INTRODUCTION:

A significant proportion of the populations such as pediatrics and geriatrics have difficulty in swallowing solid oral dosage forms. This problem becomes more acute for the administration of extended action dosage forms due to the increase in volume of the delivery system. An oral pharmaceutical suspension presents a novel means of circumventing the potential problems associated with the administration of such systems¹. The incorporation of extend release technology in the oral suspension drug delivery system provides improvement in the rate and extent of drug absorption, higher patient compliance, reduction of side effects and taste masking for bitter drug^2,3. Extended release dosage forms are allows at least a twofold reduction in dosage frequency as compared to that drug presented as an immediate release form⁴.

Ambroxol HCl is used as a mucolytic, while Guaifenesin increase the volume and reduce the viscosity of tenacious sputum and is used as an expectorant for productive cough. Both drugs are present together in pharmaceutical dosage forms for the treatment of cough.

Ambroxol is a secretolytic agent used in the treatment of respiratory diseases associated with viscid or excessive mucus⁵. Ambroxol is indicated as "secretolytic therapy in bronco pulmonary diseases associated with abnormal mucus secretion and impaired mucus transport. It promotes mucus clearance, facilitates expectoration and eases productive cough, allowing patients to breathe freely and deeply"⁶. Its usual dose is 15-30 mg 3-4 times daily⁷.

Guaifenesin is an expectorant, a drug which increases respiratory tract fluid secretions and helps to loosen phlegm and bronchial secretions. The increase flow of less viscous secretion promote ciliary action and fascinates the removal of mucus hence expectorant such as Guaifenesin changes dry unproductive cough to one that is more productive and less frequent⁸. Guaifenesin is known chemically as 3(2-methoxyphenoxy)-1,2-propanidiol, crystalline powder soluble in water and alcohol. Guaifenesin is readily absorbed from the intestinal tract and is rapidly metabolized and excreted in urine but has a short plasma half-life of one hour because of the rapid metabolization and excretion of Guaifenesin⁹. The commonly prescribed dosage for 12years and elder are 200 to 400mg every 4 hrs not to be exceeded than 2.4mg/day¹⁰. Ion exchange resin technology can be used for the extended release drug delivery to reduce the dosing frequency and for taste masking of bitter drug that improves the patient compliance¹¹. Dowex50 I is ion exchange resin polymer used to prepare the drug and ion exchange resinate¹². Ethylcellulose is widely used coating polymer in pharmaceuticals in extended drug delivery system as it offers numerous advantages such as improved efficiency, reduced toxicity and improved patient compliance¹³. Then, these resonates were formulated in to a suspension form, which can release the drug in a slow and controlled manner. The polymers used for microencapsulation of drug resonates adversely affects the rate of drug release from microspheres¹³. In the present work, Ambroxol HCl and Guaifenesin were absorbed on cationic exchange resin, dowex50 and a coating of Ethylcellulose was given to retard the drug release. Hence the present work is aimed at development and formulation of extended release suspension with suitable concentration of Ethylcellulose in Ambroxol HCl and Guaifenesin microcapsules.

MATERIALS AND METHODS:

The materials used in the study are Ambroxol HCl, Guaifenesin, Dowex50, Ethylcellulose, Xanthum gum Sodium Carboxy-methyl Cellulose, Sorbitol syrup, Vanilla tincture, Chlorophyll. Ambroxol HCl, Ethylcellulose were gifted from Indoco Remedies, Mumbai, Guaifenesin was obtained from Granule, India where as Dowex50 was purchased from Sigma Aldrich Germany. All the other chemicals used were of analytical grade.

Resin purification:

Resin requires purification treatment to remove the impurities associated during its industrial manufacturing^{14, 15}. The dowex50 resin purification method was done by the method described by Irwin et al. 1987¹⁶. The resin was washed three times with distilled water, followed by successive washing with 95% ethanol, 50% ethanol, and distilled water to remove color impurities. Alternatively the resin was purified by 2M NAOH and 2M HCL respectively and washed several times with distilled water. The activated resins were dried at 50 ^°C in a hot air oven for 12 hrs. The resin in hydrogen form was evaluated for moisture content, particle size and cation exchange capacity.

Preparation of drug and resin complexes:

The preparation of Ambroxol HCl and Guaifenesin drug resin complex was done by batch process, using the method described by Jeon and Park¹⁷. Previously purified and activated resin dowex50 were dispersed in solution of accurately weighted quantity of Ambroxol HCl and Guaifenesin in solvent (mixture of methanol and water in the proportion of 1:1). This mixture was stirred for 24 hours on a magnetic stirrer to reach the equilibrium the complex was separated from the supernatant by vacuum filtration. The Ambroxol HCl, Guaifenesin and resinate complex is then filtered through Whatman filter paper. The drug resinate complex is washed several times with de-ionised water to remove the traces of drugs and dried at 50^°C. The time required for maximum drug loading was determined spectrophotometrically.

Evaluation and characterization of drug resinate complex:

The resonates complex of Ambroxol HCl and Guaifenesin prepared was then evaluated for different physicochemical properties such as moisture content, drug content, flow properties and in vitro drug release¹⁸.

Drug content in resonates complex:

The drug content in the drug-resinate complex is determined by placing 50mg of drug-resinate in a beaker in which 50ml of 0.1M HCl was added for eluting the Ambroxol HCl and Guaifenesin from the resinate. The solution in the beaker was then sonicated for 20 min and again stirred for 2 hrs on magnetic stirrer after complete extraction of the drug. The amount of the drug was quantified using a spectrophotometrically method at 245nm and 274 nm for Ambroxol HCl and Guaifenesin respectively in the presence of blank prepared from microspheres containing all material except drug¹⁹.

Drug loading analysis:

Drug loading was found to increase with increasing fraction of resin but it is upto some extent 1:1 ratio showed maximum loading after that decrease in drug loading was observed.

In vitro drug release:

USP dissolution test apparatus type I i.e. basket type at 100 rpm is used to perform the characteristic In vitro drug release study of Ambroxol HCL and Guaifenesin drug-resonate complex. In vitro study was carried out using 900 ml of dissolution medium at 37 ± 0.5^°C. The pHof the buffer was 1.2 for first two hours and pH 7.2 buffer for next six hours. A 5ml sample of solution was withdrawn from the dissolution apparatus per hour and the samples were replaced by fresh dissolution medium then the samples were filtered and absorbency were measured at 245 nm and 274nm using UV/Visible spectrophotometer for Ambroxol HCL and Guaifenesin respectively^{20, 21}.

Preparation of polymer coated drug resinate complex:

The microencapsulation of drug-resinate was carried out by spray drying technology. Ethylcellulose is used to further retard the drug release from the complex. The drug resinate complex was suspended in various polymer solution of different concentration of Ethylcellulose with constant magnetic stirring, then subsequently spray dried in laboratory spray dryer through a two fluid pressure nozzle with a concurrent drying air flow²².

The operating conditions were-

Inlet air temperature : 55 to 60^°C

Feed spray rate : 3.0 ml /min

Aspirator position : 10

Spray flow : 400 to 500nl /hrs

Outlet temperature : 40^°C

The formulation adopted after preliminary experiments was as follows ²³-

Polymer	Concentration of polymer			Solvent
Ethylcellulose	5%	10%	15%	Methylene Chloride

Evaluation and characterization of Ambroxol and Guaifesin resin microencapsules:

Scanning electron microscopy:

The scanning electron microscope is used to study the microscopic appearance of drug- resinate complex and its microcapsules. The sample was coated with gold before scanning (Figure 1).

FIGURE 1: SEM IMAGE OF MICROENCAPSULATED AMBROXOL HCl AND GUAIFENESIN RESINATE BEADS

Determination of extent of coating polymer of microcapsules:

One hundred milligrams of microcapsules was accurately weighed and washed three times with 10 ml acetone in order to remove the coating. The remaining Ambroxol HCl and Guaifenesin resin where dried at 50 ^°C for 12 hours and weighed. The percentage coating polymer was calculated by following formula²⁴

Coating extent = (Drug resin microcapsules wt. − Dried resin beads wt.)/Drug resin microcapsules wt. × 100

In vitro drug release study from prepared microcapsules:

In vitro drug release from the prepared microcapsule was performed by USP dissolution test apparatus i.e. basket type at 100 rpm. In vitro study was carried out using 900 ml of dissolution medium at 37 ± 0.5^°C. The pHof the buffer was 1.2 for first two hours and pH 7.2 buffer for next six hours. A 5ml sample of solution was withdrawn from the dissolution apparatus hourly and the samples were replaced by fresh dissolution medium then the samples were filtered and absorbency were measured at 245 nm and 274nm using UV/Visible spectrophotometer for Ambroxol HCL and Guaifenesin respectively ( figure 2).

FIGURE 2: IN VITRO DRUG RELEASE FROM COATED MICROCAPSULES

Formulation of extended release suspension of Ambroxol HCL and Gauifenesin:

To study the effect of the different concentration of Ethylcellulose used for coating of drug-resinates complex on in vitro drug release profiles of extended release suspension prepared by microencapsulated drug-resinate complex three batches with varying Ethylcellulose concentration is prepared. 0.4% Xanthum gum and 0.8% Sodium Carboxy Methyl-cellulose is used as suspending agent, simple syrup and Sorbitol syrup70% is used as sweetening agents. Deionised distilled water as vehicle. The concentration of microencapsulated resinate was taken in a concentration such that each 10ml of prepared suspension will deliver 60 mg of Ambroxol HCl and 600mg of Guaifenesin. To improve the physical stability of suspension methylparaben and propylparaben were used as preservatives. To have better palatability and appearance of suspension vanilla tincture in the concentration of 0.2 ml was added to enhance the flavor and chlorophyll in the concentration of 0.001% w/v are used as coloring agent to impart the color.

Evaluation of prepared extended release suspension:

The prepared extended release suspension was then evaluated for different test such as pH, sedimentation volume, particle size, redispersibility, viscosity. The results are as shown in Table 2.

Determination of drug leakage from prepared suspension:

The drug was stored at room temperature for one month to study the amount of drug leaching in to the vehicle of suspension an aliquot of 1 ml was withdrawn from the suspension for drug leaching studies from suspended microcapsules during storage The aliquot was filtered and the microspheres washed with water to remove the suspending vehicle and then dried in oven at 37^°C for 24 h. Dried microspheres were dissolved with ethanol. The dissolved drug amount was measured spectrophotometrically at 245 nm and 274nm.

In Vitro release study of suspension:

In vitro drug release from the prepared suspension was performed by USP dissolution test apparatus i.e. basket type at 100 rpm. In vitro study was carried out using 900 ml of dissolution medium at 37 ± 0.5^°C. The pHof the buffer was 1.2 for first two hours and pH 7.2 buffer for next six hours. A 5ml sample of solution was withdrawn from the dissolution apparatus hourly and the samples were replaced by fresh dissolution medium then the samples were filtered and absorbency were measured at 245 nm and 274nm using UV/Visible spectrophotometer for Ambroxol HCL and Guaifenesin respectively (Figure 3).

FIGURE 3: IN VITRO DRUG RELEASE FROM EXTENDED RELEASE SUSPENSION

RESULT AND DISCUSSION:

Ambroxol HCl and Guaifenesin microcapsules extended release suspension are prepared. To study the extended release of the drug and increase in the half life of drug three batches of suspension with different concentration of microencapsulating polymer Ethylcellulose and drug-resinate in the ratio (5-15%) is used. In this study the microsphere with 1:1 drug ion exchange polymer ratio is selected for suspension formulations as they are having suitable drug loading efficiency and good micromeritics. SEM images of microspheres (Figure 1) showed that the microspheres were spherical with a smooth surface. The drug loading capacity of an ion exchange resin and uniformity of drug content was found satisfactory. The prepared microcapsules were then evaluated for percentage yield, drug content, particle size, and in vitro drug release. The particle size values for all the formulation were comply as per I.P. requirements. The drug content for all the formulation was found to be in between the values of 96-98 %. The microencapsules are evaluated for different physicochemical properties and results are found satisfactory for preparation of suspension. The values are shown in (Table 1).

All the batches are manufacture at the similar condition to avoid the processing variables. The prepared suspension was then evaluated for different physicochemical properties such as pH, sedimentation volume, redispersibility, viscosity, sedimentation volume, drug leaching and in vitro drug release studies. The data obtained from results of in vitro drug release profile of different batches of suspensions revealed that increase in ethylcellulose concentration reduces the rate of drug release. The batch F3 in which maximum concentration of ethylcellulose used showed the minimum drug release at the end of 8 hrs. Batch F1 in which minimum concentration of polymer is used showed the maximum drug release. Among the different batches formulated batch F2 with 10 % ethylcellulose -drug resinate have uniformity of drug release at the end of 8 hrs and is used as ideal formulation for extended release suspension. The results of pH particle size, wt/ml, sedimentation rate, Redispersibility, viscosity drug content and in vitro drug release pattern are shown in table 2.

TABLE 2: EVALUATION OF SUSPENSION

Parameter	Batch Number
Parameter	F1	F2	F3
Appearance	Uniform	uniform	Uniform
Taste	Sweet, palatable	Sweet, palatable	Sweet, palatable
Ph	6.01 ±0.02	5.98±0.02	5.96±0.02
Viscosity(cps)	215	227	312
Sedimentation ratio	0.97	0.94	0.91
Particle size(um)	80-197	73-191	67-188
Redispersibility	+ + +	+ + +	+ + +
Drug content (% w/v)	95.24	98.07	96.22
In vitro dissolution (%)	91.81	90.12	96.22
Drug eluted in vehicle	0.38	0.33	0.27
wt./ ml	1.29	1.22	1.30

The suspension was placed for the accelerated Stability studies. Suspensions were packed in 60 ml glass bottle. The packed bottles paced in stability chamber and stored at various temperature 37^°C, 45^°C and 60^°C for three month samples were collected at 0, 5, 15, 30, 60, 90 days and evaluated for various parameters that can be changed during storage such as viscosity, pH, drug content, redispersibility, taste and microbial growth there was no considerable change in the formulation after three month. Thus the formulation containing microcapsules suspension was found to be stable.

CONCLUSION:

A novel extended release formulation of Ambroxol HCl and Guaifenesin with satisfactory drug release was prepared. Suspension prepared from Ion exchange resinate of Ambroxol HCl and Guaifenesin coated with ethylcellulose and SCMC-Xanthum gum as suspending agent have efficient physicochemical stability and sufficient drug release profile and can be suitable dosage form for geriatrics and pediatric use.

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Received on 20.10.2011 Modified on 08.11.2011

Research J. Pharm. and Tech. 5(1): Jan. 2012; Page 98-102

Batch no.	Drug resinate polymer ratio	Nature of Microcapsule	Drug content (%)	Average particlesize (um)
F1	5	Free Flowing	95.24	50-130
F2	10	Free Flowing	98.07	63-144
F3	15	Free Flowing	97.34	80-162