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Iontophoresis—an overview

Definition

Iontophoresis is the process by which drugs, usually dexamethasone and lidocaine, are introduced into a joint or small body part via electrical current. It is non-invasive, painless and it eliminates potential side effects and adverse reactions which can occur with medications delivered orally or by injection.

Clinical trivia: ionto provides more local concentrations than medications taken by mouth, but less than injected medications.

Basic process

·Like electrical charges repel each other; current is used to repel like electrically charged ions (medication) to penetrate skin and underlying soft tissues.

· Dc generator (id3) provides an electrically charged field for medication movement into tissues.

· Dexamethasone carries a negative charge when dissolved in a solution so it will always be applied with a negative polarity.

· Medication is delivered to local area via active (delivery) electrode and current returns to unit via dispersive (return) electrode.

3 basic components

1. id3 (Dc generator) provides direct current

• Typically treatment time: 4mA over 10 minutes or 40mA
• Contols and regulates treatment peramiters wich includes time dosage and mA (currant)

2. Active (delivery electrode)

• 3 layers
• Fiber reservoir pad: absorbs solution to be delivered
• Polyester coated w/ silver/silver chloride: provides ph balanced current evenly across the reservoir
• Soft, flexible foam coated with a medical grade adhesive

3. Dispersive (return electrode)

• 3 layers
• Self-adhering buffered conductive gel:
• Conductive (carbon) film: evenly distributes current across the electrode
• White non-conductive vinyl-like material
   

Facts about iontophoresis

Adhesion is the most important factor; better contact equals better conduction/maximum drug delivery with least chance for burns/hot spots.

· All manufacturers use buffering gels on the return electrodes.

· Some Manufacturers use buffering agents on delivery electrodes when carbon film is used in place of silver/silver chloride (carbon film does not provide a stabile conductive environment).

· In orthopedic rehab, 99.9% therapy is to deliver dexamethasone (anti-inflammatory drug).

· Current used: direct (galvanic) current only; provides uni-directional electrostatically charged field from active to return electrode.

· Since dexamethasone is typically used in orthopedic rehab we will assume all statements regarding ionto relate to this medication.

Important note regarding electrophysiology at both electrode sites

Even in the absence of medication, an alkaline reaction occurs at the cathode due to the formation of sodium hydroxide while an acidic reaction occurs at the anode due to formation of hydrochloric acid.

Important for pad properties to have a stabilizing mechanism in place to prevent this shift (acidic and basic ph shifts can cause burns). Silver/silver chloride provides this aditional stabilization.