Iontophoresis is a non-invasive method of delivering drugs into the body. With a low-level electrical current, iontophoresis repels drug ions through the skin and into underlying tissue.
The use of iontophoresis for transdermal drug delivery has been successfully used by medical professionals for decades and continues to increase dramatically because of its advantages.
Advantages of Iontophoresis
- Virtually painless when properly applied
- Provides option for patients reluctant or unable to receive injections
- Reduced risk of infection due to non-invasive nature
- Medications delivered directly to the treatment site
- Minimizes potential for tissue trauma from an injection
- Treatments are completed in minutes
Mechanism of Iontophoresis
Passive transdermal administration of drugs, as with a skin patch, is suitable for non-ionized drugs requiring a relatively small dosage. Ionized drugs, however, do not easily penetrate the skin and are therefore not generally suitable for routine transdermal dosage.
An external energy source in the form of an applied direct electrical current will increase the rate of penetration by assisting the movement of ions, driving the drug across the skin. Like charges repel each other and opposite charges attract. Thus, positive ions in a water-soluble medication are repelled from a positively charged electrode positioned over the tissue into which the medication ions are to be delivered, and negative drug ions are repelled from a negatively charged electrode. The direct current moves the ions from the drug electrode through the patient’s skin.
During iontophoresis, a shift in pH occurs due to hydrolysis of water. The competing ions may result in a less efficient drug transfer. Buffers may be built into the electrode to minimize this effect, but the buffer materials should be bound or immobile so they do not compete with the active drug.
Products that use chemical buffers added to the electrode reservoir are undesirable as these introduce a high concentration of extraneous mobile ions. The buffer ions then compete with the drug ions for current and reduce the overall delivery efficiency of the system.
Four components needed for effective iontophoresis delivery:
- Power source for generating controlled direct current
- Electrodes that contain and disperse the drug
- Negatively or positively charged aqueous medication of relatively small molecule size (<8000 Daltons)
- Localized treatment site