Permeation enhancers improve skin permeability, facilitating drug delivery through the stratum corneum.
Selection depends on the drug, formulation, and desired absorption rate.
Chemical Enhancers
Compounds that reduce the skin's barrier function by interacting with stratum corneum lipids and proteins.
Mechanisms of Action
Lipid Interaction: Extracting or fluidizing skin lipids.
Protein Modification: Altering keratin structure.
Drug Solubility: Increasing solubility and partitioning.
Examples
Solvents: Ethanol, propylene glycol (lipid extraction).
Surfactants: Sodium lauryl sulfate, cetyl alcohol (lipid interaction).
Fatty Acids: Oleic acid, linoleic acid (lipid disruption).
Terpenes: Menthol, limonene (solubility enhancement).
Physicochemical Enhancers
Use physical forces or devices to enhance drug delivery.
Examples
Iontophoresis: Electric current drives charged drugs into the skin.
Sonophoresis: Ultrasound waves improve permeability.
Microneedles: Create microchannels in the skin for easier drug passage.
Electroporation: Short electric pulses form transient aqueous pores.
Magnetophoresis: Magnetic fields enhance drug permeation.
Ideal Properties of Permeation Enhancers
Safety: Non-toxic, non-irritating.
Reversible Action: Temporary barrier disruption.
Low Concentration: Effective in small amounts.
Non-Reactive: Stable with drugs and formulation components.
Improves Solubility and Stability: Enhances drug compatibility.
Rapid Onset: Quick action post-application.
Sustained Effect: Duration aligns with drug delivery needs.
Key Considerations
Selecting a permeation enhancer requires understanding:
Drug Properties: Solubility, stability, lipophilicity.
Mechanisms of Action: Enhancer’s interaction with the skin.
Safety and Efficacy: Verified through rigorous trials.
Optimal enhancer selection ensures effective, safe, and efficient drug delivery in TDDS