Advancement, Optimization and Evaluation of Captopril Buccal Film

Marwa Farea Mohammed Masoud, Dr. B. Prakash Rao, Ahmed Mohammed Abdalla

Department of Pharmaceutical Technology, Faculty of Pharmacy,

#33/2, Thirumenahalli, Hegde Nagar Main Road, Bangalore – 560064, Karnataka, India

E-mail: marwahmasood9@gmail.com

ABSTRACT

Captopril is an ACE inhibitor, antagonizes the effect of the Renin Angiotensin Aldosterone System. The RAAS is a homeostatic mechanism for regulating hemodynamics, water and electrolyte balance. Captopril is well absorbed after oral administration, but is subject to first-pass metabolism in the liver resulting in only about 60-75% absolute bioavailability. Buccal route offers several advantages such as rapid absorption and higher blood levels due to high vascularization of the region and prolonged duration of action. Hence, in the present work buccal films of captopril were prepared with the objective of avoiding first pass metabolism and prolonging the duration of action. The mucoadhesive polymer used in the formulations are HPMC K4M in various concentration. The buccal films were prepared by the solvent casting method. The formulations were evaluated for various physicochemical parameters, in-vitro release studies, swelling study, stability study. The product with HPMC K4M was considered as the best product with respect to percentage drug release and retention in the buccal cavity. They were also more comfortable due to absence of erosion and less viscosity of surrounding environment. The best mucoadhesive performance was exhibited by the optimized formulation F9 -Drug (50mg) follows the zero order. This product was further subjected to stability studies, the results of which indicated no significant changes with respect to folding endurance, moisture content, moisture uptake, ex vivo mucoadhesive strength and drug content during the period of two months.

Key word: Buccal Film; Captopril; HPMC K4M; Solvent Casting; Optimization.

1. INTRODUCTION:

The normal blood pressure is usually 120/80mmHg, hypertension is a condition where the systolic blood pressure is more than 120mmHg while the diastolic blood pressure is greater than 80mmHg. However hypertension is associated with cardiovascular disease (CVD) risk factors, incidence, and mortality. According to hydraulic equation, Blood pressure (BP) is directly proportional to product of blood flow(CO) and the resistance to passage of blood via Peripheral Vascular Resistance(PVR)1-2.

BP=(CO ) X (PVR)

Captopril being an antihypertensive medicament with plasma half-life of 2-3 hour and only 40 % of the drug gets into the systemic circulation as a result of hepatic first pass metabolism. Captopril inhibits the conversion of angiotensin I to angiotensin II by inhibition of ACE. The hindrance has been proved in both healthy human subjects and in animals by showing that the elevated blood pressure caused by exogenously administered angiotensin I was managed by captopril3.

Buccal mucosa is the most appropriate for local, as well as systemic delivery of drugs. The unique physiological features make the buccal mucosa as a perfect route for mucoadhesive drug delivery system. These favorable circumstances include bypass of hepatic first-pass effect and overcoming pre systemic elimination. The utilization of the oral cavity membranes as sites of drug administration has been increasing interests for the past years. The absorption of therapeutic compounds from the oral mucosa provides a direct

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entry of the drug into the systemic circulation, hence overcoming the first-pass hepatic metabolism along with gastrointestinal drug degradation, both of which are associated with peroral administration4. Mucoadhesive polymers received considerable attention as platforms for buccal delivery of drugs due to their ability to localize the dosage form in the specific regions to enhance drug bioavailability5.

2. METHODOLOGY:

2.1 Material:

Captopril, HPMC K4M, Ethanol, Glycerin and Tween 80 were purchased from Yarrow chemicals Pvt Ltd – India.

2.2 Methods:

2.2.1. Differential scanning calorimetry (DSC)6

Differential scanning calorimetry studies was conducted to study the changes in amorphous to crystalline or vice-versa or any polymorphic changes during formulation of the buccal film. Thermograms of drug, mixture of drug and polymer physical mixtures in ratio 1:1. The sample were placed in aluminum pan and heated in the rate of 70ºC ⁄min, to a temperature of 120°C using a differential scanning calorimeter. Results are shown in figures.2.2.2. Fourier Transfer Infrared spectrophotometer (FTIR)7

The FTIR studies were done for the drug, the polymers and the drug-polymer physical mixture of the drug in 1: 1 ratio were mixed and the corresponding disks were prepared by applying 5.5 metric tons of pressure in a hydraulic press using FTIR Spectrophotometer. The disks were examined over a wave range (4000-400 cm).

2.2.3. Preparation of standard graph8:

Estimation of Captropril8: Standard Graph of CaptoprilDetermination of λmax

λmax was determined by scanning 10µg/ml solution of Captopril against 1N sodium hydroxide (NaOH) solution as a reagent blank in spectrum mode between 200-400nm.Preparation of stock solution Primary stock solution of Captopril in 1N sodium hydroxide (1000µg/ml) was prepared by dissolving 25mg Captopril in 25ml 1N sodium hydroxide. Then 1ml of the above mixture was diluted to 10ml using 1N sodium hydroxide to get 100µg/ml which is referred to as the stock solution.Preparation of calibration curve in 1N sodium hydroxide.From the stock solution containing 100µg/ml Captopril is transferred to 10ml volumetric flask and then diluted to 10ml using 1N sodium hydroxide. The absorbance of all the prepared solutions of 2,4,6,8,10,12,14, &16µg/ml was then measured at 265nm using UV Spectrophotometer (Model UV 1700 Shimadzu). The reading was recorded in triplicate and a graph of concentration verses absorbance was plotted.Design expert:By using Stat-Ease software, by implying the central composite design we took two variables that is the Polymer concentration and the Speed while taking 4 responses which included weight variation, film thickness, swelling index, % moisture content and 8hr release The levels are given in table1.

Table -1: Variables taken along with the Levels.

Variable factors Level -1.14 -1 0 1 1.14

HPMC K4M 158 200 300 400 441

2

Glycerin 0.017 0.1 0.3 0.5 0.58

3. Formulation and Evaluation

3.1. Preparation of buccal film by solvent casting method9

Nine formulations (F1-F9) were prepared as in table-2 by solvent casting method using different concentration of HPMC K4M and Glycerin in different quantities and each film with surface area of approximately 4cm2 was loaded with the drug. The drug is dissolved in ethanol and stirred till dissolved then labeled as solution A , while the polymer is dissolved in water containing Tween 80 along with Glycerin until the polymer dissolved then the solution is labeled B. Transfer solution B to solution A and stir well then keep aside to free the air bubbles, then pour the solution into the ring that was earlier place on mercury surface. Leave it overnight to dry, the dried film is the covered in aluminum foil and stored in a desiccator until further use.

Table-2: Formulation Chart of Captopril

INGREDIENT(% w/w)

FORMULATION CODEF1 F2 F3 F4 F5 F6 F7 F8 F9

Drug (mg) 50 50 50 50 50 50 50 50 50

HPMC K4M (mg) 200 400

200 400 158 441

300 300 300

Glycerin (ml) 0.1 0.1 0.5 0.5 0.3 0.3 0.017 0.582

0.3

Tween (ml) 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1Solvent (ml) 2 2 2 2 2 2 2 2 2

4. Evaluation:

4.1. Physical appearance10

Visual analysis of formulated film formulation can provide results of desired organoleptic properties like color, flavor and taste. Recently, e-tongue software are useful to determine taste of formulation. Uniformity in color and odor along with good taste brings patient acceptability. The general appearance and elegance of film was identified visually, which include shape, color, presence of an odor, taste, surface texture etc.

4.2. Weight variation11

Weight variation of the prepared films was studied by individually weighing 10 randomly selected patches. Such determination was performed for each formulation.

4.3. Film Thickness10

The thickness of 3 patches (2x2 cm) of each formulation was measured using Digital thickness measurement apparatus and the results were analyzed for mean and standard deviation. Three films from each batch were used, and an average value was calculated. Film was selected random from individual formulation and thickness was measured.4.4. Folding Endurance11

Folding endurance of the film was determined repeatedly folding the film at the same place until it break. The number of times the film could be folded at the same place without breaking was the folding endurance value.

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4.5. Drug Content in the Film12

To determine the drug content uniformity, three film units of each formulation were taken in separate 100 ml volumetric flasks, 100 ml of pH 6.6 phosphate buffer was added and continuously stirred for 24 h. The solutions were filtered, diluted suitably and analyzed at 265 nm in a UV spectrophotometer (Model UV 1700 Shimadzu). The average of drug contents of three films was taken as final reading.

4.6. Percentage of Moisture Uptake13

The patches were weighed accurately and placed in a desiccators where a humidity condition of 80-90% RH was maintained by using saturated solution of potassium chloride. The patches were kept until uniform weight is obtained, then taken out and weighed. The percentage of moisture uptake was calculated as the difference between final and initial weight with respect to initial weight.

4.7. Surface pH study12

To determine surface pH of films, buccal films were left to swell for 1 h on the surface of the agar plate, prepared by dissolving 2% (w/v) agar in warmed isotonic phosphate buffer of pH 6.6 under stirring and then poured the solution into the Petri dish allowed to stand till gelling at room temperature. The surface pH was measured by means of pH paper placed on the surface of the swollen film.

4.8. In-Vitro Drug Diffusion Studies14

In-vitro, drug release studies were carried out by attaching buccal mucosa to one end of the Franz diffusion cell which acted as donor compartment. The buccal films containing drug was placed inside donor compartment which is agitated continuously using a magnetic stirrer and then temperature was maintained at 37±1°C. The receptor compartment consisted of 100 ml of phosphate buffer (pH 6.8). 2 ml sample was withdrawn at periodic intervals from the receptor compartment and replaced with fresh phosphate buffer (pH 6.8) immediately. The drug release was analyzed spectrophotometrically at 265 nm. The results are shown in Table 6.

4.9. Stability studies15

Best formulation was stored in screw capped small glass bottles at room temperature and in stability chamber at 40 ± 1°C and 75% RH. Samples were analyzed for physical appearance, residual drug content, and in vitro release after a period of 30, and 60 days. Initial drug content was taken as 100% for each formulation. The results are shown in Table 8.

5. RESULTS AND DISCUSSION

5.1. DSC of Captopril

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Fig 1: DSC of Captopril

DSC of Captopril + HPMC K4M

Fig 2: DSC of Captopril + HPMC K4M

5.2. Fourier Transfer Infrared Spectrophotometer (FTIR)

Fig 3. FTIR spectrum of Pure Captopril

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Fig 4. FTIR spectrum of Captopril +HPMC

TABLE 3. Fourier Transfer Infrared spectrophotometer (FTIR)

BOND Wave no cm-1 of pure drug Drug + HPMC K4MS-H, Strech 2500 2500C=O,Strech.Sp2 1747.51 1747.51N-H, Strech 1593.74 1593.74O-H, Bending 1334.74 1334.74

5.3 Standard graph of fluconazole

TABLE 4. Standard graph of Captopril

0 2 4 6 8 10 12 14 16 180

0.05

0.1

0.15

0.2

0.25

0.3

f(x) = 0.015171568627451 xR² = 0.999936218870947

standard graph

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Concentration Absorbance 0 0.002 0.0314 0.066 0.0928 0.12210 0.15412 0.18114 0.21316 0.241

Fig 5: standard curve of captopril

5.4. Physical appearance

The general appearance and elegance (shape, color, presence of an odor, taste, and surface texture) found satisfactory in each formulation. The films were homogenous, clear and flexible (Figure 6). The additions of enhancers to the prepared films increased their flexibility and enhanced their moisture uptake. Glycerin in F-6 played its plasticizer role and gave a film better transparency.

Fig 6. Buccal patch

5.5. Weight variation The weight of the buccal films ranged from 101-111mg. Polymer concentration had a direct impact on the weight of the film. An increase in the polymer increased the weight of the buccal film. The results of the weight of the buccal film for all the nine formulation is given in Table 5.5.6. Film thickness Film thickness should be controlled within a range of 0.19 ± 0.01 mm and 0.37 ± 0.02 mm ± 5% variation of standard value.3 All the drug-loaded films have uniform thickness throughout. The optimized F-5 film was found to have thickness of 0.27±0.04mm. The results for all the formulations is given in Table 5.5.7. Folding Endurance Folding endurance was measured and readings are given the Table 5. The highest folding endurance was observed in the case of F8 (268) and the lowest in the case of F5 (260). The range of folding endurance study ensured flexibility of these formulated buccal patches.5.8. Drug Content.The drug content (%) in all formulations varied between the range 90.4±0.56% and 97.6±0.36%. This indicates that the drug dispersed uniformly throughout the polymeric film. Results are shown in Table 5. 5.9. Percentage of moisture uptake. The moisture uptake (%) study of various films was done at high relative humidity like 80% and 90% for a period of 3 days. In all cases, the moisture uptake was found to increase with increase in relative humidity. The low moisture uptake by all these formulations was observed at various levels of relative humidity. This low moisture uptake (%) by Captopril buccal patches can help to retard any hydrolytic degradation, and patches will remain stable. The results for the nine formulation is shown in Table5.5.10. Surface pHThe surface pH of all the films was between pH 6.25 to 6.94. Results for all the formulation is given in Table5.

Table 5: Evaluation parameters Evaluation Parameters FORMULATION CODE

F1 F2 F3 F4 F5 F6 F7 F8 F9Weight variation (mg) 102 106 103 108 101 111 104 106 105Film Thickness (mm) 0.21 0.33 0.23 0.35 0.19 0.37 0.27 0.31 0.29Folding Endurance 262 265 264 268 260 268 265 265 266Drug content % 91.5 95.7 92.4 96.2 90.4 97.6 93.2 94.8 94.1% Moisture uptake 4.34 4.86 4.52 5.21 3.86 5.28 4.68 4.78 4.73Surface pH 6.54 6.74 6.59 6.78 6.25 6.8 6.64 6.85 6.74

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5.11. In-vitro Drug Release

Table.6: Kinetics of Drug release zero order for F1-F9

Time FORMULATION CODEF1 F2 F3 F4 F5 F6 F7 F8 F9

0 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.001 21.93 18.76 17.64 28.001 27.16 11.48 18.20 17.64 17.822 33.69 29.30 20.25 44.43 30.98 26.97 25.48 24.36 24.363 36.96 44.15 33.51 48.07 37.15 40.23 37.05 37.24 37.244 43.96 55.16 41.91 55.44 42.47 58.43 41.91 43.79 44.245 51.15 64.13 49.008 61.70 47.04 67.49 55.16 54.79 54.796 57.59 68.70 56.29 66.93 65.15 74.12 63.38 62.63 62.637 73.09 74.59 72.16 73.19 70.76 81.03 73.28 71.78 71.788 87.82 88.52 89.12 85.12 89.32 90.51 88.72 87.82 85.32

Fig.7: Comparison of Zero order kinetics of in-vitro drug release F1-F5

0 1 2 3 4 5 6 7 80

102030405060708090

100

F1F2F3F4F5

Time(hr)

%Dr

ug d

iffus

ed

Fig.8: Comparison of zero order kinetics of in vitro drug release F6-F9

0 1 2 3 4 5 6 7 80

102030405060708090

100

F6F7F8F9

Time(hr)

%Dr

ug D

iffus

ed

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Table 7: Drug release kinetic data for 9 different formulations

Regression value (r2)

FormulationF1 F2 F3 F4 F5 F6 F7 F8 F9

Zero order 0.991 0.978 0.990 0.991 0.993 0.995 0.989 0.996 0.999First order 0.929 0.969 0.938 0.969 0.916 0.913 0.969 0.891 0.992Higuchi 0.955 0.944 0.943 0.955 0.964 0.939 0.881 0.940 0.944Korsmeyer-Peppas

0.995 0.973 0.995 0.985 0.993 0.996 0.994 0.993 0.995

n value 1.16 1.18 1.16 1.24 1.22 1.28 1.43 1.39 1.33

5.9. Stability study:

Stability studies were carried out on most satisfactory formulation as per ICH Guidelines Q1C. The most satisfactory formulation was sealed in aluminum foil and stored in stability chamber. These were stored 400C for 2 months. Results showed that there were no significant changes found in physicochemical parameters and in vitro diffusion of optimized formulations (F3) after stability study.

Table 8: Stability data for elevated temperature (40±2°C and relative humidity 75± 5%)

Evaluation Parameter

0 month 1 month 2 month

Weight variation

108 107 107

Film Thickness

0.26 0.26 0.26

Folding Endurance

266 264 264

Drug content %

96.2 95.4 92.2

% Moisture uptake

3.86 3.80 3.76

Where,* All values are mean ± SD, n =3.

6. CONCLUSION

Captopril buccal film was formulated and it indicated that the buccal film is a better option compared to the oral dosage form hence minimizing the disadvantage related to the oral dosage form. The polymer HPMC K4M was utilized and it can be novel approach to deliver the release of the drug. Various drugs can be formulated as buccal films. The buccal film can be formulated best for the drugs that undergo first pass metabolism. From the results and discussion, it was concluded that the buccal film with polymer was in acceptable range showing the acceptable results of physical appearance, Weight variation, Film thickness, Folding Endurance, Drug Content, Percentage of moisture uptake, Surface pH and in-vitro Drug Release was found to be stable after 2months. From the in-vitro release studies, F6 showed maximum drug release of 90.51% in 8hours. An increase in polymer decreases the drug release from the formulation. However

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amongst the formulations F6 showed better results indicating that captopril buccal film can be used to deliver drugs that undergo first pass metabolism with the aim of better efficacy.

7. ACKNOWLEDGEMENT

Our sincere thanks to Karnataka college of pharmacy for the support and the facilities provided for the project.

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