Formulation and Evaluation of Fast Dissolving Buccal Patches of Tenofovir Disoproxil Fumarate

 

D. Maheswara Reddy*, C. Madhusudhana Chetty, Y. Dastagiri Reddy, P. Komali, B. Sri Divya, S. Sandhya Rani

Santhiram College of Pharmacy, Nandyal 518501, AP, India.

 

ABSTRACT:

Background and objectives: Tenofovir disoproxil fumarate is a anti-retroviral agent. It is used in the treatment of HIV-1 infection in adults and pediatric patients of 2 years of age and older. It is also indicated for the treatment of chronic hepatitis-B in adults and pediatric patients 12 years of age and older. The present work is designed to prepare and evaluate mucoadhesive buccal film of Tenofovir disoproxil fumarate as a novel form of fast releasing dosage form. The objective of this study was to develop oral drug delivery system in the form of fast dissolving film which overcomes first pass metabolism and the drug achieve to specific site, for greater therapeutic action. Methods: Buccal films of Tenofovir disoproxil fumarate were prepared by solvent casting method. The prepared films were evaluated for the various evaluation parameters like thickness, surface pH, weight uniformity, content uniformity, folding endurance, swelling index, in vitro drug release study. Results: All the formulations exhibited good results for physicochemical characterizations. In in vitro drug release study, the films exhibited fast release within 5 hours. The formulation F1 (containing HPMC3cps and croscarmellose) showed no irritant effect on buccal mucosa. It was revealed that Superdisintegrants composition had significant influence on drug release. Thus, conclusion can be made that stable dosage form can be developed for Tenofovir disoproxil fumarate for fast release by buccal patches.

 

 

 

INTRODUCTION:

Oral route has been the commonly adopted and most convenient route for drug delivery. Oral route of administration has been received more attention in the pharmaceutical field because of the more flexibility in the designing of dosage form than drug delivery design for other routes, ease of administration as well as traditional belief that by oral administration the drug is well absorbed as the food stuffs that are ingested daily.¹

 

The mucosa of the mouth is very different from the rest of the gastro intestinal tract and morphologically is more similar to skin.

 

Although the permeability of skin is widely regarded as poor, it is not generally appreciated that the oral mucosa lacks the good permeability demonstrated by the intestine.²

 

Tenofovir disoproxil fumarate, marketed by Gilead Sciences, belongs to a class of anti-retroviral drugs known as nucleoside analogue reverse transcriptase inhibitors (NRTI’s), an enzyme crucial to viral production in HIV infected people. Tenofovir is indicated in combination with other anti-retroviral agents for the treatment of HIV-1 infection in adults and pediatric patients of 2 years of age and older. It is also indicated for the treatment of chronic hepatitis-B in adults and pediatric patients 12 years of age and older.^3,4,5

 

MATERIALS:

Tenofovir disoproxil fumarate was obtained as gift sample from the Hetero drugs, Hyderabad. HPMC3cps, Superdisintegrants were obtained from Otto reagents, SSG, Citric acid and Sodium lauryl sulfate were obtained from SD fine chemicals, Mumbai. All other reagents and solvent used were of analytical grade.

 

Method of preparation of patches:⁶

The mucoadhesive buccal patches were formulated using solvent casting technique.

The fast dissolving buccal patch was prepared by dissolving the film forming polymers (HPMC3cps) in the water followed by addition of glycerol as plasticizer to the resulted polymer solution. The above solution was allowed to stir on the magnetic stirrer for 4 h to homogenize the solution. Then the solution kept in the vacuum desiccators to remove the air bubbles. Meanwhile, in the separate beaker the solution of all ingredients with TDF is prepared and allowed standing for 45 minutes. Finally, both the solutions were mixed and homogenized on the magnetic stirrer for another 1 h. Then the solution was casted into the Petriplates for drying into the oven at 50^oC for 24 h. After drying the film was cut into suitable size and stored in aluminum foil in well closed container.

 

Table 1: Composition of buccal patches of Tenofovir disoproxil fumarate

 

Calibration curve of Tenofovir Disoproxil Fumarate:⁶

A. Preparation of 6.8 p^H phosphate buffer:

Dissolve 28.8g of disodium hydrogen phosphate and 11.45g of potassium dihydrogen phosphate in 1000ml of distilled water to produce 6.8 p^H phosphate buffer.

 

B. Calibration curve TDF:

100mg of pure drug was taken in a 500ml standard flask and to this add 6.8 p^H phosphate buffer and shake vigorously. From this stock solution with draw 1ml of solution and dilute to 100ml with phosphate buffer. Finally, different concentrations like 10µg/ml, 20µg/ml, 30µg/ml, 40µgml, and 50µg/ml were prepared. These are further diluted and samples were subjected to spectrophotometric analysis (UV-Visible) to determine absorbance at ƛ_max of 260nm. From the curve obtained, a line equation and regression analysis were determined.

 

Evaluation tests for patches:⁷

1.     Weight Variation:

The patches were cut in the required sizes and weights were calculated individually.

 

2.     Thickness:

The thickness of each patches was measured using thickness tester (screw gauge) at different positions of the film and the average was calculated.

 

3.     Moisture Absorption:

The buccal patches were weighed (w1) and placed in desiccators having anhydrous Aluminium chloride. After 3 days, the patches were reweighed (w2). The % moisture absorption was calculated using

 

                                              Final weight-Initial weight

% Moisture absorption = –––––––––––––––––––––––––– X 100

                                                            Initial weight

 

4.     Moisture Loss:

The buccal patches were weighed (w1) and placed in desiccators having anhydrous. Calcium chloride. After 3 days, the patches were reweighed (w2). The % moisture absorption was calculated using

 

                     Initial weight - Final weight

% Moisture loss =  ––––––––––––––––––––––––––––––– X 100

                                                 Initial weight

 

5.     Folding Endurance:

Folding endurance of the buccal patches was determined by taking 20mm diameter of patch was repeatedly folding at the same place till it broke. The no of times of patch could be folded at the same place without breaking gave the value of the folding endurance.

 

6.     Drug content uniformity:

The films were tested for the content uniformity. A film of size 1 cm² was cut and placed in the beaker containing 100 ml of 6.8 p^H phosphate buffer. The films were allowed to dissolve in the solution. The contents were transferred to a volumetric flask. The absorbance of the solution was subjected to spectrophotometric analysis (UV-Visible) to determine absorbance at ƛ_max of 260nm.

 

7.     Surface p^H:

For surface p^H determination, the patches were left to swell for 2 hours in 6.8 p^H phosphate buffer. The surface p^H was measured by means of p^H paper placed on the surface of the patches. The mean of three readings was recorded.

 

8.     Swelling Index:

A drug loaded film of 1 cm² was weighed and then placed in the 50 ml of 6.8 p^H phosphate buffer. After 2 hours the patch was removed and again reweighed. The difference in the final and initial weights gave the results of weight increase due to the absorption of water and swelling of film.

 

                                       Final weight - Initial weight

Swelling index = –––––––––––––––––––––––––––––––––– X 100

                                               Initial weight

 

9.     Disintegration time:

10. It is an important tool in designing the dosage form. It is the time required for the dosage form to break up into granules of specified size under carefully specified conditions.

 

11. Diffusion Studies:

The prepared patches were cut according the required size and the attached to the open-end glass test tube; it is placed in the beaker containing 6.8 p^H phosphate buffer. The beaker is kept on the magnetic stirrer and temperature of 37±0.5⁰ C was maintained. Aliquot amount of samples are withdrawn at an interval of 1 minute and same amount of fresh medium was replaced. The absorbance of the solution was subjected to spectrophotometric analysis (UV-Visible) to determine absorbance at ƛ_max of 260 nm.

 

12. Kinetic study:

The matrix systems were reported to follow the zero order release rate and the    Diffusion mechanism for the release of the drug. To analyze the mechanism for the release and release rate kinetics of the dosage form, the data obtained was fitted into, Zero order, First order, Higuchi matrix and peppa’s model. In this by comparing the r Values obtained, the best fit model was selected.

 

a.     Zero order kinetics:

Drug dissolution from pharmaceutical dosage forms that do not disaggregate and release the drug slowly, assuming that the area does not change and no equilibrium conditions are obtained can be represented by the following equation

 

Qt = Q₀+K₀t

 

Where Qt is the amount of drug dissolved in time t, Q₀ is the initial amount of drug in the solution and Ko is the zero order release constant.

 

b.    First order kinetics:

To study the first order release kinetics the release rate data were fitted to the following equation.

log Qt = log Q₀+ k1t/2.303.

 

Where Qt is the amount of the drug released in time t, Qo is the initial amount of the drug in the solution and K1 is the first order release constant.   

 

c.     Higuchi model:

Higuchi developed several theoretical models to study the release of water Soluble and low soluble drugs incorporated in semisolids and or solid matrices. Mathematical expressions were obtained for drug particles dispersed in a uniform matrix behaving as the diffusion media. And the equation is

 

Qt = KH.t_1/2

 

Where Qt is the amount of drug released in time t, KH is the Higuchi Dissolution constant.

 

d.    Korsmeyer and Peppa’s model:

To study this model the release rate data are fitted to the following equation.

 

Mt/M =K.tn

 

Where Mt/M is the fraction of drug release, K is the release constant, t is the release time and n is the Diffusion exponent for the drug release that is dependent on the shape of the matrix dosage form.

 

RESULTS AND DISCUSSION:

1. Preformulation studies:

1. Preparation of Standard curve of Tenofovir disoproxil fumarate:

The absorbance of the solution was measured between 200 – 400 nm, using UV spectrophotometer with distilled water as blank. The values are shown in table no. 5. A graph of absorbance Vs Concentration was plotted which indicated in compliance to Beer’s law in the concentration range.

 

 

Fig No.1. Standard graph of TDF

 

Identification of pure drug:

FTIR Spectroscopy:

The FTIR spectrum of pure drug of Tenofovir Disoproxil Fumarate shows the following functional groups at their frequencies. The IR spectra of Tenofovir Disoproxil Fumarate shown in spectrum no.1

 

Solubility:

Tenofovir Disoproxil Fumarate is soluble in methanol, ethanol. Slightly soluble in DMSO.

 

Melting point: 

It has melting point of 113-115⁰C.

 

 

Fig No. 2.: FT-IR Spectrum of pure drug (Tenofovir Disoproxil Fumarate)

 

 

Fig No. 3.: FT-IR Spectrum of TDF+HPMC K4M

 

Evaluation Results of Prepared TDF Buccal Patches:

1.     Weight variation:

Weight variation test was performed. The weights of the patches were between 0.30 gm to 0.35 gm. Hence all patches formulations passed weight variation test. Results are shown in table no.2.

 

 

2.     Thickness:

Thickness of all the formulations was between 0.21 mm to 0.28 mm. Results are shown in Table No.2.

 

3.     % Moisture absorption:

% Moisture absorption of all formulations was between 6.45 % to 14.70 %. Results are shown in Table No. 2.

 

4.     % Moisture loss:

% Moisture loss of all the formulations was between 9.09 % to 16.12 %. Results are shown in Table No.2.

 

5.     Folding endurance:

The number of times the strip could be folded at the same place without breaking gives the exact value of folding endurance (a measure of fragility). The folding endurance was measured manually for the prepared films. A strip of 2×2cm was cut evenly and repeatedly folded at the same place till it broke.

 

6.     Drug content:

Percentage drug content of all formulations was between 55.34 to 86.53%. The results are shown in Table no.2.

 

7.     Surface pH:

The surface pH of prepared inserts was found be in range of 6.2 to 7. This indicated that the prepared inserts would not alter the pH of the tear fluid in the eye. Results are shown in Table no.2

 

8.     Swelling index:

Swelling index of all the formulations was between 0.52% to 0.86%. Results are shown in Table No.2.

 

9.     Disintegration time:

Disintegration time of all the formulations was between 32 to 59. Results are shown in Table No.2.

 

10. In vitro release studies:

The in vitro drug release studies were performed by using a modified US Pharmacopoeia paddle-type dissolution apparatus (using 900ml of PBS 7.4 as dissolution medium). The dissolution studies are crucial because one needs to maintain the drug concentration on the surface of the Stratum corneum consistently and keep it substantially higher than the drug concentration in the body, to achieve a constant rate of drug permeation. A circular film with an internal diameter of 1 cm was used for the study and a stainless-steel ring was employed to hold the patch at bottom. All dissolution studies were performed at 32±0.5◦C, at 50rpm. Samples were withdrawn at different time intervals and analysed spectrophotometrically. % drug released were plotted against time for different formulations.⁷

 

Table No. 2: Evaluation studies of formulated buccal patches

 

Table No. 3. Cumulative % drug release of various formulation

 

Table No. 4. Higuchi model: √T v/s % CDR

 

 

Fig No. 4. Cumulative Percentage drug release of Formulation – 1

 

 

Fig No. 5. Higuchi model of Formulation – 1

 

CONCLUSION:

These results indicated that F1 (drug 300 mg) with croscarmellose of tenofovir buccal patches has achieved the objective of considerable influence on the physio chemical characteristics and releasing property. The concentration of Croscarmellose in the formulation determines the drug release from the patches. As the concentration of Croscarmellose increases, drug release also increases. So, finally the best concentration of Croscarmellose was found to be 24 mg and formulation 1 gave the best results.

 

ACKNOWLEDGMENT:

The authors are thankful to Secretary Dr. M. Santhiramudu through Dr. C. Madhusudhana Chetty Principal of Santhiram college of Pharmacy, Nandyal, Andhra Pradesh, for providing necessary facilities to carry out this research work.

 

REFERENCES:

1.      Donald L. Wise, Hand Book of Pharmaceutical Controlled Release Technology, PP.no. 431-433.

2.      Vyas and Khar, Control and Novel Drug Delivery, PP.no. 351-58.

3.      https://www.drugbank.ca/drugs/DB00300.

4.      https://www.drugbank.ca/salts/DBSALT000172

5.      Dennis J. Cada, Terri L. Levien, Danial E. Baker. Tenofovir Disoproxil Fumarate Tablets. Formulary Drug Reviews. 2009; 44(2): 165-178.

6.      Kaur M., Rana A. C., Seth N., Fast dissolving films an innovative drug delivery system. International Journal of Pharmaceutical Research and Allied Sciences. 2013; 2(1):14-24.

7.      Dakshata A Patel, Prof. Sandip A Tadavi, Dr. Bhushan R Rane, Dr. Sunil Pawar. Formulation and Evaluation of fast mouth dissolving film of tenofovir disoproxil fumarate. Internal Journal of Advanced Research in Science Management and Technology. 2016; 2(7):1-8.

8.      Ceballos A, Cirri, M, Maestrelli, F, Corti G & Mura P, influence of formulation & process variables on in-vitro release of theophylline from directly compressed Eudragit matrix tablets IL, Farmaco. 2005; 60: 913-18.

 

 

 

Received on 17.11.2019           Modified on 10.03.2020

Accepted on 04.05.2020         © RJPT All right reserved