Formulation and Evaluation of Microemulsion containing

Anti-Hypertensive Drug

Supriya Shinde¹*, Vishal Yadav², Prakash Jadhav², Apoorva Jadhav²

¹Sawkar Pharmacy College, Jaitapur- 415004, Satara, Maharashtra, India.

²Department of Pharmaceutics, Arvind Gavali College of Pharmacy, Jaitapur- 415004,

Satara, Maharashtra, India.

*Corresponding Author E-mail: supi.pawar89@gmail.com

ABSTRACT:

The objective of this study was to develop an oral microemulsion formulation of the antihypertensive drug to enhance its bioavailability. The microemulsions were formulated by using Tween 20 as a surfactant, PEG 400 as co-surfactant and peppermint oil. Excipient ratio i.e. surfactant: co-surfactant ratio was kept 2:1, 3:1, 5:1. Microemulsions were characterized by particle size analysis and viscosity, after applying an experimental design. The formulation containing less surfactant: co-surfactant and less oil possessed less particle size and less viscosity. On the basis of appropriate parameters, formulation F7 was selected as an optimized batch optimized batch F7 was analyze for in vitro drug release study, zeta potential, physical stability. Batch F7 shows negative zeta potential which assures a good physical stability of the formulation. Dissolution study was carried out in 0.1 N HCl pH 1.2, and phosphate buffer pH 7.4% Drug release at 24 h for microemulsion formulation in the 0.1 N HCl pH 1.2, and phosphate buffer pH 7.4 was found to be 91.32% and 92.44% respectively, i.e. almost 90% release at all pH conditions within 24 h. So it was concluded that pure drug require maximum time for compete drug release than Microemulsion. Physical stability study of optimized batch F7 was carried out for 1 month. It was concluded that no change in formulation was observed after 1 month and observed for the change in Physical appearance, pH, average Particle size, and Zeta potential. It was observed that there was no change in the physical appearance Furthermore, there was no significant change observed.

KEYWORDS: Microemulsion, Telmisartan, Factorial design, Solubility, Dissolution, Stability.

INTRODUCTION:

The most ideal route of the drug administration is oral route due to better patient compliance and less production cost. The drug should present in the solution form for absorption through gastro-intestinal tract (GIT). For poorly soluble drugs, important factor is solubility and the dissolution.¹About 60-70% of pharmaceutical actives show poor systemic occurrence on oral ingestion due to poor dissolution through GI membrane (BCS class II, III, IV drugs).

Drugs which are poorly water-soluble involve several difficulties in various form dosage such as oral drug delivery, due to less bioavailability.

Preparation is orally administer solid dosage form for that drug whose absorption rate for poorly water-soluble. Therefore, the means determinants of oral bioavailability are dissolution and drug solubility. To improve absorption of liquid lipophilic and water-insoluble drugs and also the efficiency of absorption, in scientific literature various technique have been published.^1-3

· Particle size reduction via micronization

· Inclusion of active pharmaceutical ingredients into cyclodextrin

· Co-grinding

· Adsorption on porous structures

· Solid dispersion

· Microencapsulation

· Self-emulsification and self-micro emulsification

Composition¹:

The components of Microemulsion system:

· Oil phase

· Surfactant (Primary surfactant)

· Co-surfactant (Secondary surfactant)

· Co-Solvent

Application of microemulsion¹:

It is use as a system of drug delivery for its benefits, which include penetration ease and thermodynamic stability.

Advantages¹:

· It is very simple to manufacture and scale up as it forms spontaneously.

· This system raise rate of absorption and bioavaibility due to elimination of interfering variations.

· Solubility of lipophilic drugs can be improved.

· It is stable thermodynamically as compared to conventional system and hence for long term application that is suitable.

· Controlled and Sustained releases drug system is possible.

· It minimizes the first pass metabolism.

MATERIALS AND METHODS:

Materials:

Telmisartan was procured from Yarrow chemicals, Mumbai. Span 20, span 80, PEG 400, PEG 600, were purchased from Loba Chemicals Pvt. Ltd. Mumbai. Orange Oil was purchased from Sd-Fine chemicals limited, Mumbai; Tween 20, tween 80 was purchased from Loba Chemicals Pvt limited, Mumbai.

Methods:

Phase titration technique:

By using the unstructured emulsification method the Microemulsions are prepared (phase titration technique). Phase diagram construction of is a helpful approach to detect the complex series of relations that can be occur when various components are mixed. With the various association structures Microemulsions are formed along with (including emulsion, and oily dispersion etc). As a Quaternary phase diagram takes more time and difficult for interpretation, to find the various zones including zone of microemulsion the diagram is frequently constructed, in this every angle of figure shows 100 percent of the particular component. The section must be divided into w/o and o/w microemulsion by basically consider the components that is whether water rich and oil rich. Observations should be made carefully.

Evaluation parameter:

Visual inspection:

Visual inspection was made after every addition of water into surfactant and oil or mixture of surfactant and co-surfactant. The samples were recognized as microemulsion, as visual observation.

Measurement of pH:

With help out of a calibrated pH meter the pH values were calculated by placing the electrode directly into the dispersion.

Viscosity measurements:

The viscosity was found out without a dilution by using Brookfield Viscometer.

Zeta potential determination:

By using Zeta sizer Zeta potential of the samples was measured. The sample was put in zeta cells which are clear disposable and recorded results. Cuvettes were washing by methanol before filling the sample, prior to every experiment cuvettes should be rinsed by sample to be measured.

Particle size determination:

Particle size of drug contain Microemulsion was determined by analyzer, at 28°C. Each sample was analyzed three times.

Drug content estimation:

In volumetric flask Microemulsion contain 100mg drug was added in the 100ml 0.1N HCl. After filtration of solvent, take 1ml, in 50ml volumetric preparation and diluted, detected spectrometrically at 295nm. The drug content study was done in triplicate.

Application of experimental design:

By using 3²full factorial designs the experimental design was obtained as given in table 16 and table 17. The main plan is to prepare microemulsion of Telmisartan for dissolution enhancement and to measure the effects of formulation variables on response parameters. Concentration of Surfactant/Co-surfactant (X₁) and Oil (X₂) was chosen as variables Particle size (Y₁) and Viscosity (Y₂) as response parameters. A 3² full factorial design was selected as it is efficient and helps to study effect on response parameters with a minimum number of experimental run.

Independent variables:

1. Concentration of Surfactant/Co-surfactant (X₁)

2. Concentration of Oil (X₂)

Dependent/Response variables:

1. Particle size (Y₁)

2. Viscosity (Y2)

Table 1: Composition of different batches of Telmisartan Microemulsion preparation

Batches	Concentration of surfactant/ co-surfactant (X₁)	Concentration of oil (X₂)	Amount of Distilled water
F1	75(+)	25(+)	0
F2	75(+)	20(0)	5
F3	75(+)	15(-)	10
F4	70(0)	25(+)	5
F5	70(0)	20(0)	10
F6	70(0)	15(-)	15
F7	65(-)	25(+)	10
F8	65(-)	20(0)	15
F9	65(-)	15(-)	20

RESULTS AND DISCUSSION:

Preformulation studies of drug:

Organoleptic properties.:

The sample of the Telmisartan was odourless and white crystalline powder.

Melting point determination.:

The observed MP of Telmisartan was 265-266°C. This was in a standard range which is 264-267°C. This confirms that given drug sample was in a pure form.

Fourier transforms infra-red (FT-IR) spectroscopy of Telmisartan.:

Table 2 shows that functional group frequencies of Telmisartan. The reported frequencies which indicates the purity of Telmisartan.

Functional Group and Frequency (cm^-1):

NH stretch - 3518.16

OH band - 3053.32

C=C - 2474.67

C=O -1693.50

C=N -1602.85

COOH – 1450.47

CH Stretch- 1381.03

Differential Scanning Colourimetry (DSC):

The thermogram of Telmisartan is the endothermic peak at 264°C is indicative of its melting point. The MP of drug was in the standard range. This ensures purity of sample.

Telmisartan Solubility in various solvents:

Drug shows highest solubility in Methanol as compared to other solvents

Table 2: Telmisartan Solubility in various solvents

Solvent	Solubility (mg/ml)
Water	0.0032± 0.04 mg/ml
Methanol	0.816± 0.02mg/ml
0.1 N HCl of (pH 1.2)	0.521± 0.04 mg/ml
Phosphate buffer (pH 7.4)	0.317± 0.01 mg/ml

Ultra violet-visible spectrophotometric method for Telmisartan:

A. Study of spectra and detection of analytical wavelength:

Determination of λmax:

Telmisartan solution (10μg/ml) studied in UV spectrophotometer. After studying UV-spectrum of Telmisartan. In this spectrum Telmisartan shown maximum absorbance peak at 296nm so it was matches with the λmax which is reported in literature.

B. Calibration curve of Telmisartan in Methanol:

The absorbance and concentration linear relationship in 2-14μg/ml.

Drug excipient compatibility:

A. Sample analysis by Visual inspection:

There is no any interaction between drug and excipients by observising visual inspection.

B. Sample analysis by (FT-IR) Spectroscopy:

FT-IR spectra of mixture are shown in Figure 2. The spectra show no substantial shifting of the position of the functional groups. The peaks are only broadening, that indicating no major interaction observed between excipients and drug. If the liquid vehicle or excipients and the drug interact, the peaks subsequent to the functional group in the drug FT-IR will shift to dissimilar wave number to spectra of the pure excipients and pure drug.

Evaluation of microemulsion^{5, 12}:

Table 3: Particle size, Viscosity, Visual appearance and pH of different batches of Telmisartan Microemulsion

Batches	Conc. of Surfactant-Co-surfactant (%)	Conc. of oil (%)	Particle size (nm)	Viscosity (Cp)	Visual appearance	pH
F1	1	-1	173.2	139.2	Clear	6.1
F2	1	0	187.5	173.6	Clear	6.1
F3	1	1	219.2	191.2	Clear	6.2
F4	0	-1	143.1	90.8	Clear	6.2
F5	0	0	152.9	98.4	Clear	6.2
F6	0	1	170.3	111.2	Clear	6.3
F7	-1	-1	38.3	70.01	Clear	6.8
F8	-1	0	101.2	79.8	Clear	6.7
F9	-1	1	138.1	80.2	Clear	6.9

ANOVA of Particle size:

Polynomial equation for Particle size:

Y₁=+155.57+50.41X₁+28.87X₂-13.50X₁X₂-12.54X₁²-0.2100 X₂².................................................................... (1)

ANOVA of viscosity:

Polynomial equation for Viscosity:

Y₁=+102.47+45.66X₁+13.76X₂+10.45X₁X₂+22.20X₁²-3.50X₂²......................................................................... (2)

3-D response surface plots and polynomial equation no. 1 shows that concentration of Surfactant/co-surfactant and oil shows positive effect on the Particle size. It increases with increase in % Surfactant/co-surfactant and oil and decreases with decrease in % Surfactant/co-surfactant and oil. F7 Batch shows lowest particle size among all batches. Therefore, it can be derived that change in X₁and X₂variables.

Batch F7 contains lowest quantity of Surfactant/co-surfactant and oil due to which it shows less particle size i.e. 38.3 nm. Batch F3 contains highest quantity of Surfactant/co-surfactant and oil due to which it shows greater particle size i.e. 219.2 nm

The 3-D plot shows that particle size increased from. 38.3 nm to 219.2 nm

3-D response surface plots and polynomial equation no. 2 shows that concentration of Surfactant/co-surfactant and oil shows positive effect on Viscosity. It increases s with increase in concentration of Surfactant/co-surfactant and oil. As % of Surfactant/co-surfactant and % oil get increases, viscosity also gets increases. Therefore, it can be derived that the change in the X₁and X₂variables. Batch F7 contains lowest quantity of Surfactant/co-surfactant and oil due to which it shows less particle size and viscosity.

The 3-D plot shows that viscosity increased from 70.01 to 191.2%.

Evaluation of optimized batch^2-3:

Particle size analysis:

Size analysis of particles of the optimized batch was done. The particles size of the optimized batch was 38.3 nm as given in Figure 4.

Figure 4: Particle size analysis of optimized batch

Diffrential Scanning Colourimetry:

DSC thermogram of Telmisartan showed a characteristic endothermic peak which is corresponding to is melting point. DSC of pure Telmisartan shows characteristic, endothermic peak at 264^oC, which is connected with its melting point (Tm). The Microemulsion system shows lower value of delta H than drug indicating lower energy needed for Solubalization, i.e. drug was molecularly discrete within the Microemulsion and no probable interface between excipient and drug occurred. Such a loss of the peak of drug upon formulation of the Microemulsion system occurred due to entire expression of all drug thermal features. In addition, found that the total loss of the drug melting peak indicates the drug amorphization had taken place.

Zeta potential analysis:

To determine the surface charge and potential stability of Microemulsion, Zeta potential is an important surface characterization technique. Usually large negative or large positive zeta potential value essential for Microemulsion stability as electrostatic revulsion between particles with avoids aggregation of same charge particles. Batch F7 shows zeta potential negative, which assures stability of preparation. The zeta potential of telmisartan Microemulsion was measured. Zeta potential value of batch F7was originate -39.1mV. Optimized batch shows -ve charge on its surface.

In vitro release study of drug^{4,
6, 7}:

Figure 5: Dissolution profile of plain drug and Microemulsion Batch F7 in 0.1 N of HCl pH 1.2 and PBS pH 7.4

In-vitro dissolution was carry for pure drug and Microemulsion formulation Batch F7 to study % cumulative drug release in different pH conditions. In-vitro dissolution study was approved out for pure drug in two different buffers. Dissolution study was performing in 0.1 N of HCl of pH 1.2 and PBS pH 7.4. % Drug release at 24 h in 0.1 N of HCl pH 1.2 and PBS pH 7.4 was 65.1 and 51.7 respectively. It was accomplished that drug release in these pH conditions was pH dependent. Telmisartan shows less solubility in alkaline pH, so that % drug release is found to be less than acidic pH. For Microemulsion formulation dissolution reading was done in a 0.1 N HCl pH 1.2 and PBS pH 7.4. % Drug release at 24 h for Microemulsion formulation in the 0.1 N HCl pH 1.2 and PBS pH 7.4 was 91.32 % and 92.44 % respectively, i.e. almost 90% release at all pH conditions within 24 h. So it should accomplished that pure drug require maximum time for compete drug release than Microemulsion.

Table 4: % Cumulative drug release of pure drug in different buffers

Time (h)	%CDR of Plain drug in 0.1 N of HCl (pH 1.2)	%CDR of Plain drug in Phosphate buffer (pH 7.4)	%CDR of Batch F7 0.1 N of HCl (pH 1.2)	%CDR of Batch F7 Phosphate buffer (pH 7.4)
0	0.8	0.8	2	2.02
1	11.6	8.3	20.7	21.1
2	15.3	11.2	29.4	31.3
3	21.9	20.1	32.1	39.7
4	39.1	26.2	41.9	47.2
5	46.6	30.1	50.6	58.4
6	51.9	34.4	59.7	65.5
7	59.2	32.3	68.5	71.2
8	63.3	40.9	76.3	79.1
12	59.2	45.2	83.1	86.4
24	65.1	51.7	91.3	92.4

Physical stability study of batch F7:

For 1 month Physical stability study of the batch F7 was done. It was accomplished to here was no alteration in formulation was find out later than 1 month, all results are accessible in Table 5

Table 5: Physical stability study of batch F7 observations initial and after 1 month

Parameters		Initial observation	Final observation (after 1 month)
Physical appearance		Clear	Clear
pH		6.8	6.7
Particle size		38.3 nm	38 nm
Zeta potential		Negative	Negative
% Drug release	pH 1.2	91.3%	90.0%
% Drug release	pH 7.4	92.4%	92.2%

CONCLUSION:

For the BCS class II drugs, the dissolution process is the rate-limiting step, which can be determines the rate and the degree of its absorption. Drugs having water solubility problem will be released at a slow rate, this causes limited dissolution rate within the gastrointestinal tract contents. For drugs having problem with water solubility one challenge is to enhance the rate of dissolution. The main aim was preparation and evaluation of Microemulsion containing anti-hypertensive drug for dissolution enhancement using factorial design. In this study the preformulation study was performed for confirmation of drug. Based on the melting point study and FT-IR the drug was established to be authentic. The microemulsions were formulated by using tween- 20 as a surfactant, PEG 400 as co-surfactant and peppermint oil. Excipient ratio i.e. surfactant, co-surfactant ratio was kept 2:1, 3:1, 5:1. Drug–excipient compatibility was checked and confirmed by FT-IR study. The Microemulsions were formulated by the unprompted emulsification method. Microemulsions were characterized by particle size analysis and viscosity. The formulation containing less surfactant: co-surfactant and less oil possessed less particle size and less viscosity. Experimental design was applied for the further studies the optimized batch formulation F7 was selected. Further optimized batch F7 was analyze for drug release study in- vitro, zeta potential, physical stability. Batch F7 shows zeta potential negative that is a good stability of formulation. In DSC study Microemulsion system shows lower value of delta H than drug indicating lower energy needed for solubilization. Physical stability reading of the batch F7 was accepted for 1 month. It was accomplished so as to here no alteration in formulation was find later than 1 month and observed for the change in Physical appearance, pH, average Particle size, and Zeta potential. It was observed in the physical form here no alteration furthermore; there was any considerable change in Physical appearance, pH, average Particle size, and the Zeta potential of Microemulsion preparation after the storage for 1 month. These results show high stability and suitability of Microemulsion. From all the above observations it can be concluded that, Microemulsion preparations could be a promising approach to improve drug release and drug efficacy of Telmisartan. These studies suggest a better drug delivery through the microemulsion with an added advantage of improved drug release, drug efficacy, stability and reduce toxicity.

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Received on 18.01.2020 Modified on 16.03.2020

Research J. Pharm. and Tech. 2020; 13(12):5726-5732.

DOI: 10.5958/0974-360X.2020.00997.X