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5. Pressure sensitive adhesives (PSAs)
• PSAs are the material that adhere to a substrate, in this case skin, by application of light

force and leave no residue when removed
• It is a crucial component of all transdermal delivery patches , as it ensures an intimate

contact between the patch and the skin.
• The adhesives and their adhesion property are vital for the quality and efficacy of the

patch. Improper adhesion leads to reduction of contact surface area (patch falls off), that
eventually resulted in incorrect dosing of patients.
• The PSA can be located around the edge of the TDDS or be laminated as a continuous
adhesive layer on the TDDS surface.

• Commonly used Pressure-sensitive adhesives are polyacrylates, polyisobutylene or
polysiloxane. What about natural adhesives??

Ideal characters

▪ The excellent adhesive should be a biocompatible, nonirritant, and non-sensitizing
polymer.

▪ It should be water and humidity resistant and should form good adhesive bonds
irrespective of skin structure like oily or wrinkled skin.

▪ It should establish and maintain bonds with the skin for an intended period and can easily
be removed from skin without retaining any residues or causing any skin damage.

▪ It should permit unimpeded drug flux to the skin and be compatible with all other system
components.

6. Release liner

• It is the component of the patch, which is in intimate contact with the adhesive layer
during storage and transportation

• It is peeled off and discarded immediately before the application.

• It prevents loss of drug in the adhesive layer during storage and protects product against
contamination.

• The release liner is fabricated from non-occlusive (paper fabric) or occlusive
(polyethylene) material, and usually coated with silicon or teflon (why?)

7. Other excipients

Plasticizers and solvents

▪ Various solvents such as chloroform, methanol, acetone, isopropanol and
dicholoromethane are used to prepare drug reservoir.

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