The Best Superdisintegrant Having Excellent Disintegrating Ability Biology Essay

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The Crosspovidone is water insoluble tablet disintegrant used at 2-5 concentration in tablet prepared either by direct compression or wet and dry granulation technique. It quickly exhibit high capillary action and pronounced hydration capability with little affinity of crosspovidone strongly influence disintegration of tablets. Larger particles offer a faster rate of disintegration than smaller particles. Crosspovidone also be used as a solubility enhancer with the method of co evaporation. It was also used to improve the solubility of poorly water soluble drugs. The drug is adsorbed on to crosspovidone in the presence of a appropriate solvent and the solvent is then evaporate. This method results in faster rate of dissolution.

Formulation C1, C2, C3 and C4 containing Starlac® as a filler binder which is a co processed excipients consist of lactose and maize starch (85:15) produced by spray drying. As lactose is water soluble in nature and starch contains disintegrant property, upon contact with dissolution medium formulations containing Ac-Di-Sol® with Starlac® get easily erodes, rather than swelling of Ac-Di-Sol® in core tablet.

As the concentration of Ac-Di-Sol increases show decrease in the disintegration time and increase in dissolution of drug. From drug release it was observed that increase in concentration of Ac-Di-Sol increases the drug release upto 2% concentration in the tablet, but further increase in the concentration of Ac- Di-Sol not show any increase in the dissolution rate.

As the concentration of Ac-Di-Sol was increases show decrease in the disintegration time and increase in dissolution of drug. 100% drug were released from the all the formulation A1, A2, A3 and A4 in 24, 18, 20, 16 minutes respectively. From drug release it was observed that increase in concentration of Ac- Di-Sol increases the drug release.

EFFECT OF TYPE OF POLYMER AND IT'S VISCOSITY ON DRUG RELEASE FROM THE PRESS COATED TABLET

The formulation F1, F2 and F3 was having HPC EXF erodible, HPC HF gellable and HPC LF rupturable nature respectively. The formulation F1 shows lag time upto 5 hours, formulation F2 having lag time more than 24 hours and formulation F3 having lag time upto 6 hours, because our press coated tablets contained no drugs in the shell and the release of drug is presumed to commence when the outer shell is removed by dissolution or erosion of the hydrophile gelation layers formed on the core surfaces. Therefore, the lag time should be longer with increasing HPC viscosity because the dissolution rate or erosion rate of the polymer would be delayed as the molecular weight increased similarly to the matrix type tablets.105, 108

The formulation F4 having outer layer of rupturable material ethyl cellulose (EC N22), which showed the lag time upto 5 hours. The main use of ethylcellulose in oral formulations is as a hydrophobic coating agent for tablets and granules Ethylcellulose coatings are used to modify the release of a drug to mask an unpleasant taste, or to improve the stability of a formulation; for example, where granules are coated with ethylcellulose to inhibit oxidation. Modified-release tablet formulations may also be produced using ethylcellulose as a matrix former Ethylcellulose, dissolved in an organic solvent or solvent mixture, can be used on its own to produce water-insoluble films. Higher-viscosity ethylcellulose grades tend to produce stronger and more durable films. Ethylcellulose films may be modified to alter their solubility, by the addition of hypromellose or a plasticizer; An aqueous polymer dispersion (or latex) of ethylcellulose such as Aquacoat ECD (FMC Biopolymer) or Surelease (Colorcon) may also be used to produce ethylcellulose films without the need for organic solvents.

The formulation F5 having outer layer of Spray-dried lactose (Pharmatose® DCL 11) which showed the lag phase upto 1 hour. Actually spray-dried lactose (Pharmatose® DCL 11) is formed by spray drying the slurry contain lactose crystals. The final product contains combination of crystals of lactose monohydrates and sphere-shaped agglomerates of small crystals seized in concert by glass or amorphous material. The previous contribute fluidity and the final gives the compressibility to the product. It has excellent flow properties as well as binding properties. It deform plastically compare to the similar sized α-Lactose monohydrate particles. Amorphous portion of the spray dried lactose is accountable for the improved binding and plastic deformation. Compressibility is exaggerated if it is allowed to dry under a level of 3% w/w moisture. Disintegration is necessary in the formulations contain spray-dried lactose.

The formulation F6 having outer layer of xanthan gum, which showed the lag time more than 24 hours, the initial increase in drug release rate on increasing the concentration of xanthan gum can be explained on the basis that a higher concentration led to an increase in hardness of the tablet, while the porosity and capillary pore sizes were reduced.110 Xanthan gum is a polysaccharide consisting of a cellulose backbone and Trisaccharide side chains containing glucuronic acids that give this polymer a negative charge. Although primarily used as a suspending agent, xanthan gum has been reported to function as a matrix retardant in solid dosage forms.111, 112, 113, 114, 115 This in turn reduced the wicking of water into the tablet and consequently the swelling and drug release rates are slowed. These tablets showed a considerable swelling at a pH of 6.8 and the drug was dispersed in the swollen matrix formed by the polysaccharide.

The formulation F7 having outer layer of locust bean gum, which showed the lag time upto 3 hours, Locust bean galactomannan were found to be soluble in water. Cross-linked galactomannan though lead to water insoluble film forming product show degradation in colonic microflora.116 However, dissolution study performed on theophylline tablets coated with cross-linked galactomannan showed the mechanical unsteadiness of these coatings in the dissolution media,117 thus signifying the nonsuitability of such films as colon carriers.

The formulation F8 having outer layer of Di-TAB which showed lag time of only 1 hour. This anhydrous dibasic calcium phosphate di hydrate is used together as an excipient and as a supply of calcium in nutritional supplements. It is used mainly in the nutritional or health food sector. It is also used in pharmaceutical products since of its compaction property, and fine flow properties of the coarse rating material. Dibasic calcium phosphate di hydrate is non hygroscopic and stable at room temperature. However, under certain conditions of temperature and humidity, it can lose water of crystallization below 1000C. This has implication for certain types of packaging and aqueous film coating since the loss of water of crystallization appear to be initiated by high humidity and by implication high moisture vapor concentrations in the vicinity of the dibasic calcium phosphate dehydrate particles. It is also used in toothpaste and dentifrices formulations for its abrasive properties.

EFFECT OF OUTER LAYER THICKNESS OF POLYMER IN THE OUTER SHELL

Increasing the amount of outer shell seemed to prolong lag time since the time required to complete the dissolution or erosion of the outer shell would be longer. Therefore, press coated tablets were prepared with different amounts of HPC-HF in the outer layer with inner core tablets.

EFFECT OF ERODIBLE MATERIAL (KLUCEL EXF) COMBINED WITH RUPTURABLE MATERIAL (EC) IN THE OUTER SHELL

By combining erodible polymer (HPC-EXF) with rupturable polymer (EC) lag time increases with increasing weight ration of HPC-EXF/EC in formulation F11 to F17. But while using EC alone, lag time is lowest as compared to any weight ratio of HPC-EXF/EC. This is only because while combining hydrophilic HPC-EXF with EC; HPC-EXF acts as a binder too. As tablet comes in the contact of dissolution medium HPC-EXF starts hydrating but as EC is hydrophobic in nature it retards the hydration of HPC-EXF and as EC is semi permeable in nature105 dissolution medium penetrates faster in EC coated tablet compared to along with HPC- EXF. As HPC-EXF forms a compact with EC water would not penetrate faster as compared to EC outer coating shell. Thus due to both concomitance effect lag time is increased with increasing weight ratio of EC/HPC-EXF.

As HPC-EXF made a compact with EC; because of different weight ratio of EC/HPC-EXF, outer shell may get eroded first and then when sufficient internal pressure built because of AC-Di-Sol® present in formulation F11 to F17 outer shell broke into two halves and cause a stage of rapid drug release. Obviously, the period of lag time was different and dependent on the weight ratio of HPC-EXF/EC. In that also formulation F11 having EC N7 grade and F12 having EC N10 grade which are more rupturable than grade EC N22 which is used in formulation F13 to F17. The order of the time lag changed according to the weight ratio of HPC-EXF/EC mixture as follows: F11 (50:50) 5 hours, F12 (50:50) 6 hours, F13 (50:50) 6 hours, F14 (87.5:12.5) 7 hours, F15 (75:25) 6 hours, F16 (25:75) 8 hours and F17 (12.5:87.5) 9 hours. The finding indicates that the time lag of a press coated tablet can be modulated from 5 to 9 hours by combining EC with HPC-EXF in different weight ratio.

EFFECT OF ERODIBLE MATERIAL (HPC-EXF) COMBINED WITH GELLABLE MATERIAL (HPC-HF) IN THE OUTER SHELL

Formulation F18 to shows increase in lag time and decrease in Montelukast Sodium release rate with increase in weight ration of HPC EXF: HPC HF. Formulation F18 contains HPC EXF: HPC HF weight ratio of 87.5:12.5. When HPC-HF combines with HPC-EXF in this ratio, the final viscosity of this mixture increase that of HPC-EXF alone. Upon contact with dissolution medium it forms a gel like structure. But due to higher weight % of HPC-EXF, this formed gel is not so firm but it is eroded and gelled simultaneously. Formulation F18 shows the drug release by bursting effect as pressure generate in core tablet is enough to separate two halves or break the coating layer after some erosion of the outer shell and shows the lag time of 7 hours. When core tablet present in formulation F18 hydrates by dissolution medium, due to Ac-Di-Sol® present in it, in presence of avicel® it swells and give rapid drug release. The initial slow drug release was because of dissolution medium penetrating into the shell and as it hydrates the core due to tight gelled structure of shell some drug is eject out by diffusion mechanism and when internal pressure is enough to break the coating layer rapid drug release was observed.

Formulation F19 contains HPC EXF: HPC HF weight ratio of 75:25. Here almost same release pattern was observed as in formulation F18. The difference is increase in lag time as increase in weight ratio of HPC EXF: HPC HF. Internal pressure generate in core tablet of formulation F19 is also enough to break the coat. Formulation F19 shows the lag time of 9 hours and showing release at 10 hours.

Formulation F20 contains HPC EXF: HPC HF weight ratio of 50:50. When HPC-HF combined with HPC-EXF in the weight ratio of 50:50 it forms a more tight gelled structure of outer coating layer. Formulation F20 shows no drug release upto 10 hours. Formulation F20 shows only 56% drug released in 24 hours. Because of core tablet contains avicel with Ac-Di-Sol® in the formulation F20, as avicel® is hydrophobic in nature; the penetrant dissolution medium is insufficient to hydrate the core so as to diffuse out Montelukast Sodium from the outer gelled shell. And it requires more time to hydrates the avicel® present in formulation F20. As Starlac® contains 85% lactose and 15% maize Starch; it gives the drug release fast as compared to formulation F20 by diffusion mechanism due to combined effect of rapid hydration and disintegrant property. Pressure generate after complete hydration of core tablet in formulation F20 was not enough to break the outer shell.

Formulation F21 contains HPC EXF: HPC HF weight ratio of 25:75. Here also almost same release pattern was observed as that of formulation F20, only difference was in the delay in lag time and delay in release rate of Montelukast Sodium from the gellable barrier formed by high weight ratio of HPC EXF: HPC HF. Formulation F21 shows lag time of 20 hours. Only 16% drug release observed with formulation F21. Formulation F22 contains HPC EXF: HPC HF weight ratio of 12.5:87.5. Formulation F22 shows no drug release within 24 hours period of time.

Therefore, the lag time should be longer with increasing HPC viscosity because the dissolution rate or erosion rate of the polymer would be delayed as the molecular weight increase similarly to the matrix type tablets62 and also depends upon the design of core tablets.

EFFECT OF ERODIBLE MATERIAL (KLUCEL EXF) COMBINED WITH INERT HYDROPHILIC EXCIPIENTS (PHARMATOSE® DCL 11) IN THE OUTER SHELL

The lag time of a tablets containing different weight ratio of HPC-EXF: PHARMATOSE® DCL 11 was shortened as compared with that of the tablet of only HPC-EXF with increase in weight ratio of HPC-EXF: PHARMATOSE® DCL 11 from 1 hour to 3 hours. It is well known that the addition of spray dried lactose can improve the flow and bond properties of other excipients during direct compression. In particular, spray dried lactose with higher water solubility might also facilitate the disintegration and dissolution of solid dosage forms. As the relative contents of HPC-EXF was decreased by adding water soluble lactose, strength of the gel matrix would be decreased118, resulting in an increased hydration rate and an increased erosion rate of the outer coating layer. And also slight difference in lag time with change in core tablet was observed.

Formulation F23 to F27 contains HPC-EXF: PHARMATOSE® DCL 11 weight ratio of 87.5:12.5, 75:25, 50:50, 25:75 and 12.5:87.5 respectively.

EFFECT OF GELLABLE MATERIAL (XANTHAN GUM) COMBINED WITH GELLABLE MATERIAL (LOCUST BEAN GUM) IN THE OUTER SHELL

The initial increase in drug release rate on increasing the concentration of xanthan gum can be explained on the basis that a higher binder concentration led to an increase in hardness of the tablet, while the porosity and capillary pore sizes were reduced5. This in turn reduced the wicking of water into the tablet and consequently the swelling and drug release rates are slowed. These tablets showed a considerable swelling at a pH of 6.8 and the drug was dispersed in the swollen matrix formed by the polysaccharide.

Locust bean galactomannan were found to be soluble in water. Cross-linked galactomannan though lead to water-insoluble layer forming product presenting degradation in colonic microflora.116 However, dissolution study performed on theophylline tablets coated with cross-linked galactomannan showed the mechanical unsteadiness of these coatings in the dissolution media117, in that way suggestive of the non appropriateness of such films as colon carriers.

Formulation F28 to F30 shows increase in lag time and decrease in Montelukast Sodium release rate with increase in weight ratio of Xanthan Gum/Locust Bean Gum. Formulation F28 to F30 contains Xanthan Gum/Locust Bean Gum weight ratio of 25:75, 50:50 and 75:25 respectively.

EFFECT OF ERODIBLE MATERIAL (KLUCEL EXF) COMBINED WITH HYDROPHOBIC EXCIPIENTS (DI -TAB®) IN THE OUTER SHELL

When hydrophobic excipients combined with HPC-EXF, the decreased in lag time was also observed with increase in weight ratio of HPC-EXF: DI -TAB®. As DI -TAB® is hydrophobic in nature, it retards the hydration of outer coating layer to the some extent, but once as HPC-EXF hydrates by dissolution medium it starts dissolving and eroded because of compacts formed by HPC-EXF alone is more firm then combination of DI -TAB® with HPC-EXF. Due to rapid hydration and erosion of outer coating layer, no significant effect of core composition observed.

This indicates that both lactose and dicalcium phosphate dihydrates had similar effect on the lag time and release rate of Montelukast Sodium from outer coating layer composed of HPC-EXF. So it can be concluded that hydrophilicity or hydrophobicity of added excipients in the outer core has a little effect on the lag time and release behavior of Montelukast Sodium from outer coating layer. The explanation for the effect of added excipients in the outer shell on the lag time of press-coated tablet was that these excipients reduced the tortuosity of the diffusion path of the dissolution medium and increase the erosion of erodible polymer.

Formulation F31 to F35 contains HPC EXF/ DI- TAB® weight ratio of 12.5:87.5, 25:75, 50:50, 75:25 and 87.5:12.5 respectively.

COMBINATION OF GELLABLE MATERIAL XANTHAN GUM (XG) WITH GELLABLE MATERIAL GUAR GUM (GG) IN THE OUTER SHELL

The formulation S1, S2, S3, S4, S5, S6 and S7 was having mixture of Xanthan Gum and Guar Gum in different weight ratio respectively. The formulation S1 shows lag time more than 24 hours because it contains the press coating of pure Xanthan Gum only. Billa et al.,122 was reported xanthan gum as hydrophilic polymer matrices with uniform drug release characteristics. Because drug release from xanthan gum matrices is proceeded by polymer hydration, processing variables that might affect its hydration would also affect its performance as a controlled release dosage form.

Rama Prasad et al.,123 reported therapeutically guar gum is used as part of the diet of the patients suffering from diabetes mellitus. Krishnaiah et al.,124 studied guar gum on exposure to dissolution fluids gets hydrated and forms a viscous gel layer that slows down further seeping-in of dissolution fluids towards the core of the matrix tablet. The strength of the viscous gel layer around the core of the matrix tablets generally depends on several factors such as particle size, force of compression, presence of other excipients, viscosity of the polymer, solubility of the drug etc.

Ughini et al.,125 guar gum was used as the only retarding polymer, a first-order release kinetic is observed. In an effort to obtain some evidence for the relationship between release mechanism and water uptake and matrix mass loss kinetics, Three processes of water penetration, gelatinization, and diffusion rate have also been reported previously as the rate-limiting steps for the release of water-soluble drugs with first-order release kinetics for guar matrices by Al-Saidian et al.,126 reported a first-order kinetics via Fickian-diffusion for diltiazem HCl release from Guar gum matrix tablets.

Formulation S2 having weight ratio of XG: GG is 87.5:12.5 respectively and it shows lag time upto 8 hours. Formulation S3 shows lag time upto 7 hours because it is having weight ratio of XG:GG is 75:25 respectively. Formulation S4, S5 and S6 having lag time upto 6 hours, 5 hours and 5 hours respectively. And it contains the weight ration of XG: GG are 50:50, 25:50 and 12.5:87.5 respectively. Formulation S7 having lag time upto 6 hours because it contains the press coating of guar gum only.

EFFECT OF AC-DI-SOL LEVEL ON COMBINATION OF ERODIBLE MATERIAL (KLUCEL EXF) WITH RUPTURABLE MATERIAL (ETHYL CELLULOSE) IN THE OUTER SHELL

By combining erodible polymer (HPC-EXF) with rupturable polymer (EC) lag time increases with increasing weight ratio of HPC-EXF/EC. This is only because while combining hydrophilic HPC-EXF with EC; HPC-EXF acts as a binder too. As tablet comes in the contact of dissolution medium HPC-EXF starts hydrating but as EC is hydrophobic in nature it retards the hydration of HPC-EXF and as EC is semi permeable in nature105 dissolution medium penetrates faster in EC coated tablet compared to along with HPC- EXF. As HPC-EXF forms a compact with EC water would not penetrate faster as compared to EC outer coating shell.

But in formulation S8 to S11 all formulations containing the weight ratio of HPC-EXF/EC is same i. e. 50:50. Change is only in the inner core tablet formulation in each formulation. The formulation S8 to S11 containing core tablet formulations A1 to A4 respectively.

Formulation containing Avicel PH 101 as filler binder, Ac-Di Sol as superdisintegrant in the 1% and 2% for formulation A1 and A2 respectively. Magnesium stearate and aerosil used as lubricant and glidant. As the concentration of Ac-Di-Sol increases show decrease in the disintegration time and increase in dissolution of drug. From drug release it was observed that increase in concentration of Ac- Di-Sol increases the drug release upto 2% concentration in the tablet, but further increase in the concentration of Ac- Di-Sol not show any increase in the dissolution rate.

Formulations A3 and A4 were containing Starlac as filler binder, Ac-Di Sol as superdisintegrant in the 1% and 2% respectively. Magnesium stearate and aerosil were used as lubricant and glidant. As the concentration of Ac-Di-Sol was increases show decrease in the disintegration time and increase in dissolution of drug. 100% drug were released from the all the formulation A1, A2, A3 and A4 in 24, 18, 20, 16 minutes respectively. From drug release it was observed that increase in concentration of Ac- Di-Sol increases the drug release. So the formulation S8, S9, S10 and S11 having same lag time upto 6 hours.

COMBINATION OF ERODIBLE MATERIAL (KLUCEL EXF) WITH INERT HYDROPHOBIC MATERIAL (DI-TAB®) IN DIFFERENT WEIGHT RATIO

In order to investigate effect of excipients on the lag time and drug release rate from HPC-EXF, and DI -TAB® (DCP Dihydrate - an insoluble excipient) were chosen.

When hydrophobic excipients combined with HPC-EXF, the decreased in lag time was also observed with increase in weight ratio of DI -TAB®/HPC-EXF. As DI -TAB® is hydrophobic in nature, it retards the hydration of outer coating layer to the some extent, but once as HPC-EXF hydrates by dissolution medium it starts dissolving and eroded because of compacts formed by HPC-EXF alone is more firm then combination of DI -TAB® with HPC-EXF. Due to rapid hydration and erosion of outer coating layer, no significant effect of core composition observed.

This indicates that both lactose and dicalcium phosphate dihydrates had similar effect on the lag time and release rate of salbutamol sulphate from outer coating layer composed of HPC-EXF. So it can be concluded that hydrophilicity or hydrophobicity of added excipients in the outer core has a little effect on the lag time and release behavior of salbutamol sulphate from outer coating layer. The explanation for the effect of added excipients in the outer shell on the lag time of press coated tablet was that these excipients reduced the tortuosity of the diffusion path of the dissolution medium and increase the erosion of erodible polymer.

The order of the time lag changed according to the weight ratio of HPC-EXF/DI-TAB® mixture as follows: S12 (100:00) 5 hours, S13 (87.5:12.5) 3 hours, S14 (75:25) 3 hours, S15 (50:50) 2 hours, S16 (25:75) 2 hours, S17 (12.5:87.5) 1 hour and S18 (00:100) 1 hour.

COMBINATION OF GELLABLE MATERIAL XANTHAN GUM (XG) WITH HPMC K 100M IN DIFFERENT WEIGHT RATIO

Salsa et al128 studied hydration rate of this synthetic polymer relates to its hydroxypropyl substitutes percentage. HPMC-K100M contains the greatest amount of these groups and produces strongly viscose gel that plays an important role in drug release especially at the beginning of the release profile. Therefore, the quick hydration and subsequent gel formation is a foremost and important property of an excipient for it to be used in sustained-release formulations.

Talukdar et al129 reported in respect of controlled drug release behaviour xanthan gum matrices have some important pharmaceutical as well as economical advantages (e.g., absence of initial burst release, higher drug-retarding ability, more reproducibility in drug release, and the possibility of zero-order release kinetics) over HPMC matrices. Considering the influence of ionic strength of the medium on drug release behaviour xanthan gum has a disadvantage that the drug release is influenced by the total salt concentration within the range of gastro-intestinal tract, while the drug release from HPMC matrices is independent of ionic strength. But this ionic strength dependency should not be considered as a total failure of XG for controlling the drug release. Compaction characteristics between the two polymers are quite similar, but the flowability of xanthan gum is better than that of HPMC.

Talukdar et al130 reported drug diffusion in hydrated HPMC matrices is higher than in hydrated xanthan gum matrices. These differences in drug diffusion between the two polymer solutions well explain the reason for previously observed higher ability of xanthan gum than HPMC to retard the release of a drug when they used as matrix forming agent, for controlled-release drug delivery.

The order of the time lag changed according to the weight ratio of XG/HPMC K100M mixture as follows: S19 (87.5:12.5) 8 hours, S20 (75:25) 7 hours, S21 (50:50) 6 hours, S22 (25:75) 6 hours, S23 (12.5:87.5) 6 hours and S24 (100:00) 7 hours.

EFFECT OF DIFFERENT HPMC GRADES ON DRUG RELEASE PROFILE FROM COATED TABLETS

Wan et al.131 studied release mechanism of drug through hydroxypropylmethylcellulose (HPMC) matrices, showed that the normalized increase in matrix thickness after 30 min of swelling for HPMC matrix tablets was higher for higher molecular weight HPMC grades. They attributed this to the larger hydrodynamic volume occupied by higher molecular weight chains when hydrated. As the polymer chains become more hydrated and the gel becomes more dilute, the 'disentanglement concentration' may be reached, that is, the critical polymer concentration below which the polymer chains disentangle and detach from a gelled matrix. The polymer will then undergo simultaneous swelling, dissolution and diffuse into the bulk medium resulting in erosion of the polymer.

Hypromellose acetate succinate is commonly used in oral pharmaceutical formulations as a film coating, as well as enteric coating material for tablets or granules.132, 133, 134 It is insoluble in gastric fluid but will swell and dissolve rapidly in the upper intestine. For aqueous film coating purposes, a dispersion of hypromellose acetate succinate fine powder and triethyl citrate (as a plasticizer) in water is commonly utilized.135, 136, 137 Organic solvents can also be used as vehicles for applying this polymer as a film coating. Hypromellose acetate succinate may be used alone or in combination with other soluble or insoluble binders in the preparation of granules with sustained drug-release properties; the release rate is pH-dependent. Dispersions of poorly soluble drugs with hypromellose acetate succinate are prepared using techniques such as mechanical grinding, solvent evaporation, and melt extrusion.138, 139, 140, 141, 142

The order of the time lag changed according to the weight ratio of HPC-EXF/DI-TAB® mixture as follows: S25 (100:00) 7 hours, S26 (100:00) 3 hours, S27 (100:00) 5 hours and S28 (100:000) 6 hours.

EFFECT OF DIFFERENT EUDRAGIT GRADES ON DRUG RELEASE PROFILE FROM COATED TABLET

Eudragit L100 and S100 types are used as enteric coating agents because they are resistant to gastric fluid. Different types are available that are soluble at different pH values: e.g. Eudragit L is soluble at pH > 6; Eudragit S and FS are soluble at pH > 7.

The order of the time lag changed according to the coating of different eudragit grades are as follows: S29 (100:00) 5 hours and S30 (100:00) 4 hours.

EROSION STUDY OF PRESS COATED TABLET

Upon increasing weight ratio of EC/HPC-EXF lag time of all subsequent formulations increases and % erosion of tablet decrease, this was just because EC is hydrophobic in nature it would not erode but as HPC-EXF present in it get dissolved and eroded. In formulation containing Starlac® as a filler in core tablet, drug get released when almost complete outer coating shell get eroded, while in formulation containing avicel® as a filler in core tablet drug get release when sufficient internal pressure generate in the core rather than complete erosion of outer coating layer. When formulation shows increase in lag time upon increases in weight ratio of EC/HPC-EXF, the difference was in comparative delay in lag time and greater % erosion. This is because of core tablet present in these formulations were not generate sufficient to internal pressure two broke the outer coating layer at same time point as in case with formulations. And finally it takes more time to get release of drug and % erosion of outer coating layer increases.

Upon increasing weight ratio of HPC-HF/HPC-EXF lag time increases and erosion of final tablet depends upon the lag time of tablet. This is because the Ac-Di-Sol® present in core tablet generate sufficient pressure to broke the outer coating layer, while in formulations, drug get released only when complete erosion of outer coating layer take place. While different correlation of lag time and % erosion of tablet observed in formulations. This is because further increase in weight ratio of HPC-HF/HPC-EXF forms a tight gel structure and the pressure generated in core tablet of formulations were not sufficient to broke the outer coating layer. And also the fillers (avicel®) present in the core tablets of formulations retards the hydration of core. And drug gets only released when dissolution medium completely hydrates the core tablet, this would take long time as compared to formulation containing C1 core tablets.

While Starlac® present in the core tablet of formulations gives rapid drug release by diffusion from the formed gel structure because of concomitance effect of hydration and disintegration of Starlac®.

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