Formulation and Evaluation of Tinidazole Microgel for Skin Delivery

 

Pooja Yadav, Sunil Shah, Chandra Kishore Tyagi

Sri Satya Sai University of Technology and Medical Sciences, Sehore-466001, Madhya Pradesh, India.

*Corresponding Author E-mail: om11agra85@gmail.com

 

ABSTRACT:

The objective of the present study was to formulate and optimize tinidazolemicrogel. To achieve these objective fourteen formulations of microgel were prepared by emulsion solvent evaporation method using Eudragit polymer. A 32 factorial design was employed in formulating the microgel with concentration of surfactant (A) and stirring speed (B) as independent variables. Percent drug release was considered as dependent variable. The effect of drug-polymer concentration, surfactant concentration, cross-linking agent and stirring speed were evaluated with respect to entrapment efSficiency, particle size, surface characteristics, micromeritic properties, DSC study and in vitro drug release studies. The particle size and entrapment efficiency were found to be varied by changing various formulation parameters like surfactant concentration and stirring speed etc. IR study confirmed the drug-polymer compatibility and scanning electron microscopy indicates that the microgel have the rough and porous surface due to arising as a trace of solvent evaporation during the process. The release profile of tinidazole from Eudragitmicrogel was pH dependent. In acidic medium, the release rate was much slower; however, the drug was released quickly at pH 7.4. It is concluded from the present investigation that Eudragitmicrogel are promising as a carrier for targeted delivery of tinidazole.

 

KEYWORDS: Microgel, Skin Delivery, Tinidazole, Permeation Constant, Fungal Diease.

 

 

 

INTRODUCTION:

The fundamentals of successful formulation are to deliver the active substance at target organ with minimal discomfort and side effects. In this respect, transdermal route excels because of avoidance of hepatic first pass metabolism, typical peak trough plasma profile, ease of administration etc.1,2 However the improvement of drug permeability through the skin is always a difficult problem, because of barrier function of human skin epithelia to exogenous substances. Therefore, the major challenge in topical administration is to increase the drug penetration into the skin. Moreover, most of the pharmaceutical substances are lipophilic in nature.

 

The clinical efficacy of such drugs is being impeded by their low aqueous solubility resulting in poor absorption and penetration mainly when they are designed for transdermal administration. One way is to use the skin penetration enhancers3,4 and the other way is to develop appropriate vehicles to increase the solubility and the thermodynamic activity of the drug and then to increase the permeation5,6,7.

 

Currently, there is considerable interest in colloidal drug delivery systems (liposomes, nanoparticles, microspheres, macromolecular drug complexes) for the purpose of drug targeting, controlled release and protection of drug substance. Liposomes in particular have been extensively investigated as a potential carrier for polar and nonpolar drugs but only with limited success since they are relatively unstable, tend to be leaky and have low drug carrying capacities. Microgels on the other hand, have advantages over both the colloidal systems under investigations and the conventional emulsions, suspensions and micellar solutions because of their excellent stability, good potential of dissolving a large amount of drug substance in their hydrophobic domain and may be used as alternative drug carriers. In recent years microgels have attracted a great deal of attention because of their considerable potential to increase the transdermal delivery of a wide range of drug molecules8,9. Previous reports have confirmed that the incorporation of a lipophilic drug into the internal phase of an o/w microgel has become an attractive technique for the percutaneous administration of the drug due to high solubilizing capacity10.

 

This approach favours high concentration gradient across the diffusion membrane, leading to an increase in the activity of the drug in the vehicle and thereby improving the drug diffusion rate. The disperse phase acts as a reservoir which maintains a constant concentration gradient over the skin for a long period11.

 

The present study aims at formulating microgel gel of Tinidazole for topical application, since Tinidazole a synthetic triazole antifungal drug used for the treatment of superficial and systemic fungal infections. The microgel has the capacity to penetrate deep in to the skin so transdermal permeation is suspected.

 

Transdermal route demands that the formulation should release the drug which must penetrate the stratum corneum and reach the systemic circulation in therapeutic concentrations to show its effect12. An optimized formulation will efficiently release the drug and because of its composition, may also facilitate drug transport across the skin. For the drugs which are poorly water soluble, a vehicle is needed which can increase its solubility and thus the concentration gradient (which is a very important factor governing the permeation of the drug through the skin). Previous studies have confirmed that the incorporation of a lipophilic, poorly water soluble drug in the internal phase of an oil-in-water microgel has become an attractive technique for transdermal administration of drug due to its enhanced solublizing capacity, resulting in higher flux through the skin. Microgels offer several advantages over the conventional transdermal drug delivery sources such as higher penetration efficacy, higher solublizing power, transparency, excellent stability leading to longer shelf life and ease of manufacturing13.

 

Tinidazole undergoes extensive first pass metabolism after oral administration. Therefore the transdermal route would be beneficial to improve its bioavailability by circumventing first pass metabolism.

 

Since Tinidazole is poorly water soluble, a vehicle is needed which can increase its solubility and thus increase the concentration gradient which is a very important factor governing the permeation if the drug through the skin. Previous studies have confirmed that the incorporation of a lipophilic drug in the internal phase of an oil-in-water microgel has become an attractive technique for transdermal administration of drug due to its enhance solubilising capacity, which also results in enhanced bioavailabilty of the drugs.

 

Therefore it was proposed to develop topical microgel gel based system of Tinidazole a poorly water soluble antifungal drug, with the aim of increasing its solubility and thus its transdermal flux in order to provide effect of drug locally and in skin cells and it should provide action through systemic circulation also after absorption in to the blood stream.

 

MATERIALS AND METHODS:

Tween 80: CDH, Mumbai. Tinidazole: Torrent Pharmaceuticals, India, Carbitol: Gattefosse, France, Oleic acid: CDH, Mumbai, Isopropyl Myristate: CDH, Mumbai, Olive oil: CDH, Mumbai, Olive oil: CDH, Mumbai, Jojoba oil: Shinyo chemicals Co., Japan, Triacetin: Shinyo chemicals Co., Japan, Sodium hydroxide: MERCK, Mumbai, Potassium dihydrogen orthophosphate: S.D. fine chemicals, Mumbai.

 

Physical Characterization of Tinidazole

Physical characteristics:

The drug (API) was characterized on the basis of monograph14.

 

Identification Tests:

FTIR spectral analysis:

The FTIR spectral analysis was carried out using KBr pellet technique.

 

U.V. analysis:

10 mg of Tinidazole was dissolved in methanol and make up the volume to 100 ml with methanol. 5 ml of the above solution is diluted with methanol to 100ml. then it was examined between 200 nm to 400 nm. The solution showed maximum absorbance at 263 nm which was same as the reported one15.

 

Analytical Methodology:

Preparation of working solution

Various working solutions were prepared freshly when needed according to USP 2000.

 

Phosphate buffer (pH 7.4):

50 ml of 0.2 M potassium dihydrogen orthophosphate was mixed with 39.5 ml of 0.2M sodium hydroxide and volume was made up to 200 ml with distilled water.

Preparation of 0.2M potassium dihydrogen orthophosphate solution

27.22 g of potassium dihydrogen orthophosphate was dissolved in small quantity of distilled water in a 1000 ml volumetric flask and volume made up to 1000 ml with distilled water.

 

Preparation of 0.2M sodium hydroxide solution:

8 g of sodium hydroxide was dissolved in distilled waterin a volumetric flask and volume made up to 1000 ml with distilled water.

 

Preparation of medium of study:

Phosphate buffer (pH 7.4) and polyethylene glycol (PEG) as cosolvent in a ratio of 60:40 were mixed (based on the solubility profile of the drug) to obtain the medium in which release studies were to be carried out.

 

Intrinsic stability testing of drug solution:

For testing the intrinsic stability of the drug in the release medium, a known concentration of drug solution in the release medium was prepared and was divided in three parts. Each part was kept at different temperatures viz. refrigeration (8o C), room temperature (25o C) and 37o C. UV spectra was taken initially and after 48h again and observed for any change in λmax or any significant change in absorbance in orderto ascertain the intrinsic stability of the solution.

 

Preparation of calibration curves:

For release studies

10mg of the drug was dissolved in 100 ml of mixture of phosphate buffer (pH 7.4) and 40% PEG (100µg/ml) and different dilutions ranging from 1-10µg/ml were prepared after appropriate dilution with the mobile phase. Samples were filtered using 0.45µm filter and analyzed using HPLC.

 

Preformulation Studies:

Solubility studies

The solubility of Tinidazole was determined in water and phosphate buffer (pH 7.4)+ PEG 400, since this buffer was used as release media in permeation studies. An excess amount of drug was taken in three flasks each containing water and phosphate buffer (pH 7.4). Samples were kept on a water bath maintained at 37 ± 0.5o C for 48h and were then centrifuged at 10,000 rpm for 10 min. The aliquots of supernatant were filtered through a 0.45μm membrane filter. After appropriate dilutions with methanol, solubility of Tinidazole was determined using HPLC at 263 nm.

 

Determination of partition coefficient of drug:

The partition coefficient of the drug was determined in octanol/buffer. 50 mg of drug was accurately weighed and added to a mixture containing 20 ml each of octanol and buffer. The flask was than shaken for37 ± 0.5o C for 24h. The mixture was then transferred to a separating funnel and allowed to equilibrate for 10h. The aqueous and octanol phases were separated and filtered through membrane filter.

 

Drug excipients interaction studies:

UV, assay of drug in formulation, and DSC were carried out to ascertain any interaction between the drug and the excipients.

 

Formulation of Microgels:

Construction of pseudo ternary phase diagrams:

On the basis of solubility studies, combination of olive oil and oleic acid (1:1) was selected as the oil phase. Tween 80 and Carbitol were chosen as surfactant and cosurfactant respectively. Distilled water was used as an aqueous phase. For the determination of existence zone of microgel, pseudoternary phase diagrams were constructed using water titration method. Surfactant and cosurfactant (Smix) were mixed in different weight ratios (1:0, 0.5:1, 1:1, 2:1 and 3:1). These Smixwere chosen in increasing concentration of surfactant with respect to cosurfactant for detailed study of the phase diagrams.

 

For each phase diagram, oil and specific Smix were mixed well in different ratios. Sixteen different combinations of oil and Smix (1:9, 1:8, 1:7, 1:6, 1:5 1:4, 1:3.5, 1:3, 3:7, 1:2, 4:6, 5:5, 6:4, 7:3, 8:2 and 9:1) were made so that maximum ratio could be covered for the study to delineate the boundaries of the phases formed precisely in the phase diagrams. Slow titration with aqueous phase was done for each weight ratio of oil and Smix and visual observation was used for transparent and easily flowablemicrogel. The physical state of microgel was marked on a pseudo three component phase diagram with one axis representing the aqueous phase, one representing oil and the third representing a mixture of surfactant and co-surfactant at fixed weight ratio.

 

RESULTS AND DISCUSSION:

Physical Characterization of Tinidazole

Physical characteristics:

 

Physical Appearance

White Granular powder.

Odour

Odourless

Melting point

Melting point was determined by capillary method

Using melting point apparatus it was found to be 1680C

Reported value: 167 – 1700C

Solubility

Insoluble in water (<3µg/ml)

Freely soluble in Methylene chloride

Sparingly soluble in Tetrahydrofuran

Very slightly soluble in alcohol

Loss on drying:

At 100-105°C for 4 hours loss on drying was found to be 0.24%

Weight of drug before drying =1.000gm

Weight of drug after drying =0.9976gm

Weight loss =0. 0024gm

% Weight loss = 0.0024 x 100

= 0.24%.

 

Fig 1: DSC Scan of Tinidazole sample

 

Identification Tests:

FTIR spectral analysis:

The FTIR spectral analysis was carried out using KBr pellet technique (Fig. 2 & 3)

 

U.V. analysis:

10 mg of Tinidazole was dissolved in methanol and make up the volume to 100 ml with methanol. 5 ml of the above solution is diluted with methanol to 100ml. then it was examined between 200 nm to 400 nm. The solution showed maximum absorbance at 263 nm (Fig. 4) which was same as the reported one.

 

 

Fig. 2: FTIR scan of Tinidazole reference.

 

 

Figure 3: FTIR scan of Tinidazole sample.

 

Figure 4: UV Scan of Tinidazole test and reference in methanol

 

Analytical Methodology

HPLC analysis of Tinidazole

Column: C8 (5µm particle size, 10cm)

Mobile phase: water: Acetonitrile: Diethyl amine (40:60: 0.05%v/v)

Flow rate: 1.5 ml/min

Detection: 263 nm

Run time: 15 min

Retention time: 9.283 min

 

 

Fig. 5: HPLC curve of Tinidazole in mobile phase (Retention time 9.283 min).

 

Table 1: Area values of Tinidazole in mobile phase at 263 nm using HPLC.

Sr. No

Concentration

(μg/ml) (X)

Area

(Y)

(n=3)

Area value

by

regression

± SD

1

1

37456

35424

2032

2

2

75340

70848

4492

3

3

113412

106272

7140

4

4

146508

141696

4812

5

5

184510

177120

7390

6

6

222736

212544

10192

7

7

258192

247968

10224

8

8

302648

283392

19256

9

9

334104

318816

15288

10

10

378038

354240

23797

11

20

712120

708480

3640

12

30

1023450

1062720

39270

13

40

1445600

1416960

28640

14

50

1788160

1771200

16960

 

Fig. 6: Calibration curve of Tinidazole in mobile phase at 263 nm using HPLC.

y=35424x.

Coefficient of correlation (R2) = 0.999.

Slope (m) = 35424.

 

 

Fig. 7: HPLC curve of Tinidazole in methanol (Retention time 9.8 min).

 

Table 2: Area values of Tinidazole in methanol at 263 nm using HPLC.

S. No.

Concentration

( μg/ml) (X)

Area

(Y)

Area value by regression

± SD

1

1

39102

38424

678

2

2

78168

76848

1320

3

3

118306

115272

3034

4

4

158408

153696

4712

5

5

198510

192120

6390

6

6

236612

230544

6068

7

7

276714

268968

7746

8

8

316816

307392

9424

9

10

396020

384240

11780

10

20

736581

768480

31899

11

30

1135468

1152720

17252

12

40

1524560

1536960

12400

13

50

1945600

1921200

24400

 

 

Fig. 8: Calibration curve of Tinidazole in methanol at 263nm using HPLC.

y= 38424x.

Coefficient of correlation (R2) = 0.9994.Slope (m) = 38424

 

Preformulation Studies:

Solubility studies

The mean solubility of Tinidazolein phosphate buffer (pH 7.4) and water was found to be 2.85 μg/ml and 2.7 μg/ml respectively.

 

Determination of partition coefficient of drug:

Partition coefficient was calculated to be 5.049.

 

Table. 3:Apparent partition coefficient of Tinidazole in octanol/buffer

Total amount of

drug (µg)

Amount in

 organic phase(µg)

Amount

In aqueous

phase(µg)

Partition

Coefficient

50000

49985.3

2.447

5.049

 

Drug excipients interaction studies:

UV, assay of drug in formulation, and DSC were carried out to ascertain any interaction between the drug and the excipients.

 

FORMULATION OF MICROGELS:

Construction of pseudo ternary phase diagrams

On the basis of solubility studies, combination of olive oil and oleic acid (1:1) was selected as the oil phase. Tween 80 and Carbitol were chosen as surfactant and cosurfactant respectively. Distilled water was used as an aqueous phase. For the determination ofexistence zone of microgel, pseudoternary phase diagrams were constructed using water titration method. Surfactant and cosurfactant (Smix) were mixed in different weight ratios (1:0, 0.5:1, 1:1, 2:1 and 3:1). These Smixwere chosen in increasing concentration of surfactant with respect to cosurfactant for detailed study of the phase diagrams.

 

For each phase diagram, oil and specific Smix were mixed well in different ratios. Sixteen different combinations of oil and Smix (1:9, 1:8, 1:7, 1:6, 1:5 1:4, 1:3.5, 1:3, 3:7, 1:2, 4:6, 5:5, 6:4, 7:3, 8:2 and 9:1) were made so that maximum ratio could be covered for the study to delineate the boundaries of the phases formed precisely in the phase diagrams. Slow titration with aqueous phase was done for each weight ratio of oil and Smix and visual observation was used for transparent and easily flowable microgel. The physical state of microgel was marked on a pseudo three component phase diagram with one axis representing the aqueous phase, one representing oil and the third representing a mixture of surfactant and cosurfactant at fixed weight ratio.

 

Table 4: Microgel points for the mixture containing S/ CoS ratio 1:0.

Oil Phase: Oleic acid: olive oil (1:1)

Surfactant: Tween 80

Cosurfactant: Nil

S. No.

% Oil

(v/v)

% Smix

(v/v)

Ratio

(oil: S mix)

% Water

(v/v)

1.

36.36

54.55

1:1.5

9.09

2.

48

32

1:0.6

20

3.

63.64

27.27

1:0.42

9.09

4.

28.17

56.34

1:2

15.49

5.

30.30

60.61

1:2

9.09

6.

24

56

1:2.3

20

7.

25

58.33

1:2.3

16.67

8.

27.27

63.64

1:2.3

9.09

9.

21.28

63.83

1:3

14.89

10.

22

66.67

1:3

11.11

11.

18.87

66.04

1:3.5

15.09

12.

20

70

1:3.5

10

13.

18.18

72.73

1:4

9.09

14.

14.08

70.42

1:5

15.49

15.

14.93

74.63

1:5

10.45

16.

10

60

1:6

30

17.

12.12

72.73

1:6

15.15

18.

12.82

76.92

1:6

10.26

19.

10.53

73.68

1:7

15.79

20.

11.24

78.65

1:7

10.11

21.

8.89

71.11

1:8

20

22.

9.43

75.47

1:8

15.09

23.

10

80

1:8

10.00

24.

0.48

4.29

1:9

95.24

 

Table 5: Composition of microgels.

 

Microgel

Oleic acid: olive oil

(%v/v)

Tween 80+

 carbitol

(%v/v)

Distilled

 water

 (%v/v)

Tinidazole

(mg)

2%w/v

B1

2

18

80

20

B2

4

36

60

20

B3

6

45

49

20

B4

8

50

42

20

B5

10

55

35

20

B6

15

60

25

20

 

DISCUSSION:

Once the appropriate microgel components have been selected, pseudoternary phase diagrams should be constructed to define the extent and nature of microgel region and surrounding two & three phase domains. The construction of pseudoternary phase diagrams was started using surfactant i.e. tween 80 alone (1:0). It was found that the region of microgel existence was very less and most of the region was composed of emulsions. Now along with surfactant, cosurfactantcarbitol was also incorporated in the ratio 1:1 and pseudoternary phase diagram was constructed. It was found that region of microgel existence increased greatly.

 

Increasing the concentration of surfactant (2:1), resulted in even larger area of microgel existence, along resulted in the reduction of the microgel existence area and more and more of area was composed of gels. The influence of concentration of cosurfactant on the microgel existence was also seen by constructing phase diagram in the ratio of 1:2. It was seen that the region of microgel formation was narrow.

 

The existence with emulsion, gels or microgel gels area. Increasing surfactant concentration further from 2:1 to 3:1of microgel region whether large or small depends on the capability of that particular surfactant or surfactant mixture to solubilize the oil phase. The extent of solubilization results in a greater area with more of clear, homogenous solution. It was seen that when the surfactant (tween 80) was used alone, oil phase was solubilized to a lesser extent implying that surfactant alone was not able to reduce the interfacial tension of the oil droplets to sufficiently low level & thus was not able to reduce the free energy of the system to ultra-low level desired to produce microgels. When a cosurfactant was added, the interfacial tension was reduced to much low level and very small free energy was achieved which helped in larger microgel area existence in phase diagram. With a further increase in surfactant from 1:1 to 2:1, a further drop in interfacial tension and free energy was achieved resulting in maximum area of microgel formation. With a further increase in surfactant concentration (3:1), the interfacial tension of interfacial film increased as compared to above and more of gel area and less of microgel area was observed. An increase of cosurfactant (1:2) resulted in a narrow region due to the same reason.

 

Thus, pseudoternary phase diagrams 1:1, 2:1 & 3:1 were selected for the formulation of microgels. For the selection of formulations from the phase diagrams full extent of oil region showing microgel was selected with the minimum surfactant showing the presence of microgel at that particular oil composition.

 

The thermodynamic stability testing was done to ascertain that the prepared microgels were stable when subjected to freeze thaw cycle (to check stability at low temperature) and centrifugation studies (to check stability at high shear). All the formulations subjected to above studies came back to their original form when subjected to freeze thaw and did not show turbidity or phase separation on high speed centrifugation. The above formulations were then loaded with the drug. The drug loaded microgels were again tested for thermodynamic stability to show that there was no effect of drug loading on the stability of microgels.

 

All the drug loaded formulations donot shows any phase separation, turbidity, change in colour or drug precipitation and thus, were found to be stable.

 

The content of oil and surfactant mixture in microgel affected the skin permeation rate of Tinidazole significantly. The reason for low permeability of drug from microgels with 2%,4% & 6% oil phase probably could be because of the lower amount of possible permeation enhancing components viz. oil and surfactant mixture. As the oil phase reached an optimum concentration i.e 8% the permeation increased significantly with formulations in all the phase diagrams. As the composition of oil phase and surfactant increased further i.e 10, 15%, there was a further reduction in the drug permeation, which could be because of the fact that at higher content of oil and surfactant mixture the affinity of the Tinidazole to the microgel increased while its affinity to the stratum corneum decreased. Thus it was found that after 8 % oil and 50% surfactant mixture the drug permeation continued to decrease .Hence microgel B4 was selected as the optimized formulation and was then formulated in to gel.

 

To compare the skin permeation of Tinidazole with microgel, in vitro skin permeation from control formulation was done. The permeation study was also carried out using the drug loaded neat component viz. neat surfactant (Tween 80 &Carbitol mixture) and drug saturated oil phase. It was seen that compared to control there was more than 8 times increase in flux from microgelgel. Almost same results were obtained from neat surfactant. The oil phase however, showed 524 times reduced flux compared to microgel gel.

 

If the components in the microgel are acting as permeation enhancer, an increase in surfactant concentration should increase the permeation of the drug through the skin. Keeping this thing in mind, surfactant was increased from optimized surfactant concentration i.e 50 % in formulation B4 It was found that as the concentration of surfactant was increased skin permeation of Tinidazole decreased. This could be due to an increased thermodynamic activity of the drug in microgels at lower concentration of surfactant and cosurfactant, as Tinidazole is poorly water soluble but soluble in surfactant mixture.

The optimized microgel B4 was characterized for different parameters like solubility, particle size, viscosity, particle shape etc. It was found that the drug showed a solubility of 24.6 mg/ml in the microgel which is about 9100 fold higher than the solubility of drug in water (2.75µg/ml) which leads to greater concentration gradient towards skin leading to greater flux across the skin.

 

The mean particle size of 97.4% of the disperse phase was found out to be 172.9nm with a polydispersity of 0.130. The formulation had a suitable pH of 6.95 and a refractive index of 1.463. TEM images showed the shape of dispersed phase to be spherical.

 

The prepared microgel gel was homogeneous and did not show any skin irritancy. From this it can be concluded that the prepared microgel gel was safe to be used as topical drug delivery system.

 

The control and the microgels were subjected to in vitro skin permeation studies using Keshary-Chein cell with rat skin. From the study it was found that formulation B4 exhibited satisfactory results as the cumulative amount of drug permeated from other formulations was lesser than B4. On this basis B4 was considered better formulation and then it was formulated in to gel. The data of the skin permeation studies of the microgel gel was further evaluated in order to ascertain permeation kinetics. From the permeation studies the rate constant for zero and first order rate kinetics were calculated for each time interval and their coefficient of variation (Cv) & standard deviation (SD) were calculated. It was seen in the case of microgel gel that less Cv was observed for zero order kinetics and more of Cv was observed for first order kinetics. Therefore, it was found that permeation from microgel gel followed zero order permeation kinetics. In order to ascertain that whether the zero order kinetics achieved in the case of microgel gel above was because of the formulation or due to the nature of the skin, in vitro permeation data of control was also evaluated for permeation kinetics. The studies conducted on control revealed that less Cv was observed for first order rate kinetics while more Cv was found for zero order kinetics. This shows that the permeation of drug from the control through the skin followed first order kinetics. Thus it was concluded that the permeation of the drug from microgel gel through the skin follows zero order kinetics.

 

To further substantiate the mechanism by which microgel gel increase the permeability of the drug through the skin, thermodynamic studies were performed. The Arrhenius plot between logKp values vs 1/T was found to be linear in the temperature range selected. The Eact values of Tinidazole was calculated from the slope of Arrhenius plot (Eact/2.303R) and were found to be 2.5454 K cal/mole and 4.4219 Kcal/mole respectively for the microgel gel and control. This showed that there had been a significant decrease of 73% in Eact when the drug was incorporated in the gel. This showed that microgel gel have the ability to lower the interfacial energy between the skin and the vehicle upon its intimate contact with skin lipids and water, further enhancing skin delivery.

 

All the microgel gel stored at different temperatures showed no change in consistency. Stability studies according to ICH guidelines at 40 ºC and 75 % RH predicted a degradation of 2.10% of Tinidazole at the end of 90 days. According to Arrhenius plot method, degradation rate constant at 25ºC was found to be 1.8262×10-4 day-1 predicting a shelf life of 1.58 years.

 

The purpose of interaction studies was to determine any interference and interaction of the drug with other ingredients of the formulation i.e. oil and surfactant mixture. However, in the interaction studies the drug was shown to be fairly stable and inert to the excipients used in the microgel.

 

The UV spectrum revealed that the formulation & the pure drug solution exhibited the same absorption maxima (λmax).

 

The assay results were found satisfactory with the percentage recovery ranging from 99.93 % to 99.99 % (mean 99.96) indicating that the drug was undecomposed and stable in the formulation.

 

The DSC thermogram of the drug excipients mixture was found to be the same as that of pure drug.

 

From the results of mentioned studies, it can be inferred that the drug remained intact and no chemical interaction seemed to occur between the drug and excipients therein.

 

From Inhibition zone values of the test with the two controls, it was observed that the microgel gel had the highest zone of inhibition both at 100ppm and 200pm. It may be therefore concluded that incorporation of the drug in microgel gel exhibit better antimycotic activity against Candida albicans in comparison with marketed formulation and control. The zone of inhibition of microgel gel was found to be 25 and 27.66 mm respectively for 100 and 200ppm concentration.

 

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12.      Claudia, V., Katharina, S. 2004. Influence of carrageenan on the rheology and skin permeation of microemulsion formulation. J. Control. Rel. 95, 257-265.

13.      Jessy, S., Srinivas, M.R. 2004. Microemulsion as drug delivery systems. Pharma Times. 36, 17-23.

14.      Physician’s desk reference Edition – 56, 3275 – 3279 (2002).

15.      Clark’s analysis of drugs and poison, (2005)

 

 

 

Received on 10.01.2021            Modified on 31.01.2021           

Accepted on 17.02.2021              ©A&V Publications all right reserved

Research J. Topical and Cosmetic Sci. 2021; 12(1):43-50.

DOI: 10.52711/2321-5844.2021.00007