Effect of Fluid Paraffin on the Formulation Properties of Pressure Sensitive Adhesive Formulations Containing Diclofenac Sodium

Understanding the relationship between the release characteristics of the active ingredient in the tape formulation and the pharmaceutical characteristics of the adhesive layer can optimize therapeutic efficacy and improve patient adherence. This study aimed to clarify the effect of liquid paraffine (LP)/styrene-isoprene-styrene (SIS) triblock copolymer ratio on pressure-sensitive adhesive (PSA) formulation properties, such as adhesive properties and drug release, with a certain amount of diclofenac sodium (DFS) and tackifier. The effects of changes in PSA composition in DFS-containing tape formulations on adhesive and drug release properties were evaluated. The viscoelasticity results showed rigid gel-like behavior at low angular frequencies regardless of the LP/SIS ratio, and deformable gel-like behavior at high angular frequencies, with a maximum plasticizing effect of LP up to an LP/SIS ratio of 3.7. The peel adhesion test results showed that peel adhesion was not affected, but indicated a decreasing trend by increasing the LP/SIS ratio in the presence of DFS. Drug release test results showed that DFS release increased up to 24 h for LP/SIS ratios of up to 3.7, but decreased when the LP/SIS ratio was 6. The results of the drug permeation tests were similar to those of the drug release tests. In conclusion, it is possible to change the drug release properties by changing the amount of LP in the tape formulation; however, no definitive correlation was found between the adhesive and drug release properties.