ISOLATION, CHARACTERIZATION AND INVESTIGATION OF STARCH PHTHALATE AS NOVEL SUPERDISINTEGRANT IN DEVELOPING OF ACYCLOVIR FAST DISSOLVING TABLETS

Acyclovir, an anti-viral drug widely used in the treatment of herpes simplex virus infections, characterized by low aqueous solubility. The present study focuses on the formulation and evaluation of Acyclovir fast dissolving tablets which offer a solution for those patients having difficulty in swallowing. In the formulation of fast dissolving tablets of acyclovir, superdisintegrants like starch phthalate (a novel superdisintegrant), croscarmellose sodium and crospovidone are employed. The synthesized starch phthalate was characterized by FTIR, X-ray etc. The Acyclovir Starch phthalate compatibility studies like DSC, FTIR and TLC were done. From the results, it was observed that no chemical interaction between the drug and starch phthalate confirmed. 2 factorial design was used in formulation of tablets to obtain the ideal concentration of starch phthalate that is to be used in the formulation of fast dissolving tablets with less experimentation and in short period of time. Acyclovir fast dissolving tablets were subjected to various physical tests and in-vitro dissolution studies. The studies revealed that concentration of 10% w/w of starch phthalate can be used as superdisintegrant in the formulation of fast dissolving of fast dissolving tablets.


Need for formulation of Fast Dissolving Drug Delivery Systems:
The need for non-invasive delivery systems persists due to patient's poor acceptance and compliance with existing delivery regimens, limited market size for drug companies and drug uses, coupled with high cost of disease management.

Preparation of Starch Phthalate (A Novel Superdisintegrant):
Initially Phthalic anhydride was dissolved in 2ml of dimethyl sulphoxide (DMSO) and the pH was adjusted to 3.5 using 10M NaOH and finally made upto 50ml.To this potato starch was added and conditioned for 16 hrs; the product was kept in oven at 60 0 C for 1hr.Then the product was mixed with acetone for 15min and then washed with Isopropanol to remove any unwanted Phthalic anhydride if present.After washing, the resultant starch phthalate was kept in oven at 60 0 C until it gets dried.The product obtained was ground and sized.

Characterization of starch phthalate:
The Starch Phthalate prepared was evaluated for the following: Solubility: Solubility of Starch phthalate was tested in water, aqueous buffers of pH 1.2, 4.5 and 7.4 and organic solvents such as alcohol, dichloromethane, chloroform, and acetone and petroleum ether.

pH:
The pH of 1% w/v slurry was measured and recorded.
Melting Point: Melting point was determined by using melting point apparatus.
Viscosity: Viscosity of 1% dispersion in water was measured using Ostwald Viscometer.
Swelling Index: Starch phthalate (200 mg) was added to 10ml of water and light liquid paraffin taken in two different graduated test tubes and mixed.The dispersion in the tubes was allowed to stand for 12h.The volumes of the sediment in the tubes were recorded and calculated as per the standard formula for swelling index.
Test for Gelling Property: The gelling property (gelatinization) of the starch and starch phthalate prepared was evaluated by heating a 7% w/v dispersion of each in water at 100 o C for 30 min.

Moisture Absorption:
The hygroscopic nature of starch phthalate was evaluated by moisture absorption studies in a closed dessicator at 84% relative humidity and room temperature.
Particle Sizes: Particle size analysis was done by sieving using standard sieves.
Density: Density (g/cc) was determined by liquid displacement method using benzene as liquid.
Bulk Density: Bulk density (g/cc) was determined by three tap method in a graduated cylinder.
Angle of Repose: Angle of repose was measured by fixed funnel method.
Compressibility Index: Compressibility index (CI) was determined by measuring the initial volume (V o ) and final volume (V) after hundred tapings of a sample of starch phthalate in a measuring cylinder.CI was calculated as per standard formula.
FTIR Spectroscopy: FTIR spectra of starch phthalate were recorded on samples prepared in potassium bromide (KBr) disks using a BRUKER FT-IR, (Tokyo, Japan).Samples were prepared in (KBr) disks by means of a hydrostatic press at 6-8 tons pressure.The scanning range was 500 to 4000 cm -1 .
X-ray diffraction: Diffraction pattern of starch phthalate was recorded with an X-ray diffractometer (Analytical spectris Pvtd., Singapore

Optimization Technique:
Optimization technique provide both a depth of understanding and an ability to explore and define ranges for formulation and processing factors with a rational approach to the selection of several experimental and manufacturing step for a given product, to quantitatively select a formulation.It is at this point that optimization can become a useful tool to quantitative a formulation that has been qualitatively determined.
The present investigation deals with an attempt of systemic formulation approach for optimization of acyclovir fast dissolving tablets employing starch phthalate, croscaramellose sodium and crospovidone as superdisintegrants.A 2 3 factorial design was applied to investigate the main and interaction effects of the three formulation variables i.e., starch phthalate (A), croscaramellose sodium (B) and crospovidone (C) in each case to find the formula with less disintegration time and more dissolution efficiency 1min and to permit arbitrary selection of tablets with immediate release of drug with in 5 min.

Formulation of Acyclovir Fast Dissolving Tablets as per 2 3 Factorial Designs:
The tablets were prepared by direct compression method.The composition of different formulations of Acyclovir fast dissolving tablets is shown in Table 1.
For uniformity in particle size each ingredient was passed through # 100 mesh sized screen before mixing.Starch phthalate, Crosspovidone, Microcrystalline cellulose, Croscarmellose Sodium, Starch were accurately weighed and mixed using mortar and pestle, and then added to Acyclovir.Finally Talc and Magnesium Stearate were added to the powder.Finally mixed blend was compressed by using eight station rotator presses (Shakthi Machineries Pvt. Ltd., Ahmedabad, India).

Evaluation of Acyclovir Fast Dissolving Tablets:
Hardness: The hardness of prepared formulation was measured by using Monsanto hardness tester.
Friability: The friability of tablets was measured using a Roche friabilator.
Drug Content Uniformity: For content uniformity test, twenty tablets were weighed and powdered a quantity of powder equivalent to 10mg of acyclovir was extracted into 0.1 N HCL and filtered.The acyclovir content was determined by measuring the absorbance spectrophotometrically at 254 nm after appropriate dilution with 0.1 N HCL.The drug content was calculated using the standard calibration curve.The mean percent drug content was calculated as an average of three determinations.

Wetting Time:
The wetting time of the acyclovir fast dissolving tablets was measured using a very simple process.Five circular tissue papers of 10 cm diameter were placed in a Petri dish with a 10 cm diameter.Ten milliliters of water containing a water soluble dye (Amaranth) was added to the Petri dish.A tablet was carefully placed on the surface of tissue paper.The time required for water to reach the upper surface of the tablet was noted as the wetting time.
Water absorption ratio: A piece of tissue paper folded twice was placed in a small Petri dish containing 6ml of water.A tablet was put on the tissue paper and allowed to completely wet.The wetted tablet was then weighed.Water absorption ratio (R) was determined using following equation.In-vitro Disintegration Time: Disintegration time for FDTs was determined using USP disintegration apparatus with 0.1 N HCL.The volume of medium was 900 ml and temperature was 37 ± 0.2 o C. The time in seconds taken for complete disintegration of the tablet with no palatable mass remaining in the apparatus was measured.

In-vitro Dissolution Rate Studies:
The In-Vitro dissolution rate study of acyclovir fast dissolving tablets was performed using 8-station dissolution test apparatus (Electrolab TDT-08L) fitted with paddles (50 rpm) at 37 ± 0.5 o C, using 0.1N HCL (900 ml) as a dissolution

RESULTS AND DISCUSSION:
The starch phthalate prepared was found to be fine, smooth and free flowing amorphous powder.The physical and micromeritic properties of the starch phthalate are summarized in Table 2.It was insoluble in aqueous solvents and insoluble in organic solvents tested (methanol, petroleum ether, dichloromethane and chloroform) the pH of 0.1 % aqueous dispersion was 2.88.Starch phthalate exhibited good swelling in water.The swelling index was 68%.All micromeritic properties indicated good flow and compressibility need for solid dosage from manufacturing.The density of starch phthalate was found to be 0.555 g/cc.
The FTIR spectrum of starch and starch phthalate is shown in Figure 1.The presence of peaks of absorption at 1691.57cm -1 characteristic peaks of esters.So from FTIR studies it was concluded that starch phthalate (ester) was formed when starch was allowed to react with Phthalic anhydride.The disappearance of pink color in the ester test confirmed the presence of ester, i.e, and starch phthalate.The characteristic FTIR bands of Acyclovir at 2926.01cm -1 (C-H), 3441.01 cm -1 (N-H) were all observed in the FTIR spectra of both AC and AC-SP.These FTIR spectral observations also indicated no interaction between starch phthalate and drug selected.3) indicated no interaction between the drug and starch phthalate.4.0 ± 0.04 0.12 ± 0.013 14.17 ± 0.11 09 ± 03 10 ± 0.17 42.5 ± 0.01 The results of In-Vitro wetting time and water absorption ratio were found to be within the prescribed limits and satisfy the criteria of the fast dissolving tablets (Figure 4).The In-Vitro wetting time was less in F 8 which consists of combination of 10% starch phthalate, 5% croscaramellose sodium and 5% crospovidone.The dissolution parameters of the formulation from (F 1 -F 8 ) which were made by direct compression method were shown in the Table 5.In all these cases the PD 1 (percent dissolved in 1minute) was more in F 8 which consists of 10% starch phthalate, 5% croscaramellose sodium and 5% crospovidone.The same was in the ISSN: 2250-1177 [39] CODEN (USA): JDDTAO case of DE 1 % (dissolution efficiency in 1min).The PD 1 &DE 1 % reveals that starch phthalate was effective at 10% starch Phthalate, 5% croscaramellose sodium and 5% crospovidone when the formulations were made by direct compression using these superdisintegrants.
The K 1 also increased in all the formulations when compared to F1 formulation.The number of folds increase in DE 1 % and number of folds increase in K 1 (min-1 ) were given in the Table 5.From the results it was concluded that starch phthalate (new superdisintegrant) could be used as a superdisintegrant in the formulation of fast dissolving tablets of acyclovir.

Table 5: Dissolution Parameters of Acyclovir Fast Dissolving Tablets Employing Starch Phthalate and Other Superdisintegrants
Experimental design: Optimization of the acyclovir fast dissolving tablets was done using 2 3 factorial designs in which 3 factors each at two levels were evaluated.To evaluate the individual and combined effects of starch phthalate (factor A), croscaramellose sodium (factor B) and crospovidone (C).The disintegration time and dissolution efficiency in 1min, the fast dissolving tablets were formulated using selected combinations of three factors as per 2 3 factorial designs.Formula of acyclovir fast dissolving tablets was prepared as per 2 3 factorial designs given in the Table 6.A polynomial regression algorithm was used to rotate the independent variables to the response variables.The general first order model and equation they could be constructed from 2 n experimental design is indicated in the following equation.
Where y is the measured response, β 0 is the arithmetic mean response of 1min, β 1 , β 2 , β 3 , β 1 β 2 , β1 β 3 , β 2 β 3 , β 1 β 2 β 3 are coefficients for the corresponding factors and A, B, C, AB, AC, BC, and ABC are the percentages of starch phthalate, croscaramellose sodium and crospovidone and interaction terms respectively.The coefficients were calculated accordingly to the general formula given in equation.

B = ΣXY/2 n
Where β is coefficient, X is the corresponding variable (A, B, C) and Y is the response value (disintegration time and dissolution efficiency in 1minute), n is the level.
The two levels of three factors employed in the experimental design are indicated in Table 6 and transformed design for analysis of responses of acyclovir fast dissolving tablets is shown in Table 7.The value of the R 2 indicates the good fit.The polynomial equations can be used to draw a conclusion after considering the magnitude of coefficient and the mathematical sign it carries (Positive or Negative).
From the polynomial equations one can easily deduce that the factor B, C and interaction BC and ABC have negative effect on the disintegration time of acyclovir fast dissolving tablets.Factor A and interactions of AB and AC have positive effect on the disintegration time.
Except the factor A and interaction of AB all the other main and interaction terms have positive effect on the dissolution efficiency in 1min.
Once the polynomial equations were developed which relate the levels of each other and their corresponding interactions with disintegration time and dissolution efficiency in 1 min, the surface response curves and counter plots were constructed using software.
The response surface plots and contour plots reveal that as the concentration of starch phthalate (A), croscaramellose sodium (B) and crospovidone (C) increases, disintegration time decreases.The effects of A and B on disintegration time are shown in Figure 6.No visible changes were observed in the fast-dissolving tablets after storage.Drug dissolved from the fastdissolving tablets were evaluated before and after storage in each case.No significant difference (P >0.05) was observed in the percent drug content before and after storage for 6 months.The drug release profiles of the fast-dissolving tablets before and after storage are given in Table 8.The drug release characteristics of the formulation tested remained unaltered during the storage period.The results, thus, indicated that the drug content and drug release rate of the fast dissolving tablets formulated employing starch phthalate were quite stable.From the above data, the ideal concentrations of the superdisintegrant that are to be used in fast dissolving tablets to have less disintegration time and more dissolution efficiency in 1min is factor (A) i.e starch phthalate (5-6%), factor (B) croscaramellose sodium (4-5%) and factor (C) i.e crospovidone ( 4-5%) were found to be ideal.

CONCLUSION:
Fast dissolving drug delivery is a topic of current interest in pharmaceutical technology.In the present investigation Starch phthalate, a new polymer was prepared and evaluated for its application as superdisintegrant in fast dissolving dosage form.Starch phthalate was found to be a better superdisintegrant with the Acyclovir and Ibuprofen and hence it could be used in the formulation of fast dissolving tablets to provide fast dissolving release of the contained drug for 5 minutes.Drug release characteristics of the fast dissolving tablets formulated employing starch phthalate were quite stable and remained unaltered when subjected to accelerated stability testing at 40 0 ± 2 0 C and 75% RH for 6 months.

FTIR
Spectroscopy: FTIR spectra of Acyclovir and their mixtures (1:1) with starch phthalate were recorded on a Perkin Elmer, IR Spectrophotometer model: Spectrum RXI, using KBr disc as reference.TLC Study: TLC was carried out on Acyclovir and their mixtures (1:1) with Starch Phthalate follows: Stationary Phase: Silica gel G (per coated TLC plates) Mobile Phase: Dichloromethane: Methanol: Ammonia solution (80:20:2)Procedure: Mobile phase was prepared and taken in a TLC chamber.The chamber was allowed to saturate with solvent vapor for 24h.Standard (pure drug) ant test (drug-starch phthalate mixtures) sample were spotted on activated silica plates using narrow capillary tubes.The spotted plates were kept in the TLC chamber and allowed to run the mobile phase.The plates were dried and kept in iodine chamber to develop the spots.The R f values of standard and test samples were determined by the following formula.Distance travelled by sample/ distance travelled by solvent front.
R = 100 (W a -W b )/W a Where, W a = Weight of tablet after water absorption, W b = Weight of tablet before water absorption.

Figure 2 : 3 .
Figure 2: DSC of Drug and Starch Phthalate In the TLC study, single spots were observed in the case of pure drug as well as their mixtures with starch phthalate shown in Figure 3.The close agreement of the

Figure 3 :
Figure 3: TLC of Drug and Starch Phthalate

Figure 4 :
Figure 4: Wetting Time of Acyclovir Fast Dissolving Tablets The drug dissolution from the Acyclovir fast dissolving tablets employing starch phthalate and other known superdisintegrants were shown in the Figure 5.

Figure 5 :
Figure 5: Dissolution Profiles of F 1 to F 8 Formulations

Figure 6 :
Figure 6: (A) Response Plot (B) Contour Plot of Acyclovir Fast Dissolving Tablets (Effect of Starch Phthalate and Croscaramellose Sodium on Disintegration Time)

Figure 7 :Figure 8 :
Figure 7: (A) Response Plot (B) Contour Plot of Acyclovir Fast Dissolving Tablets (Effect of Croscaramellose Sodium and Crospovidone on Disintegration Time)

Figure 9 :Figure 10 :Figure 11 :
Figure 9: (A) Response Plot (B) Contour Plot of Acyclovir Fast Dissolving Tablets (Effect of Starch Phthalate and Croscaramellose Sodium on Dissolution Efficiency in 1min)

Table 1 : Formula of Acyclovir Fast Dissolving Tablets Employing Starch Phthalate Ingredients (Mg/tablet)
At the predetermined time intervals, 5 ml samples were withdrawn, filtered through 0.45 µ membrane filter, diluted and assayed at 254 nm using a UV/Visible Double beam spectrophotometer (Analytical technology T360).Cumulative percentage drug release was calculated using standard absorbance from the calibration curve.All the dissolution experiments were conducted in triplicate (n=3).

Table 3 : R f Values of Selected Drugs And Their Mixtures (1:1) With Starch Phthalate
Weight loss on the friability test was less than 0.15 % in all cases.All the fast dissolving tablets prepared contained Acyclovir with in 100 ± 5% of the labeled claim.As such the prepared tablets were of good quality with regard to drug content, hardness and friability.The disintegration time of all the formulated tablets was found to be in the range of 9 ± 0.6 to 48 ± 0.5 seconds as indicated in the Table4.
Thus the results of FTIR and TLC indicated no interaction between the selected drug and starch phthalate, the new superdisintegrant.Hence, starch phthalate could be used as a superdisintegrant in the design of fast dissolving tablets of the selected drugs.Fast dissolving tablets each containing 200mg of Acyclovir could be prepared by employing starch phthalate and other known superdisintegrants, crospovidone and croscaramellose sodium by direct compression method.Hardness of the tablet was in the range of 3-6 kg/sq.cm.It indicates good strength with a capability to resist physical and pre-functionary stress ISSN: 2250-1177 [38] CODEN (USA): JDDTAO conditions during handling.