Permeation enhancers are substances that facilitate the transport of drugs or other compounds across biological membranes, particularly the skin or the intestinal barrier. They are often used in pharmaceutical formulations to improve the absorption and bioavailability of active ingredients. Here are some key points about permeation enhancers: 


Types of Permeation Enhancers

  1. Chemical Enhancers:

    • Surfactants: Reduce surface tension and disrupt lipid layers in membranes (e.g., sodium lauryl sulfate).
    • Solvents: Improve solubility and disrupt skin barriers (e.g., ethanol, propylene glycol).
    • Chelating Agents: Bind to metal ions and alter membrane properties (e.g., EDTA).
    • Penetration Enhancers: Compounds like fatty acids or esters that alter lipid structure (e.g., oleic acid, isopropyl myristate).

  2. Physical Enhancers:

    • Iontophoresis: Uses electrical current to drive charged drugs through the skin.
    • Sonophoresis: Uses ultrasound to enhance drug permeation.
    • Microneedles: Tiny needles create microchannels in the skin to facilitate drug delivery.

  3. Biological Enhancers:

    • Enzymes: Can modify the drug or enhance permeation through enzymatic action.

Mechanisms of Action

  • Disruption of Lipid Bilayers: Many enhancers modify the lipid structure of the skin or intestinal membranes, creating transient pores.
  • Increase in Drug Solubility: Enhancers can increase the solubility of drugs, making it easier for them to cross barriers.
  • Reduction of Viscoelasticity: Some enhancers can alter the mechanical properties of biological membranes, facilitating drug movement.

Applications

  • Transdermal Drug Delivery: Enhancers are crucial for patches and topical formulations.
  • Oral Drug Delivery: They can improve the absorption of drugs in the gastrointestinal tract.
  • Vaccine Delivery: Some permeation enhancers are used to enhance vaccine efficacy.

Considerations

  • Safety: Enhancers must be safe for human use and not cause irritation or adverse reactions.
  • Effectiveness: The choice of enhancer depends on the drug's properties and the desired route of administration.

In summary, permeation enhancers play a vital role in improving drug delivery systems by modifying biological barriers and enhancing the absorption of therapeutic agents.