An Introduction to Iontophoresis
Iontophoresis, or “electrically assisted
transdermal drug delivery” is a method of delivery of ionic substances through
the skin, which is assisted or enhanced with an electric charge. This current
being delivered can be turned on and off hereby controlling the release of
solutes through the skin. Iontophoresis is used by physiotherapists for the
delivery of anti-inflammatory medication for the treatment of plantar
fasciitis, bursitis and a plethora of other clinical indications (Khan et al,
2011). The substance being transferred through the skin enters the circulation
through the capillaries. This is beneficial for administration of some drugs as
it avoids first pass clearance by the liver, enzymes and acidic or basic
substances in the gastrointestinal tract (Khan et al, 2011). Currently,
handheld devices are popular for Iontophoresis treatment (see Figure 1).
Figure 1: Chattanooga Ionto Device (Chattanooga Ionto Device, n.d.).
In terms of the popularity of
Iontophoresis, few drugs are delivered this way in comparison to other routes.
However, its use is increasing at a projected rate of 12% per annum, with 35
active ingredients approved by the Food and Drug Administration in the United
States and 16 active ingredients approved for use worldwide. In 2005,
Iontophoresis had a market of $12.7B and this is projected to increase
substantially to $31.5B by 2015 (Prausnitz, Mitragotri & Langer 2004).
History
Although currently the use of Iontophoresis
is rapidly becoming widespread, the technique has been centuries in the making.
The first notable literature published was in 1747 by Giovanni Pivati. After
applying an electric current to a scented plant in a sealed jar, the smell
penetrated the container. It was not until the 1850’s when it was first
suggested that the application of electric current could be used for medication
delivery (Helmstadter, 2001). From that time, several different substances were
experimented with for their affinity for transdermal delivery (see Table 1).
(Helmstadter, 2001)
Transdermal delivery of ionized drugs
without the aid of electric current had previously been rarely used due to the
slow rate of diffusion powered only by the concentration gradient. With the
application of the current techniques of Iontophoresis, transdermal delivery of
these drugs is now desirable (Wang et al., 2005).
A safe, reliable method of Iontophoresis
was first introduced in the US in 1989, however was never successful. Since
then, technology has caught up, with the development of new products entering
the market and making the process compatible with more drugs, and broadening
the clinical indications for use.
Principles of Iontophoresis
Iontophoresis involves two electrodes, the
cathode and the anode (see Figure 2). For a drug that is negatively charged,
the drug must be dissolved in a solution and loaded into the cathode
(negatively charged electrode). This electrode should be placed directly over the lesion and the anode is then placed a few centimetres away on the skin (Khan et al., 2011). As the drug and the electrode in which it is loaded have a
like charge, the drug will move through the stratum corneum (the outer layer of
the epidermis) towards the anode. Drugs with neither a positive nor negative
charge also move through the skin due to osmotic/electro-osmotic forces when a
current is applied (Khan et al., 2011).
Figure 2: Electrode placement and drug
delivery (TCT Summary, n.d.).
The history has been covered in todays blog, next up we will discuss the dosage guidelines that need to be understood and adhered to during administration of iontohphoresis.
Wang, Y., Thakur, R., Fan, Q. &
Michniak, B. (2005). Transdermal iontophoresis: combination strategies to
improve transdermal iontophoretic drug delivery. European Journal of Pharmaceutics and Biopharmaceutics, 60(2),
179-191.
Khan, A., Yasir, M., Asif, M., Chauhan, I.,
Singh, A., Sharma, R., Singh, P., Rai, S. (2011). Iontophoretic drug delivery:
history and applications. Journal of
applied pharmaceutical science, 1(3), 11-24.
Helmstadter, A. (2001). The history of
electrically-assisted transdermal drug delivery. Pharmazie, 56(7), 583-587.
Prausnitz, M., Mitragotri, S. & Langer,
R. (2004). Current status and future potential of transdermal drug delivery. Drug Discovery, 3(2), 115-124.