Transdermal Patches in Medicine

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