FORMULATION AND CHARACTERIZATION OF CLOZAPINE ADHESIVE PATCHES USING VARIOUS PRESSURE SENSITIVE ADHESIVES AND PERMEATION ENHANCERS

FORMULATION AND CHARACTERIZATION OF CLOZAPINE ADHESIVE PATCHES USING VARIOUS PRESSURE SENSITIVE ADHESIVES AND PERMEATION ENHANCERS

Milan B. Agrawal ^* and Mayur M. Patel

Department of Pharmaceutics, Institute of Pharmacy, Nirma University, SG Highway, Chharodi, Ahmedabad - 382481, Gujarat, India.

ABSTRACT: The present research work was intended to develop and characterize the transdermal adhesive patch of clozapine using different types of acrylate, polyisobutylene and silicon adhesives. Various permeation enhancers such as 1, 8 – cineole, D-limonene, Azone, IPM and Oleic acid were also evaluated to achieve desired permeation rate and hence to attain the improved bioavailability as compared to oral formulation. Formulation prepared were evaluated for physicochemical characterization, FTIR, DSC, permeability enhancement potential by ex-vivo, and stability studies. The results of the optimized formulation showed peel strength of 411 ± 3.56 cN/cm, flux of 109.59 ± 1.59 (µg/h/cm²) and % drug content of 99.53 ± 0.42% which was stable up to six months in accelerated condition. The results of the study revealed that the developed transdermal patch of clozapine can be a promising alternative which provides effective management of schizophrenia in terms of improved patient compliance and bioavailability which in turn reduces the dosage frequency and hurdles associated with the caretakers and doctors.

Pressure sensitive adhesives, Atypical antipsychotic, ex-vivo permeation, Permeation enhancers, Transdermal drug delivery

INTRODUCTION: Schizophrenia is characterized by disintegration of thought processes and of emotional responsiveness. It is a severe form of mental illness affecting about 21 million people worldwide ^{1, 2}. Clozapine is taken twice daily, orally, in the form of tablet. However, when taken by oral route, it undergoes extensive first pass metabolism and oral bioavailability of clozapine is reported to be less than 27% ³. Clozapine is extensively metabolized by hepatic microsomal enzymes (CYP1A2 and CYP3A4) and forms N-demethyl and N-oxide metabolites.

These makes delivery of clozapine, a challenging task for the efficacious therapy of nervous disorders such as schizophrenia, where prolonged drug delivery is essential for the people who may need assistance to receive medication by oral or by parenteral route. The topical drug delivery provides various benefits as compared to traditional dosage forms viz. improved compliance of patients on long-lasting therapy, maintaining a prolonged and constant plasma level of drug (thereby diminishing the side effects associated with the oral route), bypassing biotransformation, reducing inter and intra-patient variability and making it possible to put an end to drug therapy whenever needed ⁴.

MATERIALS AND METHODS:

Materials: Clozapine was given as a gift sample by Piramal Enterprises Ltd. India. Different grades of pressure-sensitive adhesives (PSA), release liners and backing membranes were procured from Henkel Corporation and 3M Healthcare. Isopropyl myristate (IPM) was purchased through Triveni Interchem Pvt. Ltd., Vapi, India. D-limonene and oleic acid were purchased from A.B. Enterprises, Mumbai, India. 1, 8-Cineole was purchased from Sanket Enterprises, Mumbai, India. Other reagents and chemicals used in the research were procured from reliable and standard sources.

Formulation of Transdermal Patches: ^{5, 6} Transdermal patches of clozapine were prepared by the solvent casting technique. Clozapine was dissolved in a concentration of 20% w/w along with pressure-sensitive adhesive (DT-387-2510) in a solvent system of ethyl acetate. In addition to this oleic acid (12.5% w/w of dry polymer weight) as permeation enhancer was added to the above solution. To prepare homogeneous dispersion, the mixture was continuously stirred for 30 min and poured on a release liner (Scotch pack 1022, 3M, USA). The patch was kept at room temperature for 10 minutes and then dried in oven at 50 °C for 5 min and laminated with backing membrane (Scothpack 9723, 3M, USA).

Evaluation of Transdermal Patches:

Physical Characterization: The prepared transdermal patches (4.41 cm²) were evaluated for weight variation by digital electronic balance (Mettler Toledo, Ohio, USA).The thickness of the patch was measured by using a digital vernier calliper (Mitutoyo, Japan) at random points ⁷. Peel strength was determined by loyd universal testing machine (LRX+) (Testometric, Rochdale, United Kingdom) ^{8, 9}. Drug content was quantified by dissolving the patch of size 4.41 cm² in 100 mL of methanol, which was then analyzed spectrophoto-metrically at a wavelength of 259 nm ¹⁰.

Ex-vivo Permeation Study: The ex-vivo permeation studies were carried out in vertical Franz diffusion cell using Wistar rat skin (Approval no. ROFEL/IAEC/2018/3) after detaching the adhering fat and hair. The formulation was fixed on the skin in such a way that the drug matrix was facing the donor side. Phosphate buffer (pH 7.4) was used as receptor fluid maintained at a temperature of 32 ± 0.5 ºC along with the agitation speed of 50 rpm. At different time intervals, the samples were withdrawn and exchanged with equal amounts of fresh media. Aliquots were analyzed spectrophotometrically at a wavelength of 259 nm ¹¹. The drug permeated per cm of the patch was given as per the following equation and plotted against time and the flux was calculated as drug permeated per cm² per hour ¹².

…..(1)

Where C_n is the receiver solution concentration of drug, C_i is the i_th sample drug concentration, V₀ and V_i are the receptor medium volume and sample volume, respectively, while S is the effective area of diffusion ¹³.

Interaction Studies: The interaction studies were performed for finalized batch by doing comparison of the clozapine, PSAs, and a mixture of clozapine and PSAs based on FTIR (Jasco 1800, Tokyo, Japan) and DSC (Shimadzu 60A, Kyoto, Japan) studies ¹⁴.

Stability Study: The accelerated stability testing study of the optimized transdermal patch was performed for 6 months, according to the ICH guidelines ¹⁵. Adequate replicates of the optimized patch were composed and stability study was carried out at temperatures of 40 ± 2 ºC and 75 ± 5% Rh for six months. Samples were withdrawn at an interval of 1, 3 and 6 months and drug content, flux, and peel strength analyzed for the stability samples and results were compared with freshly prepared patches ¹⁶.

RESULTS AND DISCUSSION:

Selection of Pressure Sensitive Adhesives: Based on the type and different physicochemical properties polyisobutylene, silicon and acrylate adhesives are selected for the study. Acrylate adhesives used for the study were based on functional groups, crosslinkers, vinyl acetate and viscosity of PSA Table 1.

The target skin permeation rate for Clozapine was calculated using the following equation ¹⁷

J = (Cl × Cp × W)/A ....(2)

Here, J corresponds to the flux (µg/h/cm²), A is the patch surface area (4.41 cm²), Cp corresponds to the plasma concentration (100 µg/L), Cl is the rate of clearance (0.072 L/h/kg) and W is the weight of the patient (considered as 60 Kg) ¹⁸.

The theoretically required flux for Clozapine as calculated from the above equation was found 97.95 µg/h/cm² which considered as ~100 µg/h/cm². The permeation rate is necessary for attaining the adequate plasma concentrations of the drug. Initially, for the screening of PSA, batches were prepared with 15% drug loading. This factor was kept constant to assess the impact of adhesive on drug permeation.

It was depicted from the results Table 2 that flux for DT-87-6908 (polyisobutylene) and Bio-PSA 7-4302 (silicon) was found to be 16.84 ± 1.34 µg/h/cm² and 13.56 ± 2.71 µg/h/cm² respectively while for DT-87-9301 and DT-87-4098 (acrylate) it was found to be 20.42 ± 3.42 µg/h/cm² and 28.13 ± 1.67 µg/h/cm² respectively.

TABLE 1: SELECTION OF PSA BASED ON THEIR PHYSICOCHEMICAL PROPERTIES

Here all above mentioned PSAs having no functional groups attribute that acrylate adhesives are having higher flux than polyisobutylene and silicon adhesives.

Flux for DT-387-2287, DT-387-2516 and DT-387-2510 was found to be 31.65 ± 0.23 µg/h/cm², 34.91 ± 1.37 µg/h/cm² and 44.13 ± 1.08 µg/h/cm² respectively Fig. 1. Here above mentioned, three acrylates are consisting of –OH (hydroxyl) functional group where flux for DT-387-2287 was found least in this –OH functional group category. This was attributed to its highest viscosity of 18000 mPa.s while in the case of DT-387-2516 and DT-387-2510 former was slightly lesser due to the presence of cross-linkers while the same is absent in case of DT-387-2510.

Now in case of DT-387-2353, DT-387-2852 and DT-387-2052 acrylate adhesives with –COOH (Carboxyl acid) functional group the flux was found to be 8.16 ± 2.19 µg/h/cm², 10.31 ± 1.46 µg/h/cm² and 11.26 ± 1.11 µg/h/cm² respectively. Hence the flux found highest with –OH functional group was might be due to its characteristic of reducing the drug-tissue binding by occupying hydrogen bonding sites and giving the solvating effect of alpha-keratinin within corneocytes which leads to the marginal increase in lipid fluidity and hence the drug permeability.

So, it improves the solubility of the drug within stratum corneum and resulting in increased drug partition into the skin.

TABLE 2: PHYSICO-CHEMICAL CHARACTERIZATION OF CLOZAPINE TRANSDERMAL PATCH

(mean ± SD, n=3)

According to literature peel strength, less than 300 cN cm^-1 leads to poor adhesion, as shown in results peel strength was found greater than the mentioned criteria for all the adhesives. So, based on the result and discussion DT-387-2510 was selected for further studies.

FIG. 1: EFFECT OF DIFFERENT PSA ON EX-VIVO SKIN PERMEATION

Optimization of Drug Loading: To determine the optimum concentration of clozapine, different batches A1 to A4 prepared with drug loading in a range of 10% - 30% to check its impact on skin permeation. It was depicted from the results that Table 3 as the concentration of drug increases from 10% to 20% skin permeation increases from 35.30 ± 0.79 µg/h/cm² to 53.74 ± 1.41 µg/h/cm². This was the effect due to the higher concentration gradient of the drug which may create reservoirs in the skin and from where permeate the drug. Flux was comparable for batches A3 and A4 Fig. 2 which were due to the saturation of the skin beyond the threshold concentration of the drug. Hence, 20% drug loading was found to be optimum. As shown in the results, it can also be inferred that as the drug concentration increases PSA concentration decreases and hence the peel strength of the patch also decreases.

TABLE 3: CHARACTERIZATION OF CLOZAPINE TRANSDERMAL PATCH WITH DIFFERENT DRUG LOADING

(mean ± SD, n=3)

Effect of Permeation Enhancer Type: Batches B1 to B5 were prepared by using 1, 8 – cineole, D-limonene, azone, IPM, and oleic acid respectively at a concentration of 10% w/w (of dry weight polymer) to achieve the target flux. The flux values of clozapine (µg/h/cm²) in the presence of the enhancers investigated and found to be highest for oleic acid viz. 90.84±1.48 µg/h/cm² (batch B5) and lowest for 1,8-cineole viz. 58.33 ± 1.21 µg/h/cm² (batch B1) Table 4. Permeation profiles are shown in Fig. 3.

TABLE 4: DETAILS OF DIFFERENT PERMEATION ENHANCERS USED FOR THE STUDY (mean ± SD, n=3)

The values of flux in the presence of permeation enhancers were found in following decreasing order: Oleic acid >IPM > Azone > D-limonene > 1, 8 Cineole. The above results were ascribed to the lipophilic character of the permeation enhancers ¹⁹. Oleic acid is a lipophilic fatty acid ²⁰ with the log P value of 7.7 ²¹. Hence, OA promotes the partitioning of clozapine into the acceptor phase. Moreover, OA acts by disrupting the lipid bilayer and hence increase the drug flux while IPM fluidizes the stratum corneum lipids and thereby enhancing flux ¹⁷. IPM Log p-value is 7.17 ²² while for azone log p-value is 6.2 ²³. Azones are non-interactive with the proteins; they get directly partitioned into the bilayer of lipid and by disrupting it they make the lipid layer more flexible 5.1,8-cineole disrupts the bilipid structure of subcutaneous layer ²⁴ while D-limonene extracts the lipid from subcutaneous layer and thereby enhance the penetration ²⁵. It was reported that the terpenes with higher polarity are more potent enhancers for hydrophilic drugs whereas non-polar terpenes are better enhancers for lipophilic drugs ²⁶. log p-value of 1,8-cineole was found to be 2.82 ± 0.25. On the contrary, D-limonene is a non-polar (hydrocarbon) terpene with a log p-value of 4.58 ± 0.23 ²⁷. So, based on the above findings OA was selected as the best suitable permeation enhancer for further studies and its effect on flux evaluated at different concentrations.

Effect of Permeation Enhancer Concentration: Permeation enhancer concentration plays a very important role in the permeation of the drug. Batches D1 to D3 were formulated by differing amounts of OA in range of 10%, 15% and 20% (of dry polymer weight) respectively. The flux value of clozapine (µg/h/cm²) for batch D1 was found to be 90.84 ± 1.48 µg/h/cm² while for batches D2 and D3 was found to be 109.59 ± 1.59 µg/h/cm² and 113.69 ± 1.74 µg/h/cm² respectively Table 5. The rate of permeation of the drug increased with increasing the concentration of OA, reaching a maximum of 20% Fig. 4. Permeation rate obtained with 15% and 20% concentration of OA was comparable and no noteworthy difference was found ²⁸. Hence formulation D2 was evaluated for further characterization.

TABLE 5: IMPACT OF CONCENTRATION OF OLEIC ACID (mean ± SD, n=3)

FIG. 4: EFFECT OF CONCENTRATION OF PERMEA-TION ENHANCERS ON EX-VIVO SKIN PERMEATION

Interaction Studies:

FTIR Studies: The FTIR spectra of pure clozapine demonstrated characteristic peaks at 3296.71 cm^-1 (N-H stretching), 2969.84 cm^-1 (C-H stretching), 1551.45 cm^-1 (C=N stretching), 1456.56 cm^-1 (Aromatic C=C Stretching), 822.49 cm^-1 (C-Cl stretching). Peaks of the FTIR spectra for physical mixture were detected at the same position as that of the drugs ²⁹.

In IR spectrum of Clozapine Fig. 5, the absorption at 3296.71 cm^-1 was assigned to the stretching vibration of N-H group which was red-shifted to the wave number of 3292.25 cm^-1 and 3291.16 cm^-1 for clozapine physical mixture and clozapine formulation ³⁰ and hence that red shift was attributed as a criterion for intermolecular hydrogen bonding ³¹.

DSC Studies: The thermogram of pure clozapine exerted a sharp endothermic peak at 188.59 ºC, corresponding to the melting point of clozapine Fig. 6. The major peak of clozapine disappeared from the DSC thermogram of optimized formulation, which was due to the homogenous dispersion of the drug in the PSA matrix ³².

FIG. 5: FTIR SPECTRA OF PURE DRUG, PSA, PHYSICAL MIXTURE, BLANK PATCH AND DRUG LOADED PATCH

FIG. 6: DSC CURVE FOR (A) PURE DRUG, (B) PHYSICAL MIXTURE OF DRUG AND PSA AND (C) CLOZAPINE TRANSDERMAL PATCH

Stability Study: This is necessary for the evaluation of transdermal patches during the storage. The results revealed no changes in the physical appearance of the formulation after six months. The % drug content was found to be 98.76 ± 0.37% after six months, while peel strength and flux were found 405 ± 3.15 cN/cm and 104.89 ± 1.43 µg/h/cm² respectively. The above results were insignificant (p > 0.05) when compared with the results of fresh patches Table 6. From the above findings, it was inferred that there was no drug crystallization observed even after six months.

TABLE 6: STABILITY STUDY FOR CLOZAPINE PATCH IN ACCELERATED CONDITION (mean ± SD, n=3)

CONCLUSION: Clozapine transdermal patch was formulated using pressure sensitive adhesives along with permeation enhancers to provide the sustained release of the drug with better permeation rate and hence the bioavailability as compared to the marketed formulation. Hence, the developed clozapine PSA patch proves to be a better alternative to conventional dosage forms and can be utilized in schizophrenics with improved patient compliance with reduced dosage frequency.

ACKNOWLEDGEMENT: We acknowledge that the funding of this research came from the self-financing of the authors and the authors are grateful to Amneal Pharmaceutical Pvt. Ltd., Ahmedabad for rendering generous support to carry out the research work. The authors are thankful to the Institute of Pharmacy, Nirma University, Ahmedabad, Gujarat, India for providing the necessary facilities to generate the manuscript that is a part of Doctor of Philosophy (Ph.D.) research work of Mr. Milan Agrawal to be submitted to Nirma University, Ahmedabad, India.

CONFLICTS OF INTEREST: The authors report no conflicts of interest.

REFERENCES:

1. Picchioni M and Murray R: Clinical review on schizophrenia. Psychiatry by Ten Teach 2017; 335: 102-13.
2. Schizophrenia Fact sheets details [Internet]. Geneva: World Health Organization; [updated Apr 2018; cited 2019 July 06]. Available from: https://www.who.int/news-room/fact-sheets/detail/schizophrenia
3. Manjunath K and Venkateswarlu V: Pharmacokinetics, tissue distribution and bioavailability of nitrendipine solid lipid nanoparticles after intravenous and intraduodenal administration. J Drug Target 2006; 14(9): 632-45.
4. Aggarwal G, Dhawan S and Kumar SLH: Formulation, in-vitro and in-vivo evaluation of transdermal patches containing risperidone. Drug Dev Ind Pharm 2013; 39(1): 39-50.
5. Liu C and Fang L: Drug in adhesive patch of zolmitriptan: formulation and in-vitro/in-vivo AAPS Pharm Sci Tech 2015; 16(6): 1245-53.
6. Parhi R and Suresh P: Formulation optimization and characterization of transdermal film of simvastatin by response surface methodology. Mater Sci Eng C 2016; 58: 331-41.
7. Sarkar G, Saha NR, Roy I, Bhattacharyya A, Bose M and Mishra R: Taro corms mucilage/HPMC based transdermal patch: An efficient device for delivery of diltiazem hydrochloride. Int J Biol Macromol 2014; 66: 158-65.
8. Imani M, Lahooti-fard F, Taghizadeh SM and Takrousta M: Effect of adhesive layer thickness and drug loading on estradiol crystallization in a transdermal drug delivery system 2010; 11(3): 1268-75.
9. Taghizadeh SM, Moghimi-Ardakani A and Mohamadnia F: A statistical experimental design approach to evaluate the influence of various penetration enhancers on transdermal drug delivery of buprenorphine. J Adv Res 2015; 6(2): 155-62.
10. Gowda DV, Gupta VK, Khan MS and Bathool A: Encapsulation of Clozapine into Beeswax Microspheres: Preparation, Characterization and Release Kinetics 2011; 3(4): 2199-207.
11. Mundargi RC, Patil SA, Agnihotri SA and Aminabhavi TM: Evaluation and controlled release characteristics of modified xanthan films for transdermal delivery of atenolol. Drug Dev Ind Pharm 2007; 33(1): 79-90.
12. Yang Z, Teng Y, Wang H and Hou H: Enhancement of skin permeation of bufalin by limonene via reservoir type transdermal patch: Formulation design and biopharmaceutical evaluation. Int J Pharm 2013; 447(1-2): 231-40.
13. Barot BS, Parejiya PB, Patel HK, Gohel MC and Shelat PK: Microemulsion-based gel of terbinafine for the treatment of onychomycosis: optimization of formulation using d-optimal design. AAPS Pharm Sci Tech 2012; 13(1): 184-92.
14. Gupta V, Singh S, Srivarstava M, Ahmad H, Pachauri SD and Khandelwal K: Effect of polydimethylsiloxane and ethylcellulose on in-vitro permeation of centchroman from its transdermal patches. Drug Deliv 2016; 23(1): 113-22.
15. Agency EM: European Medicines Agency (EMEA). Wiley Encycl Clin Trials 2008; (February): 1-20.
16. Banerjee S, Chattopadhyay P, Ghosh A, Bhattacharya SS, Kundu A and Veer V: Accelerated stability testing of a transdermal patch composed of eserine and pralidoxime chloride for prophylaxis against (±)-anatoxin a poisoning. J Food Drug Anal 2014; 22(2): 264-70.
17. Mutalik S, Parekh HS, Davies NM and Udupa N: A combined approach of chemical enhancers and sonophoresis for the transdermal delivery of tizanidine hydrochloride. Drug Deliv 2009; 16(2): 82-91.
18. S. Department of Health and Human. Guidance for Industry Starting Dose in Initial Clinical Trials Guidance for Industry Estimating the Maximum Safe. Pharmacol Toxicol 2005; (July): 1-27.
19. Rhee Y, Huh J, Park C, Nam T, Yoon K and Chi S: Conh 2007; 30(9): 1155-61.
20. Manley G: Public Access NIH Public Access 2013; 71(2): 233-6.
21. Jmol CC, Melting AD, Soluble I, Nfpa M and Baker JT: Oleic acid Oleic acid 2019; 1-4.
22. Isopropyl Myristate 110-27-0. Sax’s Danger Prop Ind Mater 2012; 1-53.
23. Properties P and Information M: Laurocapram 2019; 1-22.
24. Williams AC, Edwards HGM, Lawson EE and Barry BW: Molecular interactions between the penetration enhancer 1,8-cineole and human skin. J Raman Spectrosc 2006; 37(1-3): 361-6.
25. Zhao K and Singh J: Mechanism(s) of in-vitro percutaneous absorption enhancement of tamoxifen by enhancers. J Pharm Sci 2000; 89(6): 771-80.
26. Aqil M, Ahad A, Sultana Y and Ali A: Status of terpenes as skin penetration enhancers. Drug Discov Today 2007; 12(23-24): 1061-7.
27. El-Kattan AF, Asbill CS and Michniak BB: The effect of terpene enhancer lipophilicity on the percutaneous permeation of hydrocortisone formulated in HPMC gel systems. Int J Pharm 2000; 198(2): 179-89.
28. Moreira TS, de Sousa VP and Pierre MBR: Erratum to: A novel transdermal delivery system for the anti-inflammatory lumiracoxib: influence of oleic acid on in-vitro percutaneous absorption and in-vivo potential cutaneous irritation. AAPS Pharm Sci Tech 2010; 11(2): 719-19.
29. Sethia S and Squillante E: Solid dispersion of carbamazepine in PVP K30 by conventional solvent evaporation and supercritical methods. Int J Pharm 2004; 272(1-2): 1-10.
30. Liu N, Song W, Song T and Fang L: Design and eva-luation of a novel felbinac transdermal patch: combining ion-pair and chemical enhancer strategy. AAPS Pharm Sci Tech 2016; 17(2): 262-71.
31. Arunan E, Desiraju GR, Klein RA, Sadlej J, Scheiner S and Alkorta I: Defining the hydrogen bond: An account (IUPAC Technical Report). Pure Appl Chem 2011; 83(8): 1619-36.
32. Philip B, Singh H and Pathak K: Preparation, characterization and pharmacodynamic evaluation of fused dispersions of Simvastatin using PEO-PPO block copolymer. Iran J Pharm Res 2012; 11(2): 433-45.
    

    ---

    How to cite this article:

    Agrawal MB and Patel MM: Formulation and characterization of clozapine adhesive patches using various pressure sensitive adhesives and permeation enhancers. Int J Pharm Sci & Res 2021; 12(4): 2132-39. doi: 10.13040/IJPSR.0975-8232.12(4).2132-39.

    ---

    All © 2013 are reserved by the International Journal of Pharmaceutical Sciences and Research. This Journal licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 Unported License.

    ---