INTRODUCTION:

Transdermal drug delivery system (TDDS) are a non-invasive technique for putting drugs under the skin that keeps therapeutic dosages effective and long-lasting by inhibiting biotransformation¹. These systems apply autonomous, discrete dose forms to healthy skin, allowing the drug to enter the bloodstream at a predefined rate.

TDDS improves patient compliance and prevents first-pass metabolism compared to injectable and oral methods. Advantages include being advantageous for mentally disabled patients, avoiding first-pass metabolism, being convenient, reducing dosage frequency, and reducing side effects^2-3. However, TDDS has disadvantages such as potential for medications with hydrophilic properties to not be effective at therapeutic levels, causing local itchiness and edema, and varying skin barrier function. High drug concentrations in the blood or plasma cannot be reached with TDDS, and drugs with large molecular weights cannot be made using this approach. TDDS is also not suitable for pulsatile medication delivery. Transdermal patches are pliable pharmaceuticals available in various sizes, containing active ingredients that cross the skin's barriers and enter the bloodstream⁴.

Transdermal patches offer benefits such as increased systemic bioavailability, continuous drug infusion, no gastrointestinal juice alteration, predictable action duration, simple application and handling, and non-invasive, steady drug penetration. However, they may induce allergic reactions, be cost-effective, and only deliver highly potent API due to skin impermeability. Ionic medications may cause issues, and drugs with low or high partition coefficients may not be absorbed into the systemic circulation⁵.

Physiological and pathological conditions of the skin also influence how much medication can penetrate the skin. Hydration reduces skin swelling, increases skin temperature, and can have harmful effects on middle-aged and younger people. Blood flow changes in transdermal absorption do not affect peripheral circulation, as drug molecules persist in the dermis, enhancing the concentration gradient. In conclusion, TDDS involves various factors that influence the absorption of medications through the skin. These factors include the drug's physiochemical properties, formulation characteristics, and skin physiology and pathology. By understanding these factors, TDDS can effectively manage drug delivery and maintain effective drug delivery^6-7.

A strong oral antiplatelet drug, clopidogrel bisulfate is frequently used to treat peripheral vascular disease, cerebrovascular disease, and coronary artery disease. A medication used to treat platelets, clopidogrel bisulfate has a 50% oral bioavailability and is metabolized first in the liver. That makes it appropriate for transdermal patch formulation. Three possible routes exist for drug molecules in touch with the skin's surface: Directly via the stratum corneum, through the sweat ducts, and through hair follicles and sebaceous glands^8-9.
Using different polymers, including HPMC K4M, Eudragit -L-100, and PEG-400, using solvent evaporation technique, the present study effort aimed to design, develop, and characterize a transdermal drug delivery system for clopidogrel bisulfate^10-11.

MATERIALS AND TECHNIQUES:

Modern Industries kindly provided a gift sample of clopidogrel bisulfate, Arti drugs-LTD, PEG -400, and HPMC K4m, Eudragit L-100, and all other laboratory chemicals used in the research work were analytical grade.

Procedure for formulation of Transdermal Patches:

The solutions of both the polymers HPMC K4M and Eudragit L- 100 were prepared by blending HPMC K4M in 10 ml of Methanol and Eudragit L- 100 in 10ml of Dichloromethane. Mix mixture of dichloromethane solution of Eudragit L-100 in methanolic solution of HPMC K4M by the side of the beaker. Put the solution stable to remove the bubbles for 30 min. After, add weighed quantity of clopidogrel bisulfate in that mixture and blend properly to solubilize drugs. Again, put solution stable to remove bubbles for 20min. Then add polyethylene glycol in it and stable it for 10min. In order to allow the solvent to evaporate, after adding the solution to the petri dish, it was allowed to dry for 24 hours at room temperature. You may adjust how much of the solvent evaporation happens by flipping the plate funnel over to the petri dish. 24hours later patches were scraped off, allowed to dry for two to four days, and then cut into circles. These patches were put in desiccator and wrapped in aluminium foil^12-16.

Transdermal Patch Evaluation:

Physical characteristics:

All created patches were visually inspected for color, clarity, flexibility, and smoothness.

Weight Variation:

A specified patch area should to be separated into several sections, each of which needs to be weighed on a digital scale independently. The average weight should be determined using the individual weights¹⁷.

Folding Endurance:

A certain area's strip was cut uniformly, folded precisely each time, and then broken. The number of folds the film could withstand before cracking was used to gauge its folding strength¹⁸.

Thickness:

With a screw gauge that is digitally micrometer (Vernier Caliper), patch thickness was measured three times, and the calculation of the mean value¹⁸.

Table 1: Optimization batches developed by 3² factorial designs

Formulations Ingredients	F1	F2	F3	F4	F5	F6	F7	F8	F9
Clopidogrel bisulfate (mg)	20	20	20	20	20	20	20	20	20
Hydroxypropyl methyl cellulose K4M (mg)	400	400	400	350	350	350	300	300	300
Eudragit L -100 (mg)	300	250	200	300	250	200	300	250	200
Methanol (ml)	10	10	10	10	10	10	10	10	10
Dichloromethane (ml)	10	10	10	10	10	10	10	10	10
polyethylene glycol-400 (ml)	5	5	5	5	5	5	5	5	5

Drug Content:

To measure the amount of medication, a 1x1 cm2 patch was fully dissolved in 10ml of pH 7.4 phosphate buffer solution. Complete breakdown was attained by placing the patch with the solution on a shaker for around 24 hours. Following the proper dilution, the solution was filtered, Spectrophotometry was used to measure the drug's concentration at a wavelength of 254nm^19-21.

Surface pH:

A pH metre was used to measure the transdermal patch's surface pH. Patch received some moisture from the water. Placing the electrode directly on the patch's surface allowed for the measurement of pH. The results were released as an average after the process was carried out three times²².

Percentage Moisture Absorption:

The purpose of the absorption of water test was to evaluate the patches' physical integrity and stability in excessively humid environments. In this experiment, the patches' capacity to accept moisture was evaluated in the manner described below. The patches were placed within a desiccator with an internal humidity of 80% R.H. and a fully saturated solution of aluminium chloride. The films were taken out and weighed after three days to find out how much moisture each of the three films had absorbed. The proportion of moisture absorbed was determined using the formula below²³.

Final weight – Initial weight

Percentage Moisture = -------------------------------- × 100

Absorb (%) Initial weight

Percentage Moisture Loss:

The resulting patches were weighed separately and stored in a desiccator with fused calcium chloride for a full day at room temperature. The patches were weighed once more a day later, and the method outlined below was used to calculate the percentage of total moisture loss²⁴.

Initial weight − Final weight

Percentage Moisture Loss (%) = --------------------- ×100

Initial weight

Swellability:

One-centimetre-squared patches were immersed in filtered water for half, an hour, two hours, four hours, and a total of 24hours. Films that had been soaked were removed from the medium at the proper time, washed to get rid of extra liquid, and then immediately weighed. The weight increase in the operation was used to construct the swelling index, as shown below²⁵.

Final weight - Initial weight

Swellability (%) = ------------------------------------- ×100

Initial weight

In-vitro Drug Release Study:

For in vitro drug diffusion studies, the 20ml Franz diffusion cell was employed. The membrane of the egg gave rise to the skin. The membrane was stabilized prior to attachment in order to remove the associated parts. The membrane was positioned between the donor and receptor compartments. Twenty milliliters of pH 7.4 phosphate buffer, maintained at 37±0.2°C, were added to the receptor compartment. Hydrodynamics was preserved during the introduction of magnetic beads by means of a magnetic stirrer. Patch was soaked with a few drops of pH 7.4 phosphate buffers before being placed into the donor compartment.

One milliliter samples from the receptor compartment were taken out and replaced with one milliliter of pH 7.4 phosphate buffer at the proper intervals of 1, 2, 3, 4, 6, 8, and even twelve hours. The absorbance at a maximum of 254nm is measured with a UV-visible spectrophotometer, and the amount of medications that penetrate was determined^26-28.

Solubility study:

Estimating the approximate parts (ml) of any solvent needed to dissolve one part (gm) of solute (drug) yields the solubility. Following the IP standard solubility protocol, the solubility of the medications clopidogrel bisulfate was examined in a variety of solvents, including methanol, ethanol, a solution of phosphate buffer (pH 7.4), and distilled water. A precise dosage of each medication (10mg) was dissolved in 10 ml of each solvent at room temperature. Visual analysis provides soluble^9-11.

RESULTS AND DISCUSSION:

Effect of Independent factor on wet mass:

3² factorial design was used for the optimization. F1 through F9 batches of Eudragit L100 and HPMC K4M polymer concentrations were made and analysed. In the optimization investigation, the polymer and HPMC K4M concentrations were divided into three levels: low, medium, and high. Key considerations in this investigation were the effects of three dependent parameters % Moisture uptake, % cumulative drug release at 2hours, and % 12hour on the independent factors, HPMC K4M and Eudragit L-100. This impact aids in selecting the best batch from the nine formulations. Utilizing the Stat-Ease 360 program, a multilevel categoric linear regression approach under ANOVA investigation was utilized to ascertain fit statistics, coefficient values, and optimization data for analysis of variance. This phenomenon may be explained by the combination of clopidogrel bisulfate, which inhibits its release at low pH values, and the presence of Eudragit, which ionizes at alkaline pH and causes the drug's release to increase at that point. At this time, the release was significantly antagonistic to HPMC K4M (p = 0.0001) and Eudragit L-100 (p = 0.0025). Results implies the release of clopidogrel bisulfate from the patches was enhanced by raising the amount of Eudragit at the middle stage. According to the response surface, At the smallest amounts of Eudragit L-100 along with HPMC K4M.Utilizing a variety of distribution kinematics designs, the mechanism of clopidogrel bisulfate release in the tested transdermal patches formulations has been studied at release periods of 12 hours with pH 7.4.

ANOVA:

ANOVA to compare three models, one uses the Analysis of Variance. It is helpful when looking at two or more variables, generally speaking. ANOVA is typically used to compare the average outcomes at various factor levels. 9figure-1, 2 and 3).

Table 2: 3² Factorial design with factors and responses

Batch No.	Factor 1	Factor 2	Drug	Response 1	Response 2	Response 3
Batch No.	A: HPMC (mg)	B: Eudragit L-100 (mg)	Clopidogrel Bisulfate (mg)	Moisture Uptake (%)	Drug release of at 2 hour (%)	Drug release of at 12 hour (%)
F1	400	300	20	4.791	1.008	62.98
F2	400	250	20	4.085	0.934	68.13
F3	400	200	20	3.710	0.734	65.42
F4	350	300	20	3.176	1.774	60.38
F5	350	250	20	2.821	2.1798	75.913
F6	350	200	20	1.812	1.361	67.23
F7	300	300	20	1.724	0.945	59.36
F8	300	250	20	1.534	6.811	51.3
F9	300	200	20	1.228	0.638	35.382

ANOVA for Linear Model

Fourier Transform Infrared (FTIR) Spectroscopy:

FT-IR spectroscopy is among the most potent analytical methods that may be used for chemical identification and verification. The following shows the different FT-IR absorption zones of significant bands required for the clarification of drugs and excipients. (Figure-4).

Drug Content:

The drug content of clopidogrel bisulfate was found in between 88.12-98.78%. The F5 had highest drug content of clopidogrel bisulfate and F1 and F8 had lowest drug content of clopidogrel bisulfate.

Table 3: Percentage drug content of Clopidogrel Bisulfate

Sr. No.	Formulation Code	Drug Content (%)
Sr. No.	Formulation Code	Clopidogrel Bisulfate
1.	F1	88.12%
2.	F2	96.54%
3.	F3	92.18%
4.	F4	93.81%
5.	F5	98.78%
6.	F6	95.33%
7.	F7	94.33%
8.	F8	92.27%
9.	F9	94.64%

Thickness:

The thickness of every film was found to be the same for every formulation. the material's thickness varied from 0.36mm to 0.72mm.

Folding Endurance:

The study showed that most of the batches did not shatter even after being folded 250 times, indicating that they had strong elasticity and could withstand ordinary skin folding. The findings showed that patches of batches F6, F8 and F9 shows folding endurance less than 200. The F1 had highest folding endurance and F9 had lowest folding endurance which was 251 and 135 respectively.

Percentage Moisture Absorption:

The results indicate that the percentage moisture uptake for HPMC -Eudragit L-100 ranged from 1.22% to 4.79%. These results may be related to the hydrophilic and hydrophobic characteristics of the polymer.

Percentage Moisture Loss:

The patches remained stable and became a totally free from becoming completely dry and brittle which also protects the material against microbial contamination due to the decreased moisture content in the formulations, the percentage moisture loss of patches was found in range of 1.32% to 3.96%.

In-Vitro Drug Release Study:

Diffusion profiles of transdermal patch batches show that this is caused by Eudragit L-100's hydrophobic polymer. The drug release from patch is regulated for a duration of 12 hours. The amount of control drug released by transdermal patches is dependent on several factors, including the physiological and physicochemical qualities of the biological membrane, the chemical properties of the medication, and the delivery method. for clopidogrel bisulfate, for all formulations, the 12-hour total amount of drug release ranged from 35.38% to 75.91%.

Figure 5: % cumulative drug release of F1 to F9 batches of clopidogrel bisulfate

Steady State Flux:

The steady state flux for all formulations range from 0.609μg/cm² 12hr-2.922μg/cm² 12hr for Clopidogrel Bisulfate. The steady state fluxes for the drug were highest for F5 batch.

Stability Study of Optimized Formulation:

The optimised transdermal patch (F5) completed three months of stability testing, and it was found that there had been no significant alterations to the drug content, in vitro drug release. The findings showed that optimized transdermal patch (F5) was steady.

Kinetic Study:

By examining release data using several kinetic equations, the kinetics of drug release from the chosen patch formulation (F5) was examined. Regression coefficient analysis was used to examine the data. Regression coefficient results were evaluated and it was observed that the F5 formulation for clopidogrel bisulfate had zero order kinetics with R² = 0.9228. One may also use the first order equation with R² = 0.9401 to depict the drug release characteristics from these formulations in vitro. The diffusion mechanism was subsequently confirmed by fitting Korsemeyer Peppa's equation to the data. The formulation demonstrated good linearity because of the respective R² values of 0.6377 for clopidogrel bisulphate. Applying the Higuchi model to this formulation of clopidogrel bisulfate yielded an R² of 0.7356.

Figure 6: Kinetic Study plot of Korsemeyer Peppa’s Drug Release Mechanism

CONCLUSION:

Clopidogrel bisulfate, a drug that inhibits ergosterol manufacture, is used to treat gastrointestinal issues. A study developed a transdermal patch for this drug, using nine formulations made from film-forming polymers Eudragit L-100 and HPMC K4M. The patches were tested for weight, drug content, moisture content, thickness, folding endurance, and in vitro diffusion study. The results showed that the patches, when combined with polymers, showed good mechanical and physical properties. The F5 formulation had the highest drug release and moisture content, making it highly effective in preventing microbiological contamination and patch bulkiness. The drug content was within predetermined ranges, and the optimal formulation was found to have the highest steady state flux. The patch underwent three months of stability testing, with no significant changes in drug content or in-vitro release. Further studies are recommended to determine the therapeutic utility of transdermal patches of Clopidogrel Bisulfate in humans through pharmacokinetic and pharmacodynamic studies.

CONFLICT OF INTEREST:

The authors have no conflicts of interest regarding this investigation.

ACKNOWLEDGMENTS:

The authors express their sincere thanks to Modern Industries, Arti Drugs-Ltd., India for supplying gift samples of clopidogrel bisulfate as an Active Pharmaceutical Ingredient. The authors are thankful to GES’s Sir Dr. M. S. Gosavi College of Pharmaceutical Education and Research, Nashik, MS, India for providing the facility to carry out the research work.

REFERENCES:

1. Ashfaq A, Riaz T, Waqar MA, Zaman M, Majeed I. A comprehensive review on transdermal patches as an efficient approach for the delivery of drug. Polymer-Plastics Technology and Materials. Research Journal of Pharmacy and Technology. 2024; 8: 1045-69. doi.org/10.1080/25740881.2024.2317408

2. Sanjay A. Nagdev, Omprakash Agrawal, Md. Rageeb Md. Usman. Transdermal Drug Delivery System: An Overview. Research Journal of Pharmacy and Technology. 2022; 15(3): 1371-7. doi: 10.52711/0974-360X.2022.00229.

3. Bharadwaj S, Garg VK, Sharma PK, Bansa M, Kumar N. Recent advancement in transdermal drug delivery system. International Journal of Pharma Professional’s Research (IJPPR). 2011; 2(1): 212-9. https://doi.org/10.3109/03639045.2011.652635

4. Takmaz E.A, Inal O, and Baykara T. Studies on transdermal delivery enhancement of Zidovudine. AAPS Pharm Sci Tech. 2009; 10(1): 89-97. https://doi.org/10.1208/s12249-008-9179-9

5. Singh A, Bali A. Formulation and characterization of transdermal patches for controlled delivery of duloxetine hydrochloride. Journal of Analytical Science and Technology. 2016; 7(1): 1-3. https://doi.org/10.1186/s40543-016-0105-6

6. Kulkarni RV, Mutalik S, Hiremath D. Effect of plasticizers on the permeability and mechanical properties of Eudragit films fortransdermal application. Ind J Pharm Sci. 2002; 64(1): 28-31. DOI: 10.52711/0974-360X.2023.00349

7. Darwhekar G, Jain DK, Patidar VK. Formulation and evaluation of transdermal drug delivery system of clopidogrel bisulfate. Asian J Pharm Life Sci. 2011; 2231: 4423. DOI: https://doi.org/10.22377/ajp.v10i1.527

8. Mukherjee B, Kanupriya MS, Das S, Patra B. Sorbitan monolaurate 20 as a potential skin permeation enhancer in transdermal patches. J Appl Res. 2005; 1: 96-108. https://doi.org/10.1080/17425247.2020.1713087

9. Boddeda B, Suhasini MS, Niranja P, Ramadevi M, Anusha N. Design, evaluation and optimization of clopidogrel bisulfate transdermal patch by 22 factorial method. Der Pharmacia Lettre 2016; 8(5): 280-7. DOI: 10.52711/0974-360X.2023.00349

10. Monika M, K. Krishna Prema. Phytochemical analysis of commercially available Spirulina, their activities and Biosynthesis of transdermal patch. Research Journal of Pharmacy and Technology. 2021; 14(12): 6189-3. DOI: 10.52711/0974-360X.2021.01071

11. Keerthi Priya J, Prem Kumar P and Shameera Begum SK: Formulation and evaluation of clopidogrel bisulphate transdermal patches using polymers as permeation enhancer. Int. J Pharm Sci. Res. 2014; 5(2): 473-482. DOI: 10.13040/IJPSR.0975-8232.9(1).250-55

12. Chauhan SB. Comparative Analysis of Penetration Enhancer on Transdermal Drug Delivery of Antifertility Drugs. Research Journal of Pharmacy and Technology. 2020; 3: 1457-62. DOI: 10.52711/2321-5844.2023.00015

13. Bhattacharyya S, Nanjareddy L. Assessment of Nano Lipid Carrier Loaded Transdermal Patch of Rizatriptan Benzoate. Drug Metabolism and Bioanalysis Letters Formerly: Drug Metabolism Letters. 2022; 2: 101-15. Research Journal of Pharmacy and Technology. DOI: https://doi.org/10.2174/2949681015666220609095706

14. Mohapatra PK, Kumar BP, Patel PS, Verma HC, Sahoo S. Development and Evaluation of Trans Buccal Patches based on Natural and Synthetic Polymers Loaded with Rivastigmine using Solvent Casting Technique. Research Journal of Pharmacy and Technology. 2021; 14(10): 5133-40. DOI: 10.52711/0974-360X.2021.00894

15. Pooja Dhama, Sachin Kumar, Manoj Kumar Sagar. Development and Characterization of Transdermal patches of Tramadol Hydrochloride: An Approach to Pain Management. Research Journal of Pharmacy and Technology. 2022; 15(1): 1-5. DOI: 10.52711/0974-360X.2022.00001

16. Lama Alhaushey, Ranin Darwish Ahmad. Formulation and Evaluation of Celecoxib Transdermal Patches. Research Journal of Pharmacy and Technology. 2023; 16(4): 1574-0. DOI: 10.52711/0974-360X.2023.00257

17. Ragni Kumari, Virendra Kumar Sharma. Optimization of the Formulation of Transdermal patches of Amiodarone. Research Journal of Pharmacy and Technology. 2023; 16(8): 3739-2. DOI: 10.52711/0974-360X.2023.00617

18. Prerana Sahu, Anjali, Gyanesh Kumar Sahu, Harish Sharma, Chanchal Deep Kaur. Formulation, Characterization and Ex vivo Evaluation of Epinephrine Transdermal Patches. Research J. Pharm. and Tech. 2020; 13(4): 1684-1692. DOI: 10.5958/0974-360X.2020.00305.4

19. Sidra Choudhary, Sanket Dharashivkar, Chetan Mahajan, Madhuri Gaikwad. Formulation and Evaluation of Nano-fiber-based Transdermal patch of Cephalexin. Research J. Pharm. and Tech 2020; 13(6): 2787-2791. DOI: 10.5958/0974-360X.2020.00495.3

20. Naaz F, Majumdar A, Malviya N, Mourya P, Dhere M. Formulation and Evaluation of Febuxostat Transdermal Patch for Management of Gout. Evaluation. 2024; Jan 19; 1(1): 1. DOI: 10.52711/0974-360X.2024.00058

21. Liji Jacob, Manju Salim S, Jilby Saju. Formulation and Evaluation of Transdermal Patches of Selegiline. Asian Journal of Pharmacy and Technology. 2022; 12(2): 96-0. DOI: 10.52711/2231-5713.2022.00016

22. Kalpak Gajbhiye, Nawaz Hakam, Gauri Rathod, Mukund Tawar. Formulation and Evaluation of Transdermal Patches of Benidipine Hydrochloride. Asian Journal of Pharmacy and Technology. 2021; 11(3): 207-2. DOI: 10.52711/2231-5713.2021.00034

23. Rajasekhar B, Reddy BH, Farheen GA, Anjinappa J, Krishna KR, Srilatha P, Farida S. Formulation and evaluation of transdermal patch of carbamazepine. World Journal of Advanced Research and Reviews. 2024; 22(2): 1601-11. DOI: https://doi.org/10.30574/wjarr.2024.22.2 1549

24. Tadhi N, Chopra H, Sharma GK. Formulation and Evaluation of Transdermal patch of Methimazole. Research Journal of Pharmacy and Technology. 2021; 14(9): 4667-72. DOI: 10.52711/0974-360X.2021.00811

25. Satyalakshmi S, Karthik D, Anusha J, Kamala Kumari PV, Srinivasa Rao Y, Rama Rao B. Design, characterization and optimization of Rosuvastatin calcium nanosponges loaded transdermal patch. Research Journal of Pharmacy and Technology. 2024; 17(4): 1753-7. DOI: 10.52711/0974-360X.2024.00278

26. Himani Bajaj, Seema Bisht Chauhan, Mayank Yadav, Navin Chandra Pant, Mamta Farswan Singh, Vinod Singh. Non-Aqueous Based HPMC Transdermal Patch of Aceclofenac: In vitro characterization. Research Journal of Pharmacy and Technology. 2024; 17(3): 1107-3. DOI: 10.52711/0974-360X.2024.00173

27. Farheen Naaz, Arti Majumdar, Neelesh Malviya, Priya Mourya, Manisha Dhere. Formulation and Evaluation of Febuxostat Transdermal Patch for Management of Gout. Research Journal of Pharmacy and Technology. 2024; 17(1): 373-8. DOI: 10.52711/0974-360X.2024.00058

28. Kamal Kumar, Nida Parveen. Development of Nanoparticles of an Antifungal Drug Incorporated in Transdermal patch. Research Journal of Pharmacy and Technology. 2023; 16(5): 2125-2. DOI: 10.52711/0974-360X.2023.00349

Received on 06.07.2024 Revised on 15.01.2025

Accepted on 21.05.2025 Published on 01.12.2025

Available online from December 06, 2025

Research J. Pharmacy and Technology. 2025;18(12):5626-5632.

DOI: 10.52711/0974-360X.2025.00812

This work is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License. Creative Commons License.