuring the powder flow. It was calculated by the following formula: Rajesh A. Keraliya 111

Hausner s ratio = Tapped density / Bulk density. (5) 5.4.4. Post compression evaluation of atenolol core tablets Weight Variation Twenty tablets from each batch were individually weighed using electronic digital balance (Shimadzu BL 220 H) and average weight was calculated. Individual weights of the tablets were compared with the average weight according to the official method in Indian Pharmacopoeia, 2007 (Fukui et al., 2000, Gazzaniga et al., 1994). Hardness Six tablets from each batch were selected and tested for tablet hardness using Monsanto hardness tester. The tablet was placed in contact between the plungers and the handle was pressed, the force of the fracture that causes the tablet to break was recorded (Krishnaiah et al., 1998). Thickness The thickness of ten tablets from each batch was determined using vernier calipers as per Indian Pharmacopoeia, 2007 (Madhusudan and Vishal, 2001). Friability The friability of the twenty tablets from each batch was determined using Roche friabilator (Indosati Scientific Lab. Equipments) (Mastiholimath et al., 2007, Matsuo et al., 1995). This device subjects the tablets to the combined effect of abrasions and shock in a plastic chamber revolving at 25 rpm and dropping the tablets at a height of 6 inches in each revolution. A pre-weighed sample (20 tablets) was placed in the friabilator and is subjected to 100 revolutions. Tablets were dedusted and reweighed. The % friability (F) was calculated using following formula: F = (W1-W2 / W1) 100.. (6) Where, W1 is the initial weight of the sample of twenty tablets before the test W2 is the weight of the tablet after the test Rajesh A. Keraliya 112

Disintegration test Six tablets of each batch were placed in the each glass tube of disintegration test apparatus (Indosati Scientific Lab. Equipments) containing 900 ml of water maintained at a temperature of 37±1 0 C and disintegration time of core tablets was determined (Shweta et al., 2008, Gazzaniga et al., 2006). The study was carried out in triplicates. Drug content For determination of drug content, ten tablets were crushed into powder and powder equivalent to 45 mg of atenolol was weighed and dissolved in methanol then filtered through syringe filter (Axiva SFCA25X, 0.45µm). Solution was analyzed for Atenolol content by spectrophotometrically by UV spectrophotometer (Thermo Scientific Evolution 201) at wavelength of 225 nm using methanol as blank (Swati et al., 2010). Wetting time To measure wetting time of tablet, a piece of tissue paper was folded twice and placed in a small petridish of 8.5 cm diameter. 10 ml of distilled water containing methylene blue, a water soluble dye, is added to petridish. A tablet was kept on the paper and the time required for water to reach upper surface of the tablet at room temperature is noted as a wetting time (Kalpesh et al., 2011). The study was carried out in triplicates. Water absorption ratio A piece of tissue paper folded twice was placed in a small petridish of 8.5 cm diameter containing 6 ml of distilled water. A tablet was put on the paper and the time required for complete wetting of the tablet was measured. The wetting tablet was then weighed. Water absorption ratio R was determined using the equation (Bhupendra and Dipesh, 2010): Water absorption ratio (R) = (W2 W1)/ W1 *100.(7) Where, W1 = weight of tablet before water absorption and W2 = weight of tablet after water absorption. In vitro drug release study of atenolol core tablets In vitro dissolution studies of atenolol core tablets were carried out using USP Type II dissolution apparatus (Electrolab, TDT-08L) using 900 ml of phosphate buffer ph 7.4 as Rajesh A. Keraliya 113

a dissolution media at a temperature of 37±1 0 C at 75 rpm. At regular time intervals, 10 ml of sample was withdrawn and same amount replaced by fresh medium. Samples were suitably diluted and filtered through syringe filter (Axiva SFCA25X, 0.45µm). Drug amount released was analyzed spectrophotometrically by UV spectrophotometer (Thermo Scientific Evolution 201) at wavelength of 225 nm. All studies were carried out in triplicates (Swati et al., 2010). The study was carried out in triplicates. 5.4.5. Stability study The optimized formulations of atenolol core tablets were subjected for accelerated stability studies according to ICH guidelines (40 ± 2 0 C and 75 ± 5% RH) for a period of 6 months in a stability chamber. The optimized formulations of atenolol core tablets were placed in vials and hermetically closed with bromobutyl rubber plugs, sealed with aluminum caps and placed in stability chamber. The samples were withdrawn at initial, 1, 2, 3 and 6 month and evaluated for the drug content, hardness, disintegration time and in vitro dissolution. The study was carried out in triplicates. 5.5. RESULTS AND DISCUSSION 5.5.1. Spectrophotometric estimation of Atenolol Spectrophotometric estimation of Atenolol in methanol Table 14: Spectrophotometric analysis of atenolol in methanol Conc. Absorbance Average Standard (µg/ml) Set 1 Set 2 Set 3 Absorbance Deviation 2.5 0.116 0.115 0.115 0.115 0.004 5 0.207 0.205 0.204 0.205 0.005 10 0.315 0.313 0.313 0.314 0.003 15 0.443 0.440 0.441 0.441 0.002 20 0.558 0.553 0.555 0.555 0.004 25 0.663 0.658 0.660 0.660 0.002 30 0.795 0.793 0.793 0.794 0.003 35 0.915 0.913 0.916 0.915 0.004 Rajesh A. Keraliya 114

Average Abs. Ph.D Thesis Atenolol exhibited its maximum absorption at 225 nm and obeyed Beer s law in the range of 2.5-35 μg/ml. Linear regression of absorbance on concentration gave equation y = 0.024x + 0.071 with a correlation coefficient of 0.998. So, calibration curve of atenolol in methanol showed in figure 27 was linear in concentration range of 2.5-35 μg/ml. 1.000 0.900 0.800 0.700 0.600 0.500 0.400 0.300 0.200 0.100 0.000 Calibration curve of atenolol methanol y = 0.024x + 0.0717 R² = 0.9988 0 5 10 15 20 25 30 35 40 Conc. (µg/ml) Figure 27: Calibration curve of atenolol in methanol Figure 28: Spectrophotometric images showing λmax of atenolol in methanol Rajesh A. Keraliya 115

Average Abs. Ph.D Thesis Spectrophotometric estimation of atenolol in Phosphate buffer ph 7.4 Table 15: Spectrophotometric analysis of atenolol in phosphate buffer ph 7.4 Conc. Absorbance Average Standard (µg/ml) Set 1 Set 2 Set 3 Absorbance Deviation 2.5 0.11 0.114 0.113 0.112 0.002 5 0.212 0.209 0.21 0.21 0.002 10 0.312 0.311 0.309 0.311 0.002 15 0.44 0.438 0.437 0.438 0.001 20 0.551 0.55 0.549 0.550 0.006 25 0.66 0.65 0.662 0.657 0.003 30 0.781 0.783 0.778 0.781 0.001 35 0.897 0.895 0.895 0.896 0.002 Atenolol exhibited its maximum absorption at 225 nm and obeyed Beer s law in the range of 2.5-35 μg/ml. Linear regression of absorbance on concentration gave equation y = 0.023x + 0.075 with a correlation coefficient of 0.998. So, calibration curve of atenolol in phosphate buffer ph 7.4 showed in figure 29 was linear in concentration range of 2.5-35 μg/ml. Calibration curve of atenolol in phosphate buffer ph 7.4 1.0 0.9 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0.0 y = 0.0235x + 0.0753 R² = 0.9982 0 5 10 15 20 25 30 35 40 Conc. (µg/ml) Figure 29: Calibration curve of atenolol in phosphate buffer ph 7.4 Rajesh A. Keraliya 116

Figure 30: Spectrophotometric image showing λmax of atenolol in phosphate buffer ph 7.4 5.5.2. Drug-Excipient compatibility study Fourier transform infrared spectroscopy Fourier transform infrared spectroscopy was used to analyze of pure sample powder of atenolol and powder of atenolol core tablet. Figure 31 showed that FTIR spectras of all samples were identical and the main absorption bands of atenolol appeared in all the spectra. Absorption band for N-H stretching of CO-NH2 group of atenolol appeared around 3340 and 3160 cm 1 in the both spectra. The absorption band for -C=O (amide I) and N-C=O (amide II) stretching of atenolol located at 1625 cm 1 and 1500 cm 1 in spectra of pure atenolol drug powder, and these were also appear and not shifted in the FTIR spectra of powder of atenolol core tablet. All spectra showed =C-H stretching of alkane group of atenolol around 2940 cm 1. Similarly, the H2N-C=O stretching of atenolol located at 1400 cm 1 was appeared both in both spectra. Isopropyl group of atenolol showed a sharp peak in all spectra around 1385 cm 1 and 1170 cm 1. Arylether of atenolol structure give the peak at 1390 cm 1 and 1235 cm 1 in spectra of pure atenolol drug powder, and these were also appear in the FTIR spectra of powder of atenolol core tablet (Klaus et al., 2005). The FTIR spectra of the tested samples showed Rajesh A. Keraliya 117

the prominent characterizing peaks of pure atenolol which confirmed that no chemical modification of the drug had been taken place and indicated that there is no chemical interaction occurred between drug and excipients at the molecular level. Figure 31: FTIR spectra of: pure sample powder of atenolol (A) and powder of atenolol core tablet (B) Differential Scanning Calorimetry (DSC) DSC thermographs of pure sample powder of atenolol and powder of atenolol core tablet showed a sharp exothermic peak (Tm) at 156.11 0 C and 156.21 0 C respectively, which corresponding to melting point of atenolol (154 C to 156 C) (Klaus et al., 2005, Gurpreet et al., 2009). Melting exotherm not appreciably change in powder of atenolol core tablet as compared to atenolol pure sample. This observation confirmed the absence of chemical interaction of drug with excipients of core tablet, further supporting the results of IR spectroscopy. The DSC results of pure sample powder of atenolol and powder of atenolol core tablet showed in figure 32. Rajesh A. Keraliya 118

Figure 32: DSC thermographs of: pure sample powder of atenolol (A) and powder of atenolol core tablet (B) 5.5.3. Flow property study of powder blend The angle of repose, hausner s ratio and carr s index of powder blend used for atenolol core tablets were ranged from 28.10 O ± 0.65 to 29.80 O ± 0.50, 1.144 ± 0.13 to 1.194 ± 0.14, and 12.65 ± 0.41 % to 16.27 ± 0.44 % respectively as shown in table 16. The results of indicated that powder blend has good flow property with good compressibility and suitable for direct compression method. 5.5.4. Post compression evaluation of atenolol core tablets As shown in table 17 all atenolol core tablets had good mechanical strength, showed hardness in range from 3.0 to 4.5 Kg/cm 2 and friability was range from 0.05 ± 0.05 to 0.17 ± 0.07. Friability is less than 1% which indicated that tablets had good mechanical resistance. All atenolol core tablets showed drug content above 99.65 %. In weight Rajesh A. Keraliya 119

variation test, none of tablets showed more than 10 % weight variation from average weight. So, all formulations pass the weight variation test as per IP. Tablet thickness varied from 3.19 to 3.20 mm. Table 16: Flow property study for powder blend of atenolol core tablets Formulation Code Bulk Density (g/cm 3 ) (Avg. ± SD) Tapped Density (g/cm 3 ) (Avg. ± SD) Carr s Index (%) (Avg. ± SD) Hausner s Ratio (HR) (Avg. ± SD) Angle of Repose (Ɵ) (Avg. ± SD) AT1 0.282 ± 0.02 0.331 ± 0.03 14.80 ± 0.65 1.173 ± 0.12 29.67 O ± 0.25 AT2 0.280 ± 0.03 0.33 ± 0.04 15.15 ± 0.65 1.178 ± 0.12 29.74 O ± 0.40 AT3 0.283 ± 0.04 0.338 ± 0.03 16.27 ± 0.44 1.194 ± 0.14 29.80 O ± 0.50 AT4 0.278 ± 0.05 0.327 ± 0.02 14.98 ± 0.59 1.176 ± 0.14 29.32 O ± 0.36 AT5 0.281 ± 0.04 0.328 ± 0.03 14.32 ± 0.54 1.167 ± 0.15 29.20 O ± 0.55 AT6 0.279 ± 0.03 0.325 ± 0.03 14.15 ± 0.35 1.164 ± 0.13 29.09 O ± 0.35 AT7 0.283 ± 0.03 0.324 ± 0.04 12.65 ± 0.41 1.144 ± 0.13 28.10 O ± 0.65 AT8 0.282 ± 0.05 0.326 ± 0.03 13.49 ± 0.60 1.156 ± 0.10 28.76 O ± 0.47 AT9 0.279 ± 0.04 0.326 ± 0.04 14.41 ± 0.48 1.168 ± 0.15 28.96 O ± 0.34 Table 17: Post compression parameters of atenolol core tablets Formulation Code Hardness (Kg/cm 2 ) (Avg. ± SD) Friability (%) (Avg. ± SD) Drug content (%) (Avg. ± SD) Weight variation (mg) (Avg. ± SD) Tablet Thickness (mm) (Avg. ± SD) AT1 3.25 ± 0.25 0.11 ± 0.05 99.60 ± 1.5 79.77 ± 1.50 3.20 ± 0.06 AT2 3.25 ± 0.15 0.12 ± 0.05 99.97 ± 1.3 79.57 ± 2.57 3.20 ± 0.05 AT3 3.0 ± 0.3 0.17 ± 0.07 100.97 ±1.6 80.75 ± 1.75 3.19 ± 0.01 AT4 3.75 ± 0.5 0.08 ± 0.06 99.55 ± 1.5 79.55 ± 1.65 3.20 ± 0.03 AT5 3.5 ± 0.15 0.10 ± 0.07 100.85 ± 1.8 80.40 ± 2.55 3.20 ± 0.05 AT6 3.25 ± 0.15 0.12 ± 0.05 99.95 ± 1.6 79.30 ± 1.65 3.20 ± 0.03 AT7 4.5 ± 0.4 0.05 ± 0.05 100.75 ± 1.4 80.60 ± 2.25 3.20 ± 0.04 AT8 4.25 ± 0.5 0.07 ± 0.03 99.85 ± 1.7 79.65 ± 2.75 3.20 ± 0.05 AT9 4.25 ± 0.3 0.008 ± 0.08 99.98 ± 1.6 79.57 ± 1.25 3.19 ± 0.02 Rajesh A. Keraliya 120

Superdisintegrants are added to oral solid dosage formulations to facilitate disintegration. Commonly used superdisintegrants such as crospovidone, croscarmellose sodium, and sodium starch glycolate are highly efficient at low concentration levels in the tablet formulation at facilitating the rate and extent of tablet disintegration. After completion of disintegration study, it was found that tablets prepared with sodium starch glycolate, disintegrate by rapid uptake of water, followed by rapid and enormous swelling. From table 18, formulation with 7.5 mg sodium starch glycolate showed a remarkable increase in disintegration time as compared to formulation containing 2.5 and 5 mg SSG. It was observed that sodium starch glycolate is effective at 5%. Disintegration time of tablets decreased from 39 second to 28 second as the amount of SSG was increased from 2.5 mg to 5 mg respectively in AT1 and AT2 formulation. While, the increase of the amount of sodium starch glycolate from 5 mg to 7.5 mg, the disintegration time was decreased as shown in table 18. The mechanism of disintegration of sodium starch glycolate is swelling. In the beginning it swells very fast and later on it swells gradually, probably due to confinement of the tablet and also due to viscosity change of the penetrating liquid. This exceptional behavior could also be due to the higher concentration of sodium starch glycolate which may act as a binder instead of swelling which causes gelling. Thus, causing a viscous barrier and so the disintegration time increases (Swati et al., 2010, Mallikarjuna et al., 2008). These results also supported by the water absorption study. The water uptake by the tablet is facilitated by the sodium starch glycolate, while the tablet disintegration is facilitated by the swelling force exhibited by sodium starch glycolate at their optimum concentration (Bhupendra and Dipesh, 2010). So, as the amount of sodium starch glycolate increased, the water absorption ratio increased up to optimum level of 5 mg SSG. But, at high amount 7.5 mg of SSG, water absorption ratio decreased, this may be due to at the higher concentration of sodium starch glycolate which may act as a binder instead of swelling. Formulations AT1, AT2 and AT3 showed 42.25 ± 3.85, 58.75 ± 4.57 and 54.60 ± 5.85 water absorption ratio respectively. Wetting was closely related to the inner structure of the tablets and the hydrophilicity of the excipients. SSG shows its disintegrant effect by the mechanism of swelling (Shailendra et al., 2009). It is interesting to note that wetting times decreased with increase in the level of sodium starch glycolate from 2.5 mg to 5 mg in the tablets. It was observed that formulations AT2 showed lower wetting time 20 sec., while AT1 showed wetting time 31 Rajesh A. Keraliya 121

sec. But formulations with higher level of sodium starch glycolate (7.5 mg), showed high wetting time. AT3, AT6 and AT9 containing high level of sodium starch glycolate had higher water absorption ratio and take more time for wetting of tablets (Table 18). When higher percentage of PVP K30 was used, higher binding between granules is expected in the tablets and tablet became harder, so, an increase in the amount of PVP K30 in the formulation lead to increase in hardness, disintegration time, wetting time, and decrease water absorption ratio and friability as shown in table 17 and 18 (Vineet et al., 2010). Table 18: Disintegration time, wetting time, wetting ratio and T85% of AT tablets Formulation Disintegration Wetting time Water T85% (min.) Code Time (Sec.) (Sec.) absorption ratio AT1 39 ± 3.05 31 ± 2.75 42.25 ± 3.85 5 ± 0.5 AT2 28 ± 1.52 20 ± 1.57 58.75 ± 4.57 2 ± 1.0 AT3 38 ± 3.0 29 ± 2.15 54.60 ± 5.85 4 ± 1.5 AT4 154 ± 3.21 125 ± 4.50 35.95 ± 4.80 45 ± 2.5 AT5 93 ± 2.51 78 ± 3.75 41.15 ± 6.75 25 ± 4.0 AT6 122 ± 1.52 96 ± 3.50 38.20 ± 4.65 40 ± 3.5 AT7 497 ± 3.05 418 ± 6.35 12.40 ± 4.50 65 ± 4.5 AT8 426 ± 3.5 355 ± 5.87 23.37 ± 5.45 40 ± 3.0 AT9 476 ± 2.75 378 ± 5.42 19.25 ± 6.34 50 ± 4.0 Dissolution study of atenolol core tablets as showed in figure 33. In vitro dissolution study indicated that as the amount of sodium starch glycolate increased upto optimum level (5 mg), the rate of drug release increased due to faster disintegration of tablets. But, as the amount of sodium starch glycolate increased beyond the 5 mg, the rate of drug release was decreased, because sodium starch glycolate might have formed a thick barrier to the further penetration of the disintegration medium and hindered the disintegration or leakage of tablet contents (Kalpesh et al., 2011). The AT2 formulation containing 5 mg of sodium starch glycolate showed higher rate of drug release and least 2 ± 1.0 min T85%. So, AT2 formulation showed optimum performance. Rajesh A. Keraliya 122

% Cumulative Drug Release Ph.D Thesis 120 Drug release study of Atenolol core tablets 100 80 60 40 20 0 0 10 20 30 40 50 60 70 Time (min.) A1 A2 A3 A4 A5 A6 A7 A8 A9 Figure 33: Dissolution profile of atenolol core tablets 5.5.5. Statistical analysis for optimization of formulation of atenolol core tablets Linear model used to check effect of individual two factors on response in polynomial equation, while, quadratic model used to check effect of individual two factors on response in polynomial equation plus to check effect of square of individual two factors on response in polynomial equation. But by default, DOE suggested linear model according to data. A 3 2 factorial design was adopted; the response values subjected for this analysis were T85%. Table 19 showed that values of response T85% for the AT1 to AT9 formulations containing different amount of SSG and PVP K30. It was logically decided to obtain minimum T85% from the formulated products. The results for T85%, a dependent variables of the batches are shown in table 19 and equation 8 and 9 represent the polynomial equations in terms of coded factors and actual factors respectively. Polynomial equation in terms of coded factors T85% = +30.11 2.64 *A + 24.05 * B. (8) Polynomial equation in terms of coded factors T85% = -12.71 1.05 *SSG + 4.81 * PVP. (9) Rajesh A. Keraliya 123

Table 19: Results of T85% for atenolol core tablets Formulation code Independent variables coded value Independent variables actual value Dependent variable Amount of Amount of Amount of Amount of SSG (mg) PVP (mg) SSG (mg) PVP (mg) (A) (B) (A) (B) T85% (Y) (min.) AT1-1 -1 2.50 5.00 5 AT2 0-1 5.00 5.00 2 AT3 +1-1 7.50 5.00 4 AT4-1 0 2.50 10.00 45 AT5 0 0 5.00 10.00 25 AT6 +1 0 7.50 10.00 40 AT7-1 +1 2.50 15.00 65 AT8 0 +1 5.00 15.00 40 AT9 +1 +1 7.50 15.00 50 A coefficient with a positive sign shows a synergistic effect whereas a coefficient with a negative sign shows an antagonistic effect. In equation 8, A coefficient of Independent factor A with a negative sign ( 2.64 *A) indicates on increased the amount of SSG, T85% decreased (as shown in table 19, formulation AT1 & AT2, AT4 & AT5, and AT7 & AT8). T85% decreased from 5 min to 2 min as the SSG level in AT2 formulation is increased to 5 mg from 2.5 mg of AT1 formulation. Whereas, a coefficient of Independent factor B with a positive sign (+ 24.05 * B) indicated T85% increased as the amount of PVP K30 increased (In table 19, Formulation AT1 to AT9). T85% increased from 2 min to 25 min as the PVP K30 level in AT5 formulation is increased to 10 mg from 5 mg of AT2 formulation. Analysis of variance (ANOVA) study for response surface linear model showed the p-value of model is 0.0033 which is less than 0.0500 indicated model terms are significant and value of correlation coefficient is (R 2 ) 0.9752 which indicated that a goodness of fit of model. The polynomial Equation can be used to draw conclusions after considering the magnitude of coefficient and the mathematical sign it carries, (i.e. positive or negative). Rajesh A. Keraliya 124

Figures 34 and 35 describe the effect of independent variables on response T85%. One factor plot showed in figure 34 indicated that as the amount of SSG increased from low to medium level, T85% decreased as the formulation disintegrated quickly, on increased the amount of SSG due to swelling of SSG lead to rapid disintegration of core tablets, but, as the amount of SSG increased from medium to high level, T85% increased due to formation of a viscous gel layer by sodium starch glycolate which prevent the penetration of the disintegration medium (Bolhuis et al., 1997). While, as the amount of PVP K30 increased, T85% also increased because of PVP K30 bind the particles together and form harder tablet. So, when amount of PVP K30 increased, disintegration time of tablets also increased (figure 35). Result suggested that the presence of SSG and PVP K30 were essential for achieving desired T85%. Design-Expert Software Factor Coding: Actual T85 (min) Design Points 95% CI Bands X1 = A: SSG Actual Factor B: PVP = 10 70 60 50 One Factor T 8 5 (m in ) 40 30 20 10 0 2.5 3.5 4.5 5.5 6.5 7.5 A: SSG (mg) Figure 34: Effect of amount of SSG on T85% The relationship between the dependent and independent variables was further elucidated using contour plots (figure 36) and 3-D response plot (figure 37). Logically, it was predecided to obtain the minimum T85% (T85% = 5 min.) for the formulated products. The results for dependent variables T85% of the batches are shown in table 19. In contour plot and 3-D response plot showed that only formulation AT2 had T85% near to desired T85% (figure 36 & 37, indicated by light blue). Rajesh A. Keraliya 125

Design-Expert Software Factor Coding: Actual T85 (min) Design Points 95% CI Bands X1 = B: PVP Actual Factor A: SSG = 5 80 60 One Factor T 8 5 (m in ) 40 20 0-20 5 7 9 11 13 15 B: PVP (mg) Figure 35: Effect of amount of PVP K30 on T85% Design-Expert Software Factor Coding: Actual T85 (min) Design Points 64.6 7.5 T85 (min) 1.8 6.5 X1 = B: PVP X2 = A: SSG A : S S G (m g ) 5.5 4.5 10 20 30 40 50 3.5 2.5 5 7 9 11 13 15 B: PVP (mg) Figure 36: Contour plot showing the effect of SSG and PVP K30 on T85% Optimization of result For the optimization of atneolol core tablet formulation, constraints were fixed for all factors and response. Constraints were set according to formulation of atenolol core tablet using minimum amount of excipients, which would give desired response. In the present Rajesh A. Keraliya 126

study, T85% was predecided 2 min. In overlay plot for optimization, data presented in white box was obtained when desirability value 1.0 was got and desirability value 1.0 or near to 1.0 indicated optimum formulation. Overlay plot indicated that 4.56 mg of SSG and 5.76 mg of PVP K30 containing atenolol core tablet achieved desired near to 2 min T85% (figure 38). Validation of optimization technique was done by preparing checkpoint batch and responses were evaluated. The response value observed in the checkpoint batch was closet to theoretical value obtained from polynomial equation. Design-Expert Software Factor Coding: Actual T85 (min) Design points above predicted value Design points below predicted value 64.6 1.8 X1 = B: PVP X2 = A: SSG 80 60 40 T 8 5 (m in ) 20 0-20 7.5 6.5 5.5 A: SSG (mg) 4.5 3.5 2.5 5 7 9 11 13 15 B: PVP (mg) Figure 37: 3-D response plot showing the effect of SSG and PVP K30 on T85% Design-Expert Software Factor Coding: Actual Overlay Plot 10.00 Overlay Plot T85 Design Points X1 = A: Amount of SSG X2 = B: Amount of PVP B : A m o u n t o f P V P (m g ) 9.00 8.00 7.00 6.00 T85: 2.00045 X1 4.56 X2 5.76 T85: 2 5.00 2.50 3.50 4.50 5.50 6.50 7.50 A: Amount of SSG (mg) Figure 38: Overlay plot for optimization of atenolol core tablet formulation Rajesh A. Keraliya 127

5.5.6. Stability study The optimized AT2 batch of atenolol core tablets were subjected for accelerated stability studies according to ICH guidelines (40 ± 2 0 C and 75 ± 5% RH) for a period of 6 months in a stability chamber. Formulations did not show any significant changes in the drug content, hardness, disintegration time and in vitro dissolution during stability study as shown in table 20. Hence, the AT2 atenolol core tablets were sufficiently stable as per regulatory requirements. Table 20: Stability study of optimized atenolol core tablets Tests Initial 1 month 2 months 3 months 6 months Drug content (%) 99.97 ± 1.3 99.98 ± 1.8 99.95 ± 1.4 99.92 ± 1.5 99.88 ± 1.52 (Avg. ± SD) Hardness 3.25 ± 0.15 3.25 ± 0.1 3.25 ± 0.5 3.25 ± 0.25 3.5 ± 0.25 (kg/cm 2 ) Disintegration 28 ± 1.52 29 ± 1.40 31 ± 1.38 32 ± 1.25 33 ± 1.40 time (sec.) T85% (min.) 2 ± 1.0 2 ± 1.08 2 ± 1.25 2 ± 1.32 2 ± 1.45 CONCLUSION The fast disintegrating core tablet of atenolol were prepared using different amount of superdisintegrant (SSG) and dry binder (PVP K30). Atenolol core AT2 tablet containing 5 mg of SSG and 5 mg of PVP K30 showed good hardness and faster disintegration. Fast disintegration of core tablet requires in press coated pulsatile release tablets to achieve burst release after lag time. So, optimized atenolol core AT2 tablet, used for preparation of press coated pulsatile formulation of atenolol in further studies. Rajesh A. Keraliya 128