FORMULATION AND IN VITRO EVALUATION OF EZETIMIBE RAPIDMELTS

Objective: The main objective of the present research was formulation and evaluation of ezetimibe rapidmelts. Results: Rapidmelts prepared using direct compression and sublimation methods were evaluated for weight variation, hardness, friability, % drug content, and disintegration time. The best formulation was subjected to stability testing for 6 months at 25°C/60% RH and 40°C/75% RH. All the prepared formulations compiled with the pharmacopeial limits. In all the formulations, results suggest that E12 formulation has given the best results. Conclusion: From the result, it was concluded that rapidmelts prepared using sublimation method which has given better result than direct compression method. That final formulation was further evaluated for in vivo studies using rabbits.


INTRODUCTION
Oral route of administration is one among the foremost convenient route for drug administration. As per USFDA, rapidmelts were defined as "A solid dosage form containing a medicinal substance or active ingredient which disintegrates rapidly when placed upon the tongue within a matter of seconds" [1]. After disintegration, the drug solution is often partially or completely absorbed by the sublingual blood vessels and bypasses first-pass metabolism by the liver or be absorbed from the gastrointestinal tract after swallowing. Prescription rapidmelt products initially were developed to beat the problem in swallowing among pediatric and geriatric populations who have difficulty in swallowing conventional tablets and capsules [2].
Nowadays, rapidmelts are going to be more widely available as overthe-counter products for the management of the many conditions such as lowering cholesterol, heart problems, allergies, and cold. The presence of a highly porous surface with in the tablet matrix is that one among the key factors for the rapid disintegration of oral disintegrative tablet. Many methods were reported for solubility and dissolution enhancement of poorly soluble drug such as micronization, complexation, solid dispersions, and kneading method. Solid dispersions are a way that depends on melting or dissolution process to disperse one or more active ingredient during in a carrier or matrix with in the solid state. This ensures increased drug wettability and reduction of particle aggregation and hence increased drug dissolution [3].
Pediatric and geriatric patients will face many difficulties in swallowing or chewing pharmaceutical dosage forms for oral administration. Tablets that rapidly dissolve on contact with buccal cavity could present an answer to those problems then there is an increased interest fastdissolving dosage forms for buccal, sublingual, and oral administration.
Fast-dissolving/disintegrating tablets are ideal fit to those patients as they immediately release the active drug when placed on the tongue by rapid disintegration [4]. Hence, with in the present investigation, rapidmelts of ezetimibe were prepared.
The drug ezetimibe was widely utilized in the treatment of hyperlipidemia. It acts as a cholesterol absorption inhibitor. Hyperlipidemia drugs are mainly want to reduce cholesterol levels in patients in danger of disorder. Ezetimibe is practically insoluble in water and crystalline compound. For oral absorption, dissolution is thus the rate limiting step. To reinforce the bioavailability improvement in solubility and dissolution rate are essential.
As ezetimibe comes under BCS Class II drug, solid dispersions of ezetimibe were prepared using different polymers in several ratios using different techniques to reinforce the solubility of the drug. Solid dispersions were formulated as rapidmelts using different superdisintegrants using direct compression method. To enhance the porosity, volatile substances like subliming agents are often utilized in tableting process, which sublimated from the formed tablet. Ezetimibe rapidmelts were prepared using direct compression and sublimation techniques.

Calibration curve for ezetimibe
For the preparation of ezetimibe stock solution. For the stock solution, ezetimibe 10 mg was taken and dissolved in few ml of methanol. The stock solutions were diluted with methanol to organize the concentrations 5, 10, 15, 20, and 25 µg/ml of ezetimibe. They were analyzed by UV-visible spectrophotometer at 233 nm using methanol as blank. A calibration curve was plotted against concentration and absorbance.

Preparation of solid dispersions Solvent evaporation method
For the preparation of solid dispersions, drug and polymers were mixed in a mortar with ratios (1:0.5, 1:1, and 1:1.5). Ethanol was added in proportion wise with constant and continuous stirring until the mixture was completely dissolved. Ethanol was evaporated under constant stirring and resultant solid dispersions were collected (Table 1).

Kneading method
In a mortar, 50% of solvent was taken there to add calculated amount of polymer and is triturated to urge slurry-like consistency. Then, the drug was incorporated, remaining solvent was added, and trituration is sustained for 1 h, air-dried at 25°C for 48 h, and therefore, the resulting dried product was pulverized and skilled mesh sieve ( Table 2).

Evaluation of solid dispersions Drug entrapment efficiency
Each solid dispersion about 10 mg was weighed and placed in glass Stoppard tubes and redispersed in 3 ml water. The dispersion was then lysed with 1 ml chloroform to permit for complete release for entrapped drug. Complete extraction of the drug was done by shaking the tubes for 6 h in water bath shaker at 37°C. The centrifugation of the samples was done at 6000 rpm for 5 min and then allowed to face for complete separation of the two phases. The collected aqueous solutions were analyzed for determining the drug concentration as previously described (Table 3). Drug concentration was also used for determining % encapsulation efficiency consistent with the subsequent formula. % Encapsulation efficiency = (Actual drug loading/Theoretical drug loading) × 100.

Drug entrapment for solid dispersions
Among both the methods, cosolvent evaporation was found to be entrapped good compared to kneading method.

Preparation of ezetimibe rapidmelts
Ezetimibe rapidmelts were prepared using direct compression and sublimation methods.

Direct compression method
In direct compression method supported entrapment values 69.6 mg of solid dispersions which was taken equivalent to 10 mg of drug ezetimibe. Formulation of rapidmelts was done using superdisintegrants croscarmellose sodium, crospovidone, and starch 1500 in concentrations of 2, 4, and 6%. All the ingredients were skilled through the mesh. Then, all the ingredients were mixed in geometric order, and therefore, the tablets were compressed with 8 mm size round punch (Table 4).

Sublimation method
Rapidmelts of ezetimibe were prepared using subliming agents such as camphor, urea, and ammonium bicarbonate in concentrations of 2.5, 5, and 7.5% from the ultimate tablet weight. Accurately weighed amounts of ingredients were thoroughly mixed and compressed into 200 mg tablets using single punch machine of 8 mm round punch and die set. Ezetimibe tablets were then placed in an oven at 40°C till a continuing weight is obtained ( Table 5).

Evaluation of ezetimibe rapidmelts Pre-compression parameters
The various characteristics of blends to be conducted before compression are as follows:

Angle of repose
The fixed funnel method was used to decide the angle of repose. The funnel height was adjusted in such how that the tip of the funnel just touched the apex of the heap of the granules. The granules were allowed to flow onto the funnel freely onto the surface. The peak and diameter of the granular cone was measured and angle of repose was calculated.
Bulk density and tapped density An appropriate amount of powder from each formulation was taken and was introduced into the 10 ml measuring cylinder. After measuring initial volume, the cylinder was allowed to fall into its own weight onto a tough surface from a height of 2.5 cm at 2 s intervals. The tapping of the measuring cylinder was continued until there is no further change in volume which was noted.
Bulk density = Weight of the powder/Bulk volume of the powder Tapped density = Weight of the powder/Tapped volume of the powder Carr's index: The Carr's index was used to measure the compressibility index of the powder blend.
Carr's index = (Tapped density−Bulk density/Tapped density) × 100 Hausner's ratio: Using the bulk and tapped density, Hausner's ratio of ezetimibe blend powder formulation was calculated and it's expressed as: Hausner's ratio = Tapped density/bulk density.  Quantity sufficient for paste formation

Post-compression parameters Hardness
The typical breaking strength of tablets was decided by tablet hardness tester (Monsanto hardness tester). Ten tablets from each formula were tested for its hardness. The mean hardness (±SD) of every formula was determined.

Weight variation
Weight variation test was administered to ensure the uniformity of tablets. From each formulation, 20 tablets were randomly selected and separately weighed. Their average weight was calculated.

Friability
Ten tablets from each batch were collected to the gauge evaluate the friability. The tablets were placed in the Roche friabilator and subjected to 25 rpm for a period of 4 min. Then, the tablets were dusted and once more reweighed. The percentage loss in weights was calculated and taken as a measure of friability.

Wetting time
Five circular tissue papers of 10 cm diameter were placed during Petri dish with a 10 cm diameter. A tablet was placed on the surface of tissue. The time required for water to reach the upper surface of the tablets was noted as the wetting time. The wetting time of the formulations was measured in seconds.

In vitro disintegration time
Disintegration test apparatus was used to measure the in vitro disintegration time. One tablet was placed in each of the six tubes of the basket assembly of the disintegration apparatus and then disk was placed on to each tube. This assembly was then suspended during a 1 L beaker containing water with its temperature being maintained at 37±2°C. The basket was then moved up and down through a distance of 5-6 cm, at the frequency of 28-32 cycles/min. The time required for the complete disintegration of the tablet was noted.

In vitro dissolution studies
The dissolution profiles of ezetimibe from rapidmelts were determined in a dissolution tester, apparatus II. All tests were conducted in 900 ml phosphate buffer pH 7.0 containing 0.5% SLS at a temperature of 37±0.5°C with a paddle rotation speed at 50 rpm. Samples were collected at specified time intervals 1, 5, 10, 15, 20, 25, 30, 35, 40, 45, and 50 min. A 5 ml of dissolution medium was replaced with an equal volume of medium to take care of a constant total volume. Samples were filtered through a 0.45 µm Millipore filter and assayed for drug content spectrophotometrically at 233 nm.

Fourier transform infrared (FT-IR) studies
The concentration of the sample in KBr should be within the range of 0.2-1%. The pellet is far thicker than a liquid film, hence, a lower concentration within the sample is required (Beer's law). The infrared IR beam is absorbed completely or scattered from the sample which ends up in very noisy spectra.

Differential scanning calorimetry (DSC)
DSC was used to evaluate drug-excipient compatibility. The endotherms of pure drug and optimized formulation were recorded separately. The DSC thermograms are obtained by a DSC (DSC 220C, Seiko, Japan) at a heating rate of 10°C/min from 10 to 200°C with in the nitrogen atmosphere.

Stability studies
To review the steadiness of the rapidmelts, representative samples of the were packed in amber colored airtight glass containers and that they were stored in stability chambers maintained at 25°C/60% RH and 40°C/75% RH. The physicochemical properties of those samples were analyzed at 0, 3, and 6 months. From the respective storage conditions at each time point, one formulation was taken out and subjected to content uniformity and dissolution rate studies.

Pre-compression parameters
The values of angle of repose were found to be within the range of 25-30°C bulk densities and tapped densities of varied formulations were found to be within the range of 0.30-0.70 (g/cm 2 ). Carr's index was found to be within the range of 14-25%. The Hausner's ratio was within the range of 1.15-1.35. From the result, it had been concluded that powder blends have good flow properties.

Post-compression parameters
Hardness of all the formulations was found to be within the range of 3-4.5 kg/cm 2 . It indicated that each one of the formulations possesses sufficient mechanical strength. Weight variation was found to be in the range of IP limits. Rapid melts were evaluated for their % friability using   Drug content values for the all formulations were found to be within the IP standards (not <95% and not more than 105%) (Tables 6-11).

In vitro drug release studies
The values are shown in Tables 10 and 11. Formulations from E1 to E9 were prepared using superdisintegrants (CCS, CP, and SSG) by direct   compression method. E10-E18 were prepared using subliming agents (camphor, urea, and ammonium bicarbonate). In direct compression method, superdisintegrants will act by swelling of the drug and it leads to faster disintegration and dissolution. In sublimation method, subliming agents will act by increasing the porosity of drug results in faster wetting and dissolution and bioavailability. Among all the formulations, E12 (camphor 7.5%) has given better dissolution compared to all the formulations. Hence, E12 formulation was selected as optimized as 100% drug release in 5 min.

Stability studies
Hence, based on evaluation parameters and drug release profiles, E12 was selected as optimized and subjected to stability studies and stored at 25°C/60% RH and 40°C/75% RH. The samples were withdrawn at 0, 3, and 6 months, and therefore, the ezetimibe rapidmelts were found to be stable. The amounts of ezetimibe (%) in the rapidmelts stirred under conditions consistent with ICH guidelines are given in

CONCLUSION
Rapidmelts are also known as oral disintegrating tablets (or) fastdissolving tablets. These are mainly intended to be placed in the oral cavity where they dispersed before being swallowed. This is the promising dosage form for the use in pediatrics and geriatrics. The rapidmelts will provide accurate dosing and show good chemical and physical stability with lower doses. The present study was done on rapidmelts of ezetimibe using direct compression and sublimation methods. As ezetimibe comes under BCS Class II, solubility of ezetimibe was enhanced by preparing solid dispersions. The prepared solid dispersions were formulated as rapidmelts using direct compression method. In the sublimation method, rapidmelts were prepared using subliming agents. The prepared blends were evaluated for

Rani and Muzib
pre-compression studies such as bulk density, tapped density, Carr's index, Hausner's ratio, and angle of repose. They were found to be within limits. After completion of pre-compression studies, required powder blend was weighed and compressed using tablet compression machine. They were kept for post-compression studies such as weight variation, hardness, friability, in vitro disintegration, and dissolution studies. From dissolution studies, rapidmelts prepared using camphor (7.5%) which has given maximum drug release within 5 min. Hence, it was concluded that rapidmelts prepared using sublimation method which has given better result than direct compression method. Hence, sublimation method would be an effective method for the preparation of rapidmelts.

ACKNOWLEDGMENT
This article does not contain any studies with human and animal subjects performed by any of authors. Authors wish to thank the Sri Padmavathi Mahila University for providing necessary facilities to carry out research work.

AUTHORS' CONTRIBUTIONS
We here with to submit a manuscript entitled: "Formulation and In vitro evaluation of ezetimibe rapidmelts" author by Neelimarani. T and Indira Muzib. Y for the consideration for the journal as a research paper in the journal Asian Journal of Pharmaceutical and Clinical Research. Neelima Rani Tumma analyzed the laboratory work, analyzed the data, and wrote the manuscript. Both the authors read and approved the manuscript. All authors are the guarantors.