*3.2. Physicochemical Assessment of Methotrexate-Loaded Transdermal Patches*

All fabricated patch formulations of methotrexate were tested for physicochemical characterization. The results of various physicochemical tests revealed that all formulated patches were clear, smooth, transparent, flexible and nonsticky in appearance. The surface pH of all formulated patches (F1–F9) was found to be within the acceptable range, i.e., 5–5.9. Hence, skin irritation did not occur. Patch (F1–F9) thickness ranged between 0.50 and 0.60 nm, which showed uniform thickness. The weight ranged between 72.25 ± 0.08 and 78.67 ± 0.004 mg, which showed that the formulated patch weights were almost similar (Table 2). All formulated patches (F1–F9) passed the folding endurance test. The folding endurance of all formulated patches was more than the predefined range of folding endurance, i.e., ≥30. Hence, all formulated patches proved to be the best and acceptable dosage forms used transdermally. However, there was an increase in moisture content with an increase in hydrophilic polymers. This may be due to the higher affinity of water for hydrophilic polymers than hydrophobic polymers. The percent moisture uptake was found to be higher in the patch containing EC because it absorbs moisture. The low moisture content in the prepared formulations helped them to remain stable and free from being completely dry and brittle patches. The moisture loss ranged from 6.8 ± 0.38 to 8.28 ± 0.85. Similarly, the moisture absorption observed was found to be satisfactory and ranged from 8.45 ± 1.22 to 12.79 ± 1.46. The tensile strength and elongation values of the formulated patches ranged between 9.36 kg/cm<sup>2</sup> and 12.75 kg/cm2, and proper flexibility was observed, as indicated by the high values. All formulated patches showed uniformity in drug content that was quite good and ranged between 97.42% and 99.13%. The results of this study show that the formulated patches could produce transdermal matrix-type patches with uniform drug contents. The plasticizer used was PEG-400 to reduce the brittleness of the patches. The current study indicates that the addition of PEG-400 at 25% *w/w* of polymers produces uniform, flexible and smooth patches. Patches formulated with the addition of PEG-400 as plasticizer were found to be best for tensile strength and folding endurance properties.

**Figure 1.** ATR–FTIR spectra: (**a**) MTX; (**b**) F1; (**c**) F2; (**d**) F3; (**e**) F4; (**f**) F5; (**g**) F6; (**h**) F7; (**i**) F8; (**j**) F9.


**Table 2.** Characterization of MTX-loaded transdermal patches (F1–F9). Data were expressed as mean ± SD, *n* = 3.

#### *3.3. Stability Studies*

Stability studies of all formulated patches are shown in Table 3. All formulated patches showed almost similar drug content data, as observed at the beginning of the study. All formulated patches showed acceptable, flexible and elasticity properties at the beginning Figure 2a, and end of this study in Figure 2b, thus ensuring the stability of the formulated patches.

**Table 3.** Stability studies of MTX-loaded transdermal patches (F1–F9), Data were expressed as mean ± SD, *n* = 3. Significant compared to formalin (*p* < 0.05).


#### *3.4. Skin Irritation Study*

The skin irritation study revealed that no irritation erythema or edema occurred. During the study period and after the removal of transdermal patches, no edema or erythema was found, which indicates that the formulations were nonirritant, while formalin (standard irritant) produced severe erythema and edema. The Draize test was negative, indicating that no skin irritation occurred if the score of the tests was less than 2 showed in Table 4.

**Figure 2.** Physical appearance of formulated (F1–F9) patches shown at Day 1 (**a**) and after 180 days (**b**).


