Taste Masking of Tinidazole and Optimization of Microencapsulation Method

Kshirsagar S. J

Tinidazole was microencapsulated within various cellulose polymers like Ethyl
cellulose, Eudragit – L & Cellulose Acetate Phthalate (CAP) with the final
aim to mask its taste without affecting its bioavailability.

The Microspheres were prepared using the solvent evaporation technique. The
contribution of different variables like polymer type, drug polymer ratio, stirring
speed, polymer solution concentration, surfactant concentration and type of
the surfactant on microencapsulation of Tinidazole were examined. Reconstitutable
suspension of microencapsulated Tinidazole was formulated comprising of 1:2
drug polymer ratio.

The results demonstrated that the use of CAP as embedding polymer gave good
yield and drug content, suitable particle size and sphericity for suspension
formulation and hence was selected for further work. Drug polymer ratio of 1:2
gave good quality spherical microsphere. It was found that stirring speed; polymer
solution concentration, type and concentration of emulsifier all had a profound
influence on the product obtained. In order to minimize the leaching of drug
from micro sphere a stable reconstitutable suspension was formulated. From the
organoleptic evaluation of Tinidazole microsphere it was concluded that microencapsulation
is the effective method of taste masking of Tinidazole.

Introduction

The problem of providing patient with drug dosage forms that are palatable
has been around for long time. The problem of orally taking drugs
of bitter nature type is more prevalent in pediatric and geriatric patient than
in normal adults. There are number of methods available for taste masking of
drugs like use of taste masking agent, solubility limiting method¹,
complexation with ion exchange resins, complexation with cyclodextrin, microencapsulation,
multiple
emulsion, vesicles and liposome’s ^2-5 Tinidazole, is a orally
absorbed drug used in the treatment of intestinal protozoal infection. Tinidazole
is rapidly absorbed followed by oral administration having T½ of 12 hrs⁶.
Being a highly bitter drug Tinidazole posses a challenge particularly in the
formulation of a pediatric dosage from, for the present study microencapsulation
was selected as the method as for taste masking the bitter taste of Tinidazole.

Microencapsulation has utilitarian value in taste masking where small drug particles can be coated with polymer. These small coated particles can be readily formulated into the aforementioned dosage forms. When the dosage form is placed in the mouth as liquid or masticated with a chewable table, the polymer coated drug cannot contact the taste buds in the mouth and hence objectionable taste of bitter drug is eliminated. A large number of bitter drug have been microencapsulated such as Cefuroxime axetil with cellulose acetate phthalate and hydroxyl propyl methyl cellulose 55 ⁷, Flucoxacillin with ethyl cellulose ⁸, Clarithromycin with amino alkyl – methylacrylate – polymer E⁹,

Beclamide with gelatin ¹⁰ and many more drugs like Acetaminophen & Naproxen⁴.

Among the numerous microencapsulation methods. The solvent evaporation method was selected for the preparation of Tinidazole microsphere. The technique affords easy, cost effective manufacture of microsphere with a relatively high drug loading. Appropriate combination of starting materials and other additives were selected and varied along with different variables to produce Tinidazole microspheres of suitable composition, morphology and drug release characteristics.

The microcapsules were formulated into Reconstitutable suspension and the stability study of suspension was carried out.

Therefore, the present study was under taken to determine the influence of
formulation variables on the micromeritic properties (drug content, particle
size and shape) of the prepared microspheres and ability of microencapsulation
for taste masking of the bitter taste of Tinidazole without affecting its bioavailability.    

Materials & Methods

 Materials:

Tinidazole (Macleod’s Pharmaceuticals), Ethyl Cellulose (Loba chemie Pvt. Ltd.) Cellulose Acetate Phthalate (Colorcon Asia Pvt. Ltd.) Edudragit – L (Rohm Pharma), Heavy liquid paraffin (Loba Chemie Pvt. Ltd) Acetone (Merck), Dichloromethane (Qualigens), Chloroform (Pure Chem.), Petroleum ether (Pure Chem.) Span 80 (Burgoyne Burbridges), Span 85 (Bombay Research Lab), Carboxymethyl Cellulose, Microcrystalline Cellulose (Modern Chemical Production), Tween 80 (Bombay Chemical Research).

All other Chemicals and solvents were analytical grade and were used as received.

Method of microencapsulation:

Microcapsules were prepared by modified emulsion solvent evaporation technique,
in the water in oil technique polymer was added to acetone in a glass vessel
.Tinidazloe was added to above mixture and this mixture was stirred in liquid
paraffin at 10-05C for 1 hour and then at room temperature for 3
hrs. During this time acetone used as solvent of polymer was evaporated. Then
petroleum ether was added & microspheres were separated by filtration &
washed with small quantity of 0.1N Hydrochloric acid to remove Tinidazole on
microsphers outer surface & then allowed to dry at room temperature.

Experimentation:

 In this study three polymers were tried viz. Ethyl cellulose,
Eudragit – l, Cellulose acetate phthalate (CAP) with same drug
polymer ratio (1:2) and stirring speed (1200 rpm) it was found that percentage
yield and drug content of microcapsules are not affected by polymer type, however
microspheres are not affected by polymer type, microspheres with Ethyl cellulose
give irregular shape microsphere, with Eudragit – L size of microsphere was
more as compare to microsphere with CAP. So CAP microspheres thought to be suitable
for suspension formulation and selected for further work.

The contribution of various factors like stirring speed, polymer solution concentration,
surfactant concentration, type of surfactant on micromeritic characteristics
of the microcapsules were examined.

 Table 1:

Microcapsules with different drug polymer (CAP) ratio (1:4, 1:3, 1:2) were
prepared and it was found that Drug polymer ratio does not affect percentage
yield and drug content (complies with the finding of Pongpaibul et. Al.), ¹¹
however, best quality microcapsules were obtained at 1:2 drug polymer ratios,
hence chosen for further study of suspension formulation (table2)

Table: 2

Microcapsules characterization and evaluation:

Drug content: The drug content of representative microsphere
samples was determined by Ultra – Violet spectrophotometer. (277 nm)

Particle Size Analysis: Particle size was determined microscopically
using Carl zeiss stereo zoom microscope (zeiss KL200)

Drug polymer compatibility: Drug, Polymer and microcapsules were
subjected FTIR (FT/IR5300 & DSC (DSC 821^e Metter Toledo)

In vitro release studies: in vitro dissolution studies was carried
by the changing pH method (Souder & Ellenbogen, 1958)¹² i.e.
first two hours in 0.1N HCL and next two hours in phosphate buffer pH 7.4, employing
dissolution test apparatus at 50 rpm & maintain temperature at 37^oC
using basket stirring element. The basket was covered with muslin cloth to avoid
leaching of microcapsules from the basket. Microcapsule equivalent to 75mg of
drug was employed & 5ml of sample was determined specrophotometricaly at
277nm.^H method (Sounder and Ellenbogen 1958) ¹² i.e. first
two hours in 0.1 N HCL & next two hours in phosphate buffer p^H
7.4 employing dissolution rate test apparatus XIX at 50 rpm & maintaining
temperature at 37c using basket stirring element.

Formulation and evaluation of suspension:

 Reconstitutable suspension of Tinidazole Microsphere was formulated
with suspending agent Carboxy methyl cellulose and Microcrystalline cellulose
along with flavor and buffering agent (sodium citrate and citric acid) and evaluated
for dry mixture includes sedimentation volume, ease of redispersion, viscosity
and pH.

Taste Masking Test:

A blind test was carried out with the formulation made up of 1:2 drug
polymer ratio microcapsules. Ten volunteers were participated in this study;
Non microencapsulated Tinidazole was included as reference control. Microcapsules
containing sucrose, flavor as the control formulation. Each volunteer was given
both formulations at one-hour interval.

They are asked to rate the taste and after taste of the formulation.

1.Tasteless,

2.Acceptable taste,

3.Slightly bitter,

4.Bitter,

5.very bitter,

They are also asked to rate the mouth feel as

1. No mouth feel,

2. Acceptable,

3. Slight mouth feel,

4. Mouth feel,

5. More mouth feel

Result & Discussion:

a) Effect of Stirring Speed on Tinidazole microcapsules

 Table 3:

The above result indicates that batches prepared at stirring speed 1200 rpm
& 1000 rpm have no significance effect on percentage yield & drug content.
However at higher speed microcapsules of smaller particle size are produced,
this is because at higher speed resistance towards the subdivision of dispersed
phase into smaller particle is reduced. This finding is in accordance with the
study carried by Huang & Sellassie¹³.

b) Effect of CAP Concentration on Acetone

The polymer concentration in acetone was varied by changing the volume of acetone used in the dispersed phase, while drug polymer ratio was kept constant.

Table 4:

The result (Table 4) indicates that percentage yield & drug content are
not significantly affected by polymer concentration. However in case of batch
7 & 8 relatively lower yield were obtained which may be due to incomplete
transfer of highly viscous solution i.e. disperse medium.

 c) Effect of Emulsifier

 I.: Effect Emulsifier concentrations

 Table 5

 The role of emulsifier in microsphere production by solvent evaporation
is the shot term stabilization of suspended polymer droplets, stabilization
to prevent aggregation & coalescence is only short term requirement, once
adequate solvent evaporation has taken place, to produce hardening of the polymer
droplet, coalescence & aggregation should not occur.

The results (Table5) indicate that the percentage yield & drug content are not significantly affected by the surfactant concentration. At a low concentration (0.1%). the emulsifier may not be sufficient to cover the droplet resulting in coalescence, however at high concentration (0.2%)w/v yielded free flowing spherical microcapsules.

II. Effect of Emulsifier types

Two emulsifier i.e. span 80 & span 85 were used in the emulsification of
the oil phase in liquid paraffin. The characteristics of microcapsules prepared
with 0.2% of each emulsifier are presented in table 6.     

Table 6:

The data in table 6 shows that the drug content & percentage yield are
not significantly affected by type of emulsifier but the morphology of microcapsules
was get affected, with span 85 sphericity of microspheres was improved as compared
to that with Span 80. Emulsifier reduces the surface free energy and hence tendency
to coalescence. It has been reported that the effect of reducing surface tension
by surface active agents increases as the hydrocarbon chain length increased
^14,15.Span 85 (Sorbiton trioleate) having number of hydrocarbon chains
than Span 80 (Sorbiton monoleate). Span 85 has1.8 HLB value whereas Span 80
has 4.3. Thus Span 85 a lipophilic surfactant is more effective as an o/o emulsifier
& hence in better stabilization of emulsion droplet, this result in spherical
free flowing microcapsules.

Compatibility Studies:

 1. IR interpretation: - IR data of pure Tinidazole indicated
the presence of band at1521 cm^-1 due to nitrogen. This band was similarly
observed for microcapsules with CAP suggesting that no chemical interaction
between CAP and Tinidazole took place.

2. Differential Scanning Colorimeter (DSC):- DSC of pure Tinidazole displayed
a melting endotherm at 126^oC.Microencapsulated Tinidazole also shows
endotherm at 121^oC  suggesting that the drug is compatible with
the polymer and no significant transmission of the drug have occurred after
processing. (Fig.1)

Dissolution studies:

Results of dissolution studies indicate that 50% of drug released in 0.1 N HCl due to higher solubility of drug in 0.1N HCL. Rest of the drug was released in phosphate buffer at PH 7.4 in less than two hours.

Stability study of Reconstitutable Suspension:

Suspension (Table 7, 8, 9) indicates that there is no significant change in sedimentation volume, redispersibility, viscosity and PH on storing the samples at room temperature and 37^oC even after seven days.

Table 7: Results of evaluation of Reconstituted Suspension.

Table 8: Results of Stability study of reconstituted suspension after
storing at room temperature for seven days.

Table 9: Result of evaluation of dry powder mixture by storing at 37^oC
for seven days.

Table10:

Taste panel evaluation of microencapsulated Tinidazole in liquid suspension
(Average Rating)

Table 10 indicates the result of typical tem person taste panel for evaluating
permanent suspension containing Tinidazole microcapsules and uncoated Tinidazole
suspension (The lowest numerical indicate the best product). These results clearly
indicate that the suspension containing the microcapsules is superior in taste
properties as compare to that of the raw material.

{mospagebreak title=Conclusion and References}

Conclusion:

The above data conclusively demonstrated that the micromeritics properties
(particle size, shape, drug content), micro encapsulation efficiency can be
significantly and suitably altered by the quantity and physicochemical characteristics
of the formulation excipients and variable selected. From the organoleptic evaluation
it was concluded that micro encapsulation is an effective method of taste masking
for Tinidazole.

Acknowledgement:

Authors thankful to Macleods Pharmaceuticals, Mumbai, Colorcon Asia Ltd for providing gift sample of Tinidazole and Polymers respectively.

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About Authors

Kshirsagar S. J.^1*, Pokharkar V. B.²

^*For Correspondence

Kshirsagar S. J

1. Senior Lecturer, STES Sinhgad Institute of Pharmaceutical Sciences,Kusgaon (Bk), Lonavala.sanjayjk@rediffmail.com

2. Professor,BVP’S Deemed University’s Poona College of Pharmacy & Research Centre,Kothrud, Pune