INTRODUCTION:

In the recent times, the research efforts have been engrossed on the development of site-specific drug delivery systems to improveoral bioavailability and reduce dose-dependent side effects of drugs. Buccal drug delivery is a means to provide a substitutefor various other conventional modes of systemic drug administration, as buccal mucosa is quite permeable with an increased blood supply. Hence, buccal mucosafunctions as an excellent site for drug absorption^1,2. Interfacial molecular attractive forces between surfaces of biological substrate and natural/synthetic polymersplay a significant role in the adhesion of polymerwith biological target for a prolonged time period³. Oral transmucosal delivery of drugs avoids first pass effect as well ascircumventspre-systemic elimination in gastrointestinal tract. Such considerations make the oral mucosa especiallyfeasible and desirable site for the delivery of drugs into systemic circulation.

Hypertension indicates a condition of prolonged and persistent rise in blood pressure higher than the normal range.Losartan potassium is a type of angiotensin receptor blocker commonly known by the brand name Cozaar which is used to treat hypertension. Dizziness is a common side effect of losartan. It usually affects persons who are just beginning treatment, as their bodies are adjusting to drug⁴. The drug has 33% oral bioavailability and readily absorbed from gastrointestinal tract with 98.6 to 98.8% protein binding. Losartan potassium undergoes metabolism in liver and gut wall. Approximately, 5% of the total oral dose was metabolized. It is un-metabolized by the liver. Elimination half-life is 2 h⁵. Effective dose of losartan potassium is approximately 35mg. As losartan potassium belongs to BCS Class III drugs, that have high aqueous solubility as well as low permeability, there is anecessity to enhance permeability of drug. On account of physicochemical characteristics and pharmacokinetics of losartan potassium, it was identifiedthat the drug has a requirement to be fabricated into buccal patch formulations and the drug was found to be appropriate for it.

The current research was primarily focused on the development and evaluation of patient friendly oral mucoadhesive buccal patches of losartan potassium. Several batches of losartan potassium buccal patches were developed by solvent casting method utilizing different polymers in various proportions to enhance permeability, bioavailability and therapeutic efficacy of model drug–losartan potassium. The reason for selection of mucoadhesive buccal patches as the formulation approach was the ability of such drug delivery system to retain the formulation in contact with mucosal surface resulting in better absorption as well as prolonged residence time.

MATERIALS AND METHODS:

Losartan potassium was received as a gift sample from Hetero Drugs Limited, Hyderabad, India. Propylene glycol was purchased from Antares Chem Private Limited, East Mumbai. HPMCK4M, HPMC K15M, HPMC K100M and Eudragit L100 were procured from Loba Chemie Private Limited and Hetero Drugs Ltd., Hyderabad, respectively. All other chemicals used were of analytical grade.

Pre-Formulation Studies:

Pre-formulation studies on losartan potassium comprised observation of colour and odour; determination of solubility, melting point determination as well as drug-excipient compatibility testing.

Solubilitystudy:

Pre-formulation solubility testing was done by the selection of suitable solvent systems in order to solubilise losartan potassium and various additives.

Melting point determination:

Purity of losartan potassium was evaluated by melting point determination. Presence of trace amount of impurity can be revealed by lowering and widening in melting point range.

Drug - excipients compatibility studies:

Fourier transformation infrared (FT-IR) analysis :

An FT-IR spectrophotometer (Alpha Bruker) was employed for infrared analysis of the prepared samples. About 4 to 5 mg of losartan potassium was mixed with dry KBr and the sample was analysed at transmission mode over the range of 4000-400 cm^-1wave number⁶.

Formulation Development:

Calibration of standard curve of losartan potassium:

100 mg of losartan potassium was accurately weighed and dissolved in 100 ml of phosphate buffer solution, pH 6.8 in 100 ml volumetric flasks. The resultant solution was considered as stock solution which had 1 mg/ml concentration (1000 µg/ml). Further, 100 µg/ml solution was prepared by dilution of 10 ml of stock solution with phosphate buffer solution, pH 6.8 up to 100 ml. Required aliquots of 1 ml, 2 ml, 3 ml, 4 ml, 5 ml were diluted up to 10 ml with buffer solution to obtain concentrations in terms of 10 µg/ml, 20 µg/ml, 30 µg/ml, 40 µg/ml and 50 µg/ml, respectively. Absorbance of each solution was analysed with the help of UV-visible spectrophotometer at the λ_max of 235 nm using phosphate buffer solution, pH 6.8 as blank. A graph of concentration (x-axis) vs. absorbance (y-axis) was plotted.

Formulation of Losartan Potassium Mucoadhesive Buccal Patches:

Method of preparation of patches:

Losartan potassium mucoadhesive buccal patches were fabricated by solvent casting method. Accurately weighed quantity of losartan potassium along with polymer was taken and dissolved in water consisting of polyethylene glycol 400 as plasticizer followed by stirring for 15 min until a clear solution was obtained and kept for refrigeration for 30 min. After complete removal of bubbles, the obtained solution was poured in petri plates. The petri plates were subjected to drying at room temperature for a period of 24 h by keeping the funnel in inverted position on the petri plates. Further, the developed patch was carefully peeled with the help of surgical scalpel by making a small cut in the patch on one side of petri plate. 4 cm² small patches were cut from a big patch and packaged in aluminium foil primarily and in a self- sealing polythene bag secondarily in order to ensure negligible moisture penetration and the patches obtained were evaluated⁷. A total of nine losartan potassium buccal patch formulations were developed and their composition was mentioned in Table 1.

Table 1: Formulation of mucoadhesive buccal patches of losartan potassium

Formulation code	Drug (mg)	HPMC K4M (%)	HPMC K15M (%)	HPMC K50M (%)	Eudragit L100 (%)	Polyethylene glycol 400 (ml)	Distilled water (ml)
F1	35	-	2	-	-	1	10
F2	35	2	-	-	-	0.5	10
F3	35	4	-	-	-	2	10
F4	35	-	-	2	-	2	10
F5	35	-	-	-	2	1	10
F6	35	-	4	-	-	2	10
F7	35	-	-	4	-	2	10
F8	35	-	2	2	-	0.5	10
F9	35	2	2	-	-	2	10

Calculationof dose of drug required per patch:

Dose of drug to be included in each 4cm²patch = 25mg of losartan potassium

Area of petri dish (Пr²) = 3.14*4.5*4.5 = 63.5cm²

No. of 4 cm²patches obtained from main patch = 9 patches each with 4 cm²area

Area of main patchtaken into consideration (9 patches) = l*b =6*6 = 36cm²

Area of patch not taken into consideration = total area - area considered = 63.5 - 36 = 27.5 cm²

Amount of losartan potassium in area taken into consideration = 9*25 = 225mg

Amount of drug in area not taken into consideration= 27.5*25/4 = 171.8mg

Total amount of losartan potassium to be included into a patch of 63.5 cm² = amount of losartan potassium in the area considered + amount of losartan potassiumin area not considered= 225 + 171.8 = 396.8mg

Evaluation of Losartan Potassiummucoadhesive Buccal Patches:

Physical evaluation of developed buccal patches:

Physical evaluation of prepared buccal patches was performed by visual inspection for the properties such as thickness, peeling ability, brittleness, surface smoothness, tackiness, transparency and film forming capability.

Thickness of patch:

Patch thickness was determined utilizing screw gauge with 0.01mm least count at various places on buccal patch. Thickness of patch was measured at three different places and average of thickness was measured⁸.

Weight variation:

For weight variation test, 3 patches of each formulation were randomly chosen and weight of every 2x2cm patch was measured separately on digital weighing balance. Further, average weight of patch was computed.

Surface pH:

In order to determine surface pH, three patches from each formulation were allowed in contact with 1ml of distilled water. Surface pH was mentioned by making a pH paper or combined glass electrodenear the surface of patches and allowed for 1 min to equilibrate. An average of 3 readings was recorded.

Folding endurance:

Folding endurance of prepared patches was decided by repeated folding of one patch at same place until it broke, measured satisfactory in order to disclose good patch characteristics. Number of times of patches could be folded at same place devoid of breaking provided the assessment of folding endurance. The test was performed for each formulation on randomly selected 3 patches⁹.

Drug content uniformity:

The drug content uniformity was established by dissolving a prepared patch of an area 4cm²,comprising losartan potassium in 50ml of phosphate buffer solution, pH 6.8 (simulated salivary fluid) with intermittent agitation. Filtration of solution was performed in order to take away insoluble residual matter, 1ml of filtrate was further diluted to 10ml with phosphate buffer solution, pH 6.8 (simulated salivary fluid). Absorbance was determined at λ_maxof 235nm utilizing UV-visible spectrophotometer. Experiments were performed in triplicate for patches of all formulations¹⁰.

Swelling study:

In case of swelling study, buccal patches of losartan potassium were individually weighted (W₁) and separately placed in 2% agar gel plates, exposed to incubation at 37^oC±1^oC, and checked for physical changes, if any. The fabricated buccal patches were examined at periodic time intervals of 1 h up to 3 h, and excess surface water was separated carefully utilizing filter paper¹¹. The swollen patches were further reweighed (W₂) and the swelling index was computed considering the following formula,

W₂ – W₁

Swelling Index of buccal patch = ------------- X100

W₁

Determination of % moisture loss:

Losartan potassium buccal patches were accurately weighed and stored in desiccators consisting of anhydrous calcium chloride. After 3 days, the buccal patches were taken out and reweighed. Percent moisture content was calculated by using the following formula¹².

(Initial Weight – Final Weight)

%Moisture Contend = -------------------------------- X 100

Initial Weight

In vitro residence/mucoadhesion time:

In vitro residence time of patches was analysed by knowing the time taken for buccal patch to get detached from goat’s buccal mucosa in a well stirred beaker filled with 500 ml of phosphate buffer, pH 6.8 at 37^oC. Mucosal membrane was secured on the side of beaker with the help of cyanoacrylate glue. Buccal patch was affixed to membrane by employing light force with the help of fingertip for the duration of 60 sec followed by magnetic stirring of beaker at a rate of approximately 150 rpm in order to simulate saliva and buccal movement. The time needed for the complete detachment or erosion of patches from mucosal membrane was considered as an indication of in vitro mucoadhesion time¹³.

Dispersion test:

A buccal patch equivalent to 25mg of losartan potassium was kept in phosphate buffer solution, pH 6.8 (200ml) and agitated for a time duration of 3 min. The resultant solution was passed through # 22 sieve. Buccal patch is stated to be passed dispersion test simply when no residual matter is left on sieve¹⁴.

In vitro drug release studies:

In vitro drug release studies were performed by means of Franz diffusion cell with freshly prepared egg membrane that functions as semi permeable membrane attached to one end of open cylinder represented as donor compartment. The fabricated buccal patches consisting of losartan potassium drug was kept within donor compartment. The receptor compartment composed of 100ml of phosphate buffer solution, pH 6.8 that is agitated continuously utilizing magnetic stirrer and further temperature was retained at 37^oC±1^oC. 2ml samples were withdrawn at periodical time intervals from the receptor compartment and substituted with fresh phosphate buffer solution, pH 6.8 instantly. Samples collected were filtered through a filter paperand then, assayed using UV-visible spectrophotometer at λ_maxof 235nm (Lab India). Rate of drug release was determined for all the prepared buccal patch formulations.

RESULTS AND DISCUSSION:

Pre-formulation studies of losartan potassium:

Drug and additives compatibility studies were examined by checking physical appearance and using instrumental analytical techniques such as FT-IR method of analysis.

Drug - excipient compatibility studies:

The interaction studies were carried out to ascertain any kind of interaction of drug with the excipients used in the preparation of losartan potassium mucoadhesive buccal patches.

Interpretation of losartan potassium:

Fig. 1: FT-IR spectra for losartan potassium

Fig. 2: FT-IR spectra for optimized losartan potassium buccal patch formulation (F6)

FTIR of pure drug – losartan potassium and formulation F6 were shown in Figures 1 and 2 respectively. The presence of characteristics peaks of drug OH (3198 cm^-1), CH stretching aromatic (3936.07 cm^-1), CH stretching aliphatic (3226.16 cm^-1) C=0 (2949.80 cm^-1), C=C (1638.64 cm^-1), C-O-C ether linkage (1108.85 cm^-1) in IR spectrum of formulation, indicated that there was no interaction of drug with the polymer and other excipients.

Formulation Development:

Standard curve of losartan potassium:

Calibration curve for losartan potassium was constructed at λ_max of 235nm in pH 6.8 phosphate buffer using UV-visible spectrophotometer which exhibited good reproducibility in the concentration range of 5 - 45 µg/ml. Correlation (R²= 0.999) between concentration and absorbance was observed to be nearer to 1 suggesting that the method followed Beer - Lambert's law.

Evaluation of Losartan Potassium Mucoadhesve Buccal Patches:

A total of nine losartan potassium mucoadhesive buccal patch formulations consisting of 25mg drug as dose per patch of 4 cm²area were fabricated by solvent casting technique with the use of mucoadhesive polymers such as HPMC K4M, HPMC K15 M, HPMC K50M and Eudragit L100 in different proportions.

The prepared patches were evaluated for physical characteristics, weight uniformity, thickness, surface pH, folding endurance, drug content uniformity, swelling index, water absorption capacity, dispersion test, in vitro residence time, % moisture content and in vitro drug release.

Physical characterization:

Physical characterization of patches was carried out by visual inspection and the following results were observed as given in Table 2.

Weight uniformity and patch thickness:

The weight of 4cm² patches of all formulations was found to be in the range of 207.47mg ±0.06 to 218.45 mg ±0.06, which was acceptable. Thickness of all patches was measured with Vernier calliper and thickness values for all formulations was in the range of 0.15mm±0.006 to 0.18mm±0.004 (Table 2). The optimized patch (F6) has thickness of 0.17mm±0.005.

Surface Ph:

For all the prepared patches, surface pH was determined and found to be between 6.41±0.005and 6.75±0.01, close to neutral pH as represented in Table 2, signifying that the buccal patches might possess lesser potential to irritate sublingual mucosa and hence, more patient compliance.

Folding endurance:

Results of folding endurance for the fabricated buccal patches were found to be in the range of 310±1.6 to 340 ±1.4 as mentioned in Table 2. Folding endurance of buccal patches formulation F6 was >300 which were as below mentioned that the prepared buccal patches of losartan potassium were ensuring great mechanical strength as well as good elasticity. Folding endurance was determined manually by repetitive folding of the patch until it broke, and the obtained value was deliberated as end point. Formulation, F2 demonstrated lowest folding endurance. Nevertheless, all buccal patch formulations exhibited adequate flexibility.

Table 2: Mechanical and physicochemical parameters of losartan potassium mucoadhesive buccal patches

Formulation code	Thickness (mm)	Weight uniformity (mg)	Surface pH	Folding Endurance	Drug content (%)	Swelling Index (%)
F1	0.18 ± 0.004	215.66 ± 0.04	6.63 ± 0.01	324 ± 1.2	90.32 ± 0.04	56.24 ± 0.04
F2	0.15 ± 0.006	210.53 ± 0.03	6.41 ± 0.005	318 ± 1.4	91.68 ± 0.06	57.33 ± 0.02
F3	0.17 ± 0.005	207.47 ± 0.06	6.71 ± 0.005	320 ± 1.0	90.97 ± 0.02	52.45 ± 0.06
F4	0.15 ± 0.006	218.33 ± 0.07	6.52 ± 0.005	310 ± 1.6	91.39 ± 0.06	60.80 ± 0.02
F5	0.17 ± 0.008	215.33 ± 0.05	6.75 ± 0.01	322 ± 1.4	93.50 ± 0.04	64.57 ± 0.08
F6	0.17 ± 0.005	218.45 ± 0.06	6.65 ± 0.001	340 ± 1.4	97.92 ± 0.02	68.29 ± 0.04
F7	0.16 ± 0.006	216.50 ± 0.08	6.52 ± 0.005	315 ± 1.2	90.85 ± 0.06	49.30 ± 0.06
F8	0.17 ± 0.005	214.67 ± 0.07	6.49 ± 0.01	326 ± 1.0	92.77 ± 0.02	51.17 ± 0.04
F9	0.18 ± 0.005	215.45 ± 0.05	6.64 ± 0.01	319 ± 1.6	94.26 ± 0.04	59.35 ± 0.08

Note: Mean ± SD of three determinations

Table 3: In vitro drug release profile for the prepared losartan potassiummucoadhesive buccal patches

Time (h)	% Cumulative drug release
Time (h)	F1	F2	F3	F4	F5	F6	F7	F8	F9
0	0	0	0	0	0	0	0	0	0
1	10.45 ± 1.21	11.23 ± 1.53	10.96 ± 1.46	12.45 ± 0.59	13.27 ± 0.12	13.83± 1.83	10.78 ± 1.75	13.45 ± 0.54	12.65 ± 1.59
2	18.94 ± 1.47	21.96 ± 0.65	22.64 ± 1.61	20.16 ± 1.81	23.49 ± 1.87	24.96 ± 1.86	19.74 ± 1.64	20.16 ± 1.51	17.16 ± 0.42
3	28.62 ± 0.68	29.45 ± 0.34	27.52 ± 0.17	31.40 ± 1.74	30.92 ± 1.39	33.45 ± 0.41	31.52 ± 1.19	30.04 ± 1.42	32.40 ± 1.44
4	55.94 ± 1.17	57.78 ± 1.67	57.74 ± 1.45	61.16 ± 1.48	54.49 ± 1.68	65.69 ± 1.64	51.74 ± 0.41	60.16 ± 0.72	58.16 ± 0.43
5	66.92 ± 0.68	67.45 ± 0.43	69.52 ± 0.38	67.40 ± 0.86	57.92 ± 0.57	69.45 ± 0.41	59.52 ± 1.06	64.40 ± 1.34	60.40 ± 0.64
6	72.36 ± 1.21	69.01 ± 1.38	70.18 ± 1.46	69.72 ± 1.32	65.36 ± 0.14	79.01 ± 1.28	62.18 ± 0.68	67.72 ± 0.28	65.72 ± 1.52
7	79.27 ± 1.47	70.47 ± 1.48	72.07 ± 0.73	72.46 ± 0.44	70.27 ± 1.45	80.47 ± 1.38	66.07 ± 1.52	72.46 ± 1.54	72.46 ± 1.32
8	88.18 ± 0.43	90.26 ± 0.90	93.94± 0.43	95.51 ± 0.96	96.18 ± 1.44	97.26 ± 0.41	94.94± 0.14	92.51 ± 0.96	89.51 ± 0.94

Note: Mean ± SD of three determinations

Drug content uniformity:

Based on the results of drug content uniformity, it was revealed that losartan potassium was dispersed uniformly and the values were found to be in the range of 90.32% ±0.04 to 97.77% ±0.02.

Swelling Index:

Swelling behaviour of mucoadhesive polymers used in buccal patches was analysed and results obtained were illustratedin Table 2. % Swelling index for buccal patches was observed in the range of 49.30% ± 0.06 to 68.29% ± 0.04.The void space was predicted to be occupied by an external solvent undergoing diffusion into buccal patch and thus hastening dissolution of gels. Among, all the formulations, the computed standard deviation values were observed to be very low which proposed that prepared buccal patches exhibited uniform swelling index.

Dispersion test:

For theprepared buccal patches, dispersion test was carried out and all formulations ensued that there was no residual matter left on sieve #22 after 3min.

In vitro dissolution studies:

For the developed formulations, in vitro dissolution studies were performed and results tabulated in Table 3 and Fig. 3. Buccal patch formulations F1 to F9 exhibited drug release in the range of 88.18 % ±0.43 to 97.26 % ±0.41 at the end of 8 h. Among all the formulations, F6 showed higher % of drug release 97.26% ± 0.41 at the end of 8h. Losartan potassium was observed to be released in a sustained manner for up to 8 h. Formulation F6, in which HPMC K15M was used as a polymer initiated burst release within 4 h. Based upon the drug release data obtained, formulation F6 was considered to be the best formulation.

Fig. 3: In vitro drug release profiles of prepared losartan potassium buccal patch formulations

CONCLUSION:

Losartan potassium mucoadhesive buccal patches were developed with the use of polymers like HPMC K4M, HPMC K15M, HPMC K50 M and Eudragit L100 and exhibited acceptable mucoadhesive and physicochemical characteristics. Based on the results obtained from the current research, it can be summarized that the fabricated mucoadhesive buccal patches may provide buccal delivery losartan potassium in a controlled manner for 8 h with enhanced bioavailability, permeability as well as therapeutic efficacy. Further, the investigation needs to be extended for ex vivo permeation studies, kinetics and in vivo drug release studies.

ACKNOWLEDGEMENTS:

The authors are thankful to Principal and Management of Chalapathi Institute of Pharmaceutical Sciences, Chalapathi Nagar, Lam, Guntur for providing necessary research facilities.

REFERENCES:

1. Hoogstrate AJ, Verhoef JC, Tuk B, Pijpers A, van Leengoed LA, Verheijden JH, Junginger HE, Boddé HE. In vivobuccal delivery of fluorescein isothiocyanate - dextran 4400 with glycodeoxycholate as an absorption enhancer in pigs. Journal of Pharmaceutical Sciences. 1996; 85(5): 457-460.doi: 10.1021/js950129k.

2. Patel KV, Patel ND, Dodiya HD, Shelat PK. Buccal bioadhesive drug delivery system: an overview. International Journal of Pharmaceutical and Biological Archive. 2011; 2(2): 600-609.

3. Jagadeeshwar Reddy R, Maimuna AA. Comprehensive review on buccal drug delivery system. American Journal of Alzheimer's Disease and Other Dementias. 2013; 1(3): 300-312.

4. Aungst A. Permeability and metabolism as barriers to transmucosal delivery of peptides and proteins. In: D.S.Hsieh (Ed.), Drug permeation enhancement. Theory and applications. Marcel Dekker, New York, 1994, 323-343.

5. https://go.drugbank.com/drugs/DB00678

6. Lippert C, Ling J, Brown P, Burmaster S, Eller M, Cheng L, Thompson R, Weir S. Mass balance and pharmacokinetics of MDL 16,455A in healthy male volunteers. Pharmaceutical Research. 1995; 12: S-390.

7. Khanna R, Agarwal SP and Ahuja A. Preparation and evaluation of mucoadhesive buccal films of clotrimazole for oral candida infections. Indian Journal of Pharmaceutical Sciences. 1997; 59: 299-305.

8. Merina A, Shajan A, Feba J, Haritha HP, Anu A, Elessy A, Dibyalochan M. Design and in-vitro evaluation of anagliptin buccal patch. Research Journal of Pharmacy and Technology. 2020; 13(8):3837-3842.

9. Arifa Begum Sk, Sravya AHLB, Deepika BGD, Naga Manasa G, Srujana M, Uma V, Lakshmi Tejeswari S, Padmalatha K. Formulation and evaluation of fexofenadine buccal mucoadhesive patches. Research Journal of Pharmacy and Technology. 2018; 11(11): 4892-4898.

10. Kumara SS, Shobha RS, Agaiah GB. Development, in-vitro and ex-vivo evaluation of muco-adhesive buccal patches of candesartan cilexetil. Research Journal of Pharmacy and Technology. 2019; 12(6): 3038-3044.

11. Maheswara RD, Madhusudhana CC, Dastagiri RY, Komali P,Divya SB, Sandhya RS. Formulation and Evaluation of fast dissolving buccal patches of tenofovir disoproxil fumarate. Research Journal of Pharmacy and Technology. 2021; 14(1):225-230.

12. Sussman GL, Mason J, Compton D, Stewart J, Richard N. The efficacy and safety of fexofenadine hcl and pseudoephedrine, alone and in combination, in seasonal allergic rhinitis. Journal of Allergy and Clinical Immunology. 1999; 104(1): 100-106.

13. Torrado JJ and Augsberger LL. Tableting of multi-particulate modified release systems. in: pharmaceutical dosage forms – tablets vol. 2. rational design and formulation(AugsbergerLL and Hoag SW. Ed.). 2008, 3rd Ed., Informa Healthcare, London, Pg. No. 509-533.

14. Sarojini S, Manavalan R, Priyadarsini S. Study of effect of solubility of drug on the release behaviour from buccal films of a hydrophilic polymer. Research Journal of Pharmacy and Technology. 2010; 3(1): 227-230.

Received on 22.04.2021 Modified on 29.12.2021

Research J. Pharm. and Tech 2023; 16(7):3151-3156.

DOI: 10.52711/0974-360X.2023.00518