Formulation and Evaluation Chlorzoxazone Transdermal Patches

Amol R. Kharat¹, Savita B. Nikam², Priya Mijgar³

¹Associate Professor, Government College of Pharmacy, Amravati, Maharashtra, India.

²M. Pharmacy, Government College of Pharmacy, Chhatrapati Sambhajinagar, Maharashtra, India.

³M. Pharmacy, Government College of Pharmacy, Chhatrapati Sambhajinagar, Maharashtra, India.

*Corresponding Author E-mail: savitanikam10@gmail.com

ABSTRACT:

The present research aims to develop and evaluate chlorzoxazone-loaded transdermal patches for the effective management of muscle spasms. These patches serve as an alternative to conventional oral dosage forms, which are often linked to systemic adverse effects. Chlorzoxazone, a centrally acting skeletal muscle relaxant, is widely prescribed to alleviate muscle pain and stiffness. However, oral administration frequently results in gastrointestinal irritation and inconsistent plasma drug concentrations. Transdermal drug delivery systems offer a promising approach by enabling sustained drug release and reducing systemic toxicity. In this study, different polymer combinations were utilized to optimize drug release and enhance skin permeability. The patches were fabricated using the solvent evaporation method, with varying concentrations of chlorzoxazone, polymers, plasticizers, and penetration enhancers. The prepared patches were evaluated for their mechanical and physicochemical properties, including thickness, weight uniformity, drug content, and in vitro release profile. Results indicated uniformity in thickness, weight, and drug loading, ensuring dose consistency. In vitro diffusion studies demonstrated a sustained release of chlorzoxazone for up to 12 hours. Overall, the developed chlorzoxazone transdermal patches represent a potential substitute for oral therapy, providing prolonged drug delivery and improved patient compliance.

KEYWORDS: Chlorzoxazone, Transdermal patches, Muscle relaxant, Drug delivery system, Skin permeation, Sustained release.

INTRODUCTION: 

Transdermal Drug Delivery Systems (TDDS) have emerged as an advanced and patient-friendly alternative to traditional oral and injectable drug administration methods¹. They enable the continuous and controlled release of therapeutic agents through the skin directly into the bloodstream. This route bypasses gastrointestinal degradation and first-pass hepatic metabolism, thereby minimizing gastrointestinal irritation and improving drug bioavailability.

Additionally, transdermal patches help maintain consistent plasma concentrations of the drug, reducing the fluctuations in drug levels that are often observed with oral dosing².

As part of modern Novel Drug Delivery Systems (NDDS), TDDS have gained considerable research interest in recent years due to their capacity to provide sustained and targeted drug delivery through the skin. A transdermal patch is a flexible, multilayered dosage form designed to adhere to unbroken skin and deliver one or more drugs in a controlled manner³. The drug is generally released by diffusion, ensuring a steady rate of absorption into systemic circulation over a prolonged period⁴.

The design and optimization of TDDS require a multidisciplinary approach that begins with the selection of a suitable drug molecule. The formulation must demonstrate adequate skin permeability in in vivo and ex vivo studies, as well as stability, patient comfort, and scalability for large-scale production. An ideal transdermal formulation should balance the physicochemical characteristics of the drug, aesthetic acceptability for users, and economic feasibility for manufacturers⁵.

Although transdermal formulations are relatively more costly than conventional dosage forms, their distinct advantages have made them increasingly popular⁶. They offer painless administration, ease of use, predictable absorption, reduced side effects, consistent plasma levels, and improved patient compliance. Moreover, therapy can be terminated instantly by simply removing the patch from the skin⁷.

Chlorzoxazone is a centrally acting skeletal muscle relaxant commonly prescribed for the management of painful muscle spasms⁸. While effective when taken orally, it often causes gastrointestinal discomfort and variable plasma concentrations due to metabolic degradation. To overcome these drawbacks and ensure consistent therapeutic action, transdermal drug delivery presents a promising alternative for chlorzoxazone administration ^9,10.

MATERIALS AND METHODS:

Materials:

Chlorzoxazone:

The drug Chlorzoxazone was kindly provided as a gift sample by Alican Pharmaceuticals Pvt. Ltd., India. Sarigam, District Valsad, Gujrat., HPMC K100M chem Products, Ethyl cellulose chem. Products, Glycerine, Methanol, Chloroform,

Preformulation study:

Melting point:

The melting point of Chlorzoxazone was determined using a melting point apparatus, and it was found to be approximately 190°C.

Infrared spectroscopy:

The infrared spectral analysis of Chlorzoxazone was carried out using an FT-IR spectrophotometer (S). The sample was scanned over a wavelength range of 400–4000 cm⁻¹ to identify characteristic functional groups. For sample preparation, Chlorzoxazone was mixed thoroughly with potassium bromide (KBr) and compressed into a transparent disc using a hydraulic press at a pressure of five tonnes for five minutes. The prepared KBr pellet was then placed in the optical path of the instrument, and the resulting FT-IR spectrum was recorded¹¹.

UV Spectrophotometer:

The UV absorption spectrum of Chlorzoxazone was recorded using a UV–Visible spectrophotometer. A solution of the drug was prepared in 0.1 N NaOH, and the spectrum was scanned in the UV range. The wavelength of maximum absorption (λmax) was observed at 243 nm.

Calibration Curve of Chlorzoxazone: Preparation of standard stock solution: 

A quantity of 10 mg of Chlorzoxazone was accurately weighed and transferred into a 100 mL volumetric flask, and the volume was made up with 0.1 N NaOH to prepare the stock solution. From this stock, serial dilutions were performed to obtain solutions with concentrations of 2, 4, 5, 6, 8, and 10 µg/mL. The standard calibration curve was constructed by measuring the absorbance of these solutions at 243 nm using a UV–Visible spectrophotometer and plotting absorbance against concentration.

Formulation development:

Following critical formulation parameters were identified

1) Polymer ratio (HPMC: EC)

2) Solvent ratio (CHL: MeOH)

3) Plasticizer amount (GLY)

Method for preparation of transdermal patches:

Drug and polymer weighing: Using an analytical balance that had been previously calibrated, drugs and polymers were precisely weighed on aluminium foil.

Making the solvent mixture: The two organic solvents were precisely measured and combined in a beaker. Different ratios of CHL and MeOH were used to create the mixture.

Preparation of polymeric solution: Accurately weighed amounts of both polymers (Total 1000mg) were dissolved in sufficient solvent mixture, in separate beakers. Addition of polymers to solvent mixture was done slowly with continuous stirring to avoid formation of lumps. The solution of EC was less viscous as that of HPMC. Hence solution of EC was added to solution of HPMC with continuous stirring using less rod. Stirring was continued till a homogeneous clear mass was resulted.

Table No.1: Formulation for transdermal patches

	Excipient	f1	f2	f3	f4	f5	f6
1	Polymer ratio (HPMC: EC)	160:200	210:100	320:280	460:540	640:360	870:130
2	Solvent ration (CHL: MeOH)	10:10	10:15	15:10	15:15	10:20	7.5:22.5
3	Plasticizer amount (GLY)	1	1	1	1	1	1
4	Drug	100mg	100mg	100mg	100mg	100mg	100mg

Drug and polymer weighing: Using an analytical balance that had been previously calibrated, drugs and polymers were precisely weighed on aluminium foil. making the solvent mixture: The two organic solvents were precisely measured and combined in a beaker. Different ratios of CHL and MeOH were used to create the mixture. The medication and polymers were dissolved using this solvent mixture.

Making the polymeric solution: In separate beakers, precisely weighed quantities of each polymer (a total of 1000 mg) were dissolved in an adequate solvent mixture. To prevent lump formation, the polymers were added to the solvent mixture gradually while being stirred continuously. Compared to HPMC's solution, ECs was less viscous. Thus, using a glass rod, the EC solution was continuously stirred in to the HPMC solution. Stirring persisted until.

Patch casting: The resulting mixture was transferred onto a petri plate. Care was taken when pouring to ensure that the mass's thickness remained constant. We let this mass to expand in to the petri dish. he prepared patches were allowed to dry at room temperature for 24 hours. An inverted funnel was positioned over the Petri dish to ensure uniform and controlled evaporation of the solvent. After complete solvent removal, the patches were carefully detached from the dish and cut into uniformly sized squares for further evaluation^13to20.

Fig. no. 1: Transdermal patches

Storage:

The dry patches were kept in to self-sealing polythene bags, placing a piece of butter paper between two patches. These bags were stored n desiccators until use.

Fig. 2: Transdermal patches casted on petri dish

Characterization of Transdermal Patches: Transdermal patches are designed to deliver a controlled, lower dose of a drug over a specified period, with the aim of enhancing patient compliance and improving therapeutic outcomes. To ensure consistent performance and reproducibility under defined conditions, evaluation studies are essential. These investigations, which can be classified into several categories, help predict the effectiveness and reliability of transdermal patch formulations²¹.

1) Physicochemical evaluation

2) In vitro evaluation

Physicochemical evaluation:

Drug content determination:

A 50 mL beaker was filled with 3 mL of MeOH after a 50 mg quantity of the patch was precisely weighed. To make sure the patch piece was completely submerged in the solvent, t was gently shaken. This underwent a two-minute sonication. Following sonication, a precise 1 mL volume of the resulting solution was removed using a micropipette and placed in to a 5 mL volumetric flask²². MeOH It was used to obtain the amount up to 5 mL. The percentage of medicine content was then given after the drug's amount was assessed using the UV spectrophotometer technique at 264 nm.

Thickness:

Using a screw gauge, the transdermal patch's thickness was ascertained. Five distinct places on the patch were used to measure its thickness: four n the corners and one in the centre. The thickness ± SD n millimetres was obtained by averaging these five values²³.

Uniformity of weight:

Ten selected patches at random were weighed independently, and the mean weight was determined n order to examine any weight fluctuation n the prepared patches. There shouldn't be a big difference between the average weight and the individual weight. Greater homogeneity s achieved with less variance²⁴.

Folding endurance:

Folding endurance refers to the number of times a patch can be folded at the same point without breaking. This test was performed to evaluate the flexibility and mechanical strength of the transdermal patch. A specific section of the patch was repeatedly folded at the same location until it fractured, and the folding endurance was recorded as the total number of folds required to cause breakage²⁵.

Flatness:

A section was removed from the middle. of the patch, and two were cut from each side to assess the patch's level of flatness. Every strip's length was measured and any variations were noted. The percentage of constriction was calculated using this data, and the results were displayed as a percentage of flatness. 100% flatness s indicated by 0% constriction²⁶.

It’s calculated from following formula:

                              L₁ – L₂

% Constriction = ------------- × 100

                                 L₁

Where L₁= Initial length of strip (cm)

L₂= Final length of strip (cm)

Percentage of moisture content:

One patch (W1 mg) was precisely weighed from each batch for this test. For a whole day, these weighed patches were kept n a desiccator at the surrounding temperature that contained calcium chloride. Patches were weighed again after the allotted time until a consistent weight (W2 mg) was achieved^27,28.

The present moisture content was calculated using following formula:

                                     W₁ – W₂

% Moisture content =  ------------- × 100

                                           W₁

In vitro evaluation:

In vitro dissolution studies:

Using a paddle over a disc Speciality type 4 apparatus was used for the transdermal patches n vitro dissolution study. The drug's ejection from the already prepared patches. Dried strips that have been determined width s to be cut into specified shape, weighed, and attached on a glass plate using an adhesive. After equilibrating the apparatus to 32±0.5°C, the glass plate was submerged n 500 mL of the phosphate buffer (pH 7.4) or dissolving medium. Next, the paddle was moved at a pace of 50 revolutions per minute and positioned 2.5 cm apart from the glass plate. Samples (5-mL aliquots) may be removed up to 24 hours apart at the proper times. and the samples were filtered, and at 243nm, they were examined. using a UV spectrophotometer. Three replicates of the experiment must be carried out so that the mean value may be determined²⁹.

RESULT:

Preformulation Study (Selection of SNEDDS Components) Preformulation study

Melting point:

Melting point observed n the range of 190-191°C by using capillary method.

Table no.2: Determination of Meting point

Parameter	Observed value	Reference value	Inference
Melting Point	190-191° C	191° C	Complies with the standard

UV visible Spectrum of Chlorzoxazone:

The UV spectrum of Chlorzoxazone in 0.1 N NaOH was recorded using a UV–Visible spectrophotometer. The wavelength of maximum absorption (λmax) was observed at 243 nm.

Figure:3 UV Visible Spectrum of Chlorzoxazone at λ ma xi243

Table no. 3: Visible Spectrum of Chlorzoxazone:

	Observed value	Standard value
Spectrum (lambda max.)	243 nm	244 Nm

Calibration Curve of Chlorzoxazone:

Preparation of standard stock solution: 

A precisely weighed 10 mg of Chlorzoxazone was transferred into a 100 mL volumetric flask, and the volume was made up with 0.1 N NaOH to prepare the stock solution. This stock solution was further diluted to obtain concentrations of 2, 4, 5, 6, 8, and 10 µg/mL. The absorbance of each solution was measured at 243 nm using a UV–Visible spectrophotometer, and a standard calibration curve was constructed by plotting absorbance against concentration^30,31.    

Fig. no.4: Standard curve for Chlorzoxazone

Infrared spectroscopy:

The FT-IR spectrophotometer (S) was used to conduct an IR spectroscopy analysis of chlorzoxazone. A 400 cm-1 wavelength range was covered by the spectra scan. The process involved spreading a sample of KBr and compressing t onto the disc using a hydraulic press30 that was set to apply pressure of five tonnes for five minutes. After the pellets were positioned in the optical path, the FT-IR spectra were acquired ^32,33.

Figure no. 5: FT-IR spectrophotometer

Table no: 4 IR Observation peak wave no.

Sr. no.	Observed peak at wave no.	Groups
1	1693	C=O	Amid linkage
2	3471	NH	Amid group
3	1622	−COOH	Carboxyl acid
4	709		Mon substituted benzene
5	416	Cl	Chlorine

Evaluation tests:

Drug content determination

The percentage of drugs of prepared patches s shown n following table.

Table No.5: % Drug content of transdermal patches

Sr. No.	Formulatio ncode	% Drug Content*
1	f1	80.70 ±0.7
2	f2	90.40 ±0.9
3	f3	95.03 ±0.9
4	f4	96.70 ±0.4
5	f5	95.90 ±0.4
6	f6	97.06 ±0.7

Thickness:

The average thickness of transdermal patches s shown n following table.

Table No.6: Average thickness of transdermal patches

Sr. No.	Formulation code	Average Thickness* (mm)
1	f1	0.11±0.078
2	f2	0.09 ±0.045
3	f3	0.12 ±0.007
4	f4	0.10 ±0.008
5	f5	0.07 ±0.005
6	f6	0.08 ±0.007

Uniformity of weight:

The mean weight of the prepared transdermal patches is presented in the following table.

Table No. 7: Uniformity of weight of transdermal patches

Sr. No.	Formulation code	Average weight* (mg)
1	f1	147.0 ±8.5
2	f2	110.5 ±4.0
3	f3	280.3 ±5.7
4	f4	187.0 ±9.5
5	f5	150.5 ±6.4
6	f6	250.3 ±9.0

Folding endurance:

The quantity of folds necessary for the patch to break is shown in following table, with respective batches.

Table No. 8: Folding endurance of transdermal patches

Sr. No.	Formulation code	Folding endurance*
1	f1	56 ±6
2	f2	35 ±10
3	f3	89 ±40
4	f4	43 ±2
5	f5	55 ±3
6	f6	59 ±4

Flatness:

% Constriction with respective % flatness of patches is shown n table below.

Table No. 9: Flatness of transdermal patches

Formulation code	L1 (cm)	L2 (cm)	% Constriction	% Flatness
f1	1.0	1.0	0	100
f2	1.0	1.0	0	100
f3	1.0	1.0	0	100
f4	1.0	1.0	0	100
f5	1.0	1.0	0	100
f6	1.0	1.0	0	100

Percentage of moisture content:

The weight lost by patches due to loss of moisture s shown in following table.

Table No. 10: Moisture content of transdermal patches

Sr. No.	Formulation code	% Weight loss*
1	f1	3.0 ±0.2
2	f2	0.9 ±0.6
3	f3	1.3 ±0.7
4	f4	1.1 ±0.4
5	f5	0.8 ±0.3
6	f6	2.0 ±0.2

Percentage of moisture uptake:

The weight gain of patches due to exposure to moisture is shown in following table.

Table No. 11: Moisture uptake by transdermal patches

Sr. No.	Formulation code	% Weight gain*
1	f1	1.1 ±0.0
2	f2	3.0 ±0.9
3	f3	3.5 ±0.2
4	f4	1.1 ±0.4
5	f5	1.6 ±0.3
6	f6	3.5 ±0.2

In vitro dissolution studies:

Table No. 12 Shows % drug release for all batches and Fig No: 06 and o7 show the release pattern for each batch.

Table No. 12: % Release of Chlorzoxazoneipatche

Sr. No.	Formulation code	% Cumulative release
1	f1	60.59
2	f2	80.96
3	f3	84.46
4	f4	88.31
5	f5	90.00
6	f6	92.04

Fig.no.06: Show the release pattern of Chlorzoxazone from patch batch F1, F2 and F3  in vitro dissolution studies.

Fig. no. 07: Show the release pattern of Chlorzoxazone from patch batch F4 , F5 and F6 in vitro dissolution studies.

CONCLUSION:

Transdermal patches for chlorzoxazone represent a promising alternative to oral administration, offering the potential for sustained drug release, improved bioavailability, and reduced gastrointestinal side effects. By avoiding the liver's first-pass metabolism, transdermal delivery could provide more consistent plasma concentrations, enhance therapeutic efficacy while minimize systemic adverse effects. Nine batches were studied in vitro for dissolution; batches f1, f2, and f3 totally dissolved in eight hours. so, these batches were rejected at 12 hours, the f4, f5 and f6 batches among the others had entirely decomposed. The batch F6 had the best performance, with a percentage cumulative medication release of 92.04% at 12 hours.

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Received on 16.10.2024      Revised on 11.04.2025

Accepted on 17.07.2025   Published on 13.01.2026

Available online from January 17, 2026

Research J. Pharmacy and Technology. 2026;19(1):289-295.

DOI: 10.52711/0974-360X.2026.00041

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