Transdermal Patches in Medicine

Study Notes

Transdermal Patches

A medicated adhesive patch that delivers a specific dose of medication through the skin and into the bloodstream.
Used in various therapeutic areas, including pain management and smoking cessation.

Advantages of Transdermal Patches

Suitable for unconscious patients
Improves patient compliance
Easy to discontinue in case of toxic effects
Decreases side effects
Decreases the dose of the drug
Provides controlled release of the drug
Painless medication delivery
Delivers the drug mainly to the skin
No GI distress or other physiological contraindications
Allows administration of drugs with narrow windows
Easy to use and non-invasive therapy
Avoids the first-pass metabolism
Avoids hazardous waste if used in place of injections

Disadvantages of Transdermal Patches

Cannot deliver drugs that require high blood levels
Inconvenient for drugs that require large doses
Cannot deliver large-molecular size drugs
Adhesive may not adhere well to all types of skin
Drug formulation may cause skin irritation
Patches can be uncomfortable to wear
Drug must have desirable physicochemical properties to penetrate the stratum corneum
The barrier function of the skin changes from one site to another, from person to person, and with age

Components of Transdermal Patches

Liner: a protective layer that prevents loss of drug and contamination
Drug: should have non-ionic, low molecular weight, adequate solubility, low melting point, and potent properties
Permeation enhancers: promote skin permeability, work rapidly, and have no pharmacological activity
Polymer matrix: controls the release of the drug, should be stable, non-reactive, and easy to manufacture
Adhesive: provides good adherence, should not irritate or sensitize the skin, and should be easily removable
Rate controlling membrane: limits the flow of the drug from the reservoir and matrix system
Backing layer: provides a flexible and impermeable layer that prevents drug from leaving the dosage form
Packing: critical for the stability and integrity of the product, should be impermeable to water vapor

Examples of Drugs Used as Transdermal Patches

Nicotine patch: releases nicotine in controlled doses to help with cessation of tobacco smoking
Fentanyl and Buprenorphine patches: provide round-the-clock relief for severe pain
Estrogen patches: treat menopausal symptoms and post-menopausal osteoporosis
Contraceptive patch: delivers hormones for birth control

Types of Transdermal Patches

Membrane permeation controlled: drug reservoir is encapsulated in a rate controlling membrane
Adhesive diffusion controlled: drug reservoir is formulated with an adhesive polymer
Matrix diffusion controlled: drug is dispersed in a liquid polymer or highly viscous base polymer
Microreservior dissolution controlled: a combination of reservoir and matrix system

Evaluation of Adhesion Properties

Peel adhesion properties: measure the force required to remove an adhesive coating from a test substrate
Tack adhesion properties: measure the ability of a polymer to adhere to a substrate with little contact pressure
Tests for tack determination: thumb tack test and rolling ball tack test

Description

Learn about transdermal patches, a medicated adhesive patch used to deliver a specific dose of medication through the skin and into the bloodstream. Understand different components and types of transdermal patches.