Iontophoresis is the use of electricity to drive drugs through the skin. It is primarily used in physical therapy to decrease inflammation in a variety of diagnoses, primarily tendonitis, bursitis and post-operatively.
Many patients I treat with iontophoresis are impressed with the results and ask if it is new. I am often surprised that they have never encountered iontophoresis in their prior episodes of physical therapy since it has been commercially available for over 30 years.
The drugs used with iontophoresis must be ionizable; that is, they must become electrically charged when electricity is applied. Therefore, not all substances will work with iontophoresis. The drug is placed on the electrode of the same polarity. Dexamethasone, the very popular steroidal anti-inflammatory commonly known as Dex, is negatively charged. It would be attached to the negative (black) electrode, whereas Lidocaine (a numbing agent) is positively charged, so that would be attached to the positive (red) electrode for delivery.
Iontophoresis is used not only in physical therapy but also in other areas of medicine. This varies from pre-procedural numbing with Lidocaine to pain management with opioids and delivery of antibiotics into wounds.
The Latest Research
In my recent review of the research, the evidence is a fairly consistent body of positive results and kudos for iontophoresis.1-9 Most researchers are still using Dex, but there were also affirmative tests for pain reduction using Ibuprofen and Lidocaine.7,9 The delivery of Botulinum toxin with iontophoresis has also shown up in the literature, with a positive result for decreasing palmar hyperhidrosis without any associated muscle weakness.2
Prior to the introduction of the wireless wearable patches, the common dosage amount was 40 mA/minutes. The dosage pre-set in these portable patches is 80 mA/minutes. The in-clinic devices (with wires!) that have been commonly used turn on at the standard 40 mA/minute dose but are adjustable up to 80 mA/minutes. As a routine procedure, I now set the machines to deliver 80 mA/min in the clinic as well. For more information on what a mA/minute is and how that works please see the very thorough review by Banga et al.1
Doses and Delivery Systems
A note on dosage strengths for comparison: Iontophoresis delivers a therapeutic dose of Dex that is stronger than oral delivery but weaker than injection. Both oral delivery and hypodermic needle delivery of corticosteroids have their risks. Iontophoretic drug delivery provides a safe alternative.
Hypodermic injection of meds is uncomfortable and has systemic and localized side effects such as soft-tissue or fascia weakening or even necrosis.6 Oral administration of corticosteroids has many side effects as well, which vary in severity depending on strength and length of use-ranging from sleep and appetite disturbances to necrosis, osteoporosis, diabetes and more. If delivered properly, the risk with iontophoresis is only skin irritation.
The variety of portable, micro-circuitry iontophoresis delivery systems (or "patches") that originally entered the market a few years ago has increased to quite a selection. They vary in delivery times, buffering and micro-circuitry. For example, the variability in delivery of the drug ranges from within three hours to as long as 24 hours. Some use a reusable power pack, but most are disposable and run on one to five tiny batteries, as in watches.
In addition to the portable patches, I still use the in-clinic systems delivering 80 mA/min of drug within 20 minutes. The patients have variable reports and preferences. Some feel that receiving Dex via the long, slow-delivery time patch reduces their symptoms of pain or swelling more than the fast-delivery system in clinic, but other patients report the reverse. One study demonstrated that long-duration, low-intensity delivery of Dex was superior to short-duration, high-intensity delivery.3
Passive application does not yield tissue concentrations of Dex; this is important data for those patients who wish to wear the patches after the electrical current has ceased.3 I have had some patients who still like to wear them anyway. So as long as they have no allergy to adhesives, it cannot hurt.
The wearable devices are great for those who do not like the feeling of the electricity-those "pins and needles" or "bee stings"-as the amperage is so low it is almost imperceptible. It does present a problem for those with plantar fasciitis, since walking on the patch squeezes the liquid out.
Iontophoresis with Dex has repeatedly proven to be a powerful modality for treatment of many conditions including plantar fasciitis, Achilles tendonitis, peroneal tendonitis, posterior tibial tendonitis, infrapatellar tendonitis, knee, ankle and toe arthritis, bicipital tendonitis, lateral epicondylitis, temporomandibular joint dysfunction, carpal tunnel syndrome, Morton's neuroma, post-operative inflammation, pain, edema and scar.
In one trial on plantar fasciitis, acetic acid performed better than Dex.4 I have no anecdotal comments on this yet, but plan to give it a try.
Despite the overwhelming evidence that iontophoresis is a powerful treatment modality in physical therapy, insurance companies still decline payment. Aetna's Website states: "Aetna considers. iontophoresis (e.g., administration of NSAIDs or corticosteroids) for treatment of inflammatory musculoskeletal disorders. experimental and investigational because of insufficient evidence of its effectiveness."
To get the most out of iontophoresis, there is a logical sequence of treatment. I like to complete the applied heat, ultrasound, massage and exercise before iontophoresis rather than immediately afterward because the increased blood flow could decrease the effectiveness of the treatment by flushing the drug out of the area more quickly.
By the same token, I believe this is a good reason to ice at the same time, since that decreases blood flow. This should be done with care as the manufacturers specifically warn against it. There are several concerns. One is that the icepack may compress the electrode, causing hot spots. Another is the decreased sensation that comes with icing may also increase the chance of injury.
Most of my patients tolerate iontophoresis with ease, but some find it uncomfortable. I would caution to not overly associate the level of stinging with skin damage. There is some correlation, but also many times when the patient has had a poor tolerance with no skin trauma. Ascertain if the burning sensation is over the entire pad versus pinpoint.
Of course it is best to always check the skin if someone feels discomfort, but if it is pinpoint, you will more likely have a problem with blistering. Ensure uniform contact or block the area that is tingling with a tiny piece of tape or petroleum jelly.
Often there is nothing there, but pinpoint histamine blisters may have formed. I explain to the patient that most people report no discomfort with these blisters, which resolve within hours. All but a few think they are well worth the relief of iontophoresis with Dex.
As you use it, you will find that iontophoresis truly is an inexpensive, underutilized and underestimated modality. It has made the experience of rehabilitation less painful for my patients. When they walk out feeling better than when they came in, it improves compliance. Less pain also means healing faster. Lastly, after using iontophoresis in your clinic I hope your patients come back asking for more of "that magic stuff."
Lisa J. Allen owns BioMechanic Physical Therapy in Leesburg, VA, and teaches iontophoresis courses.
1. Banga, A., & Panus, P. (1998). Clinical applications of iontophoretic devices in rehabilitation medicine. Physical and Rehab Medicine, 10(2), 147-179.
2. Davarion, S., Kalantari, K., Rezasoltani, A., & Rahimi, A. (2008). Effect and persistency of botulinum toxin iontophoresis in the treatment of palmar hyperhidrosis. Australian Journal of Dermatology, 49(2), 75-79.
3. Gurney, B., Wascher, D., et al. (2008). The effect of skin thickness and time in the absorption of Dexamethasone in Human tendons usingi iontophoresis. Journal of Orthopedic Sports and Physical Therapy, 5, 238-245.
4. Osborne, H., & Allison, G. (2006). Treatment of plantar fasciitis by LowDye taping and iontophoresis: Short-term results of a double blind, randomized, placebo controlled clinical trial of Dexamethasone and acetic acid. British Journal of Sports Medicine, 000, 1-5.
5. Pellecchia, G., Hamel, H., & Behnke, P. (1994). Treatment of infrapatelllar tendonitis: A combination of modalities and transverse friction massage versus iontophoresis. Journal of Sports Rehabilitation, 3(2), 135-145.
6. Stephenson, R., ed. (2009). Iontophoresis Protocol: Calcaneal Bursitis. IOMED online references; http://seeiomed.com/pdfs/protocols/Protocol%2016%20-%20Calcaneal%20Bursitis.pdf
7. Tascioglu, F., Oner, C., & Armagan, O. (2003). The treatment of lateral epicondylitis with iontophoresis of Ibuprofen and low-level laser. Medical Journal Kocatepe, 1, 22-28.
8. Taskaynatan, M., Ozgul, A., Ozdemir, A., Tan, A., & Kalyon, T. (2007). Effects of steroid iontophoresis and electroptherapy on bicipal tendonisits. Journal of Musculoskeletal Pain, 14(4), 47-54.
9. Yarrobino, T., Kalbfleisch, J., Ferslew, K., & Pandu, P. (2006). Lidocaine iontophoresis mediates analgesia in lateral epicondylalgia treatment. Physiotherapy Research International, 11(3), 152-160. Published_online_in_Wiley_InterScience (www.interscience.wiley.com)_DOI:_10.1002/pri.338