Iontophoresis Flashcards
What is Iontophoresis
Use of low voltage direct current to move charged ions across a dermal barrier.
Biophysical Mechanism
- Primary route for ion transport through sweat glands, the pores of the skin or hair follicles.
- Assumption that the current “drove ions through the skin” is probably not correct.
- Current thought: Better to think of as facilitating absorption
Facilitating Absorption
- Electroporation- increase in number of pathways in skin for drug delivery.
- Epidermal cells’ lipid dipole layer has a negative charge.
- When current applied, cells rearrange to open pathways.
- This takes 3-4 minutes of current application.
Drugs can be delivered by iontophoresis if:
- Can be ionized
- Are stable in solution
- Not altered by electrical current
- Molecules are small in size
What would you place under (+)?
(+)
Same with negative
An electrode containing drug is called…
“treatment”, “active” or “delivery”
Opposite electrode is called…
“return” or “dispersive”
Depth of Delivery of Drug
- Reports vary by study ranging from a depth of 1 to 3 mm.
- Over 12-24 hours the drug diffuses more deeply (up to 17 m or 2/3 inch)
- There is also some evidence that shows distribution of drug up to 2 cm (3/4 inch) laterally in intact skin from the electrode.
- Used for acute, local, superficial tissues
Ion Transport
- For DC to be effective pushing drug molecules across the skin, current would need to overcome electrical impedance of the skin
- Difficult for DC = lack of ion transport to opposite electrode
To keep the drug in the area we need to…
keep blood flow low
Can iontophoresis be applied with other agents?
No it should not be applied in conjunction with any agent that may change skin permeability or blood flow.
Ex: Heat, Cold, US
Why use DC?
Need polarity for electroporation and to repel charged ions
AC and pulsed current are ineffective for transferring ions across skin.
Consequences of using DC
Polar Effects
- Skin normally acidic (pH ~ 4.7)
- Salt and water present on skin
- Electric charge creates formation of HCl at Anode and NaOH at Cathode
- AAA – Anode Attracts Acid
- CAB – Cathode Attracts Base
More concerned about NaOH due to skin naturally being more acidic can be more sensitive
Polar Effects - H2O and NaCl
Causes a split. NaCl split then H2O splits. Electrical reaction then chemical reaction results in HCl and NaOH. Skin irritation more likely at NaOH (cathode)
What are good ways to prevent chemical reactions?
- Buffered electrodes decrease likelihood of irritating or burning at the cathode.
- Decreasing current density at that electrode.
– Increasing size of the electrode
– Decrease current levels
– Increase distance between electrodes
Mobile Iontophoresis
- Electrode & battery are one system
- Duration of treatment usually 3-6+ hrs
- Very simple
- Approx. $10-15 per electrode
- Current is low for typically no adverse reactions and most likely won’t feel it
