What is Iontophoresis?
Mr. Smith is a 65-year-old man who presents to our office with lateral elbow pain. After performing a physical exam you diagnose him with lateral epicondylosis. He has had no relief from 6 weeks of physical therapy and would like to know what else he can try. Before you can answer he says that he hates needles and refuses to have any injections. Wouldn’t it be nice if there was a way we can deliver medication to a patient’s muscle or tendon without the use of a needle?
Unfortunately for patients, topical medications have poor bioavailability through skin absorption. As a result, researchers discovered that applying an external electrical potential to the skin helps facilitate the travel of ions across a membrane (Nitin Dixit, 2007). This led to the development of iontophoresis which is a process of facilitating transfer of topical medication across the surface of the skin. The principles behind iontophoresis is that two like forces repel each other. What occurs is an anionic medication will be pushed across the skin if placed on an anionic electrode. This is facilitated by the application of a low voltage of electricity (Nitin Dixit, 2007). The typical voltage used is 0.5 mA/cm2. The medication is thought to travel through the pores located in the stratum corneum of the epidermis (Swati Rawat, 2008).
The use of iontophoresis began in other medical specialties including dermatology for treatment of hyperhidrosis and ENT for preoperative anesthesia (Nitin Dixit, 2007). These specialties found that there were advantages to using iontophoresis such as avoidance of hepatic first pass metabolism and direct delivery of a medication to a target area (Nitin Dixit, 2007). There is also no injection so the chance of infection is markedly reduced (Robert Nirschl, 2003). They found minimal side effects with the use of iontophoresis. The most common side effect seen are dermal and may include vesicles and atopic dermatitis at the application site (Robert Nirschl, 2003).
One of the first indications for iontophoresis in the field of musculoskeletal medicine was for the treatment of lateral epicondylitis (Amalia Stefanou, 2012). A study published in the American Journal of Sports Medicine used 2.5mL of 0.4% dexamethasone sodium phosphate and administered it with iontophoresis for the treatment of lateral epicondylitis. The process of using iontophoresis to deliver the dexamethasone over the lateral epicondyle involves applying the dexamethasone to the negative lead and then placing it over the lateral epicondyle. The positive lead will then be placed over a major muscle like the biceps or triceps to complete the circuit (Robert Nirschl, 2003). The dexamethasone is anionic and will be repelled by the negative lead to facilitate delivery of the medication through the skin. The study found that there was less initial pain in the group who received dexamethasone with iontophoresis compared to placebo (Robert Nirschl, 2003). However, at the one month follow up there was no difference in pain compared to placebo. They hypothesized that this may be due to the fact that follow up was completed by telephone and not in person. (Robert Nirschl, 2003).
Image 1. Clinical demonstration of iontophoresis (courtesy of novaphysicaltherapy.com)
A study published in the Journal of Orthopedic and Sports Physical Therapy looked at administering Dexamethasone and Lidocaine with Iontophoresis for myofascial shoulder pain. What they found was that the group that completed the iontophoresis treatment had larger degrees of pain free abduction compared to the group receiving antispasmodics and analgesics (Delcerda, 1982). The authors believed the patient’s myofascial pain was due to muscle spasm due to repeated muscle contraction. By treating the trigger area with dexamethasone and lidocaine with iontophoresis they found improvements in pain (Delcerda, 1982).
Another study published in AJSM was looking at the role of Dexamethasone with Iontophoresis for the treatment of plantar fasciitis. They found that those patients who underwent iontophoresis were found to have more immediate relief of their symptoms compared to the control group undergoing standard care (Scott Gudeman, 1997). This study is useful for physicians and physical therapist who are looking for a rapid way to get their patients to feel better outside of an injection.
When going back to our initial vignette dexamethasone with iontophoresis is a safe and effective way to treat lateral epicondylitis. It has a better safety profile than a corticosteroid injection. In general dexamethasone with iontophoresis is a safe way to treat many common overuse disorders, especially in injuries where the targeted lesion is more superficial.
References
1) Amalia Stefanou, N. M. (2012). A Randomized Study Comparing Corticosteroid Injection to Corticosteroid Iontophoresis for Lateral Epicondylitis. Journal of Hand Surgery, 104-109.
2) Delcerda, F. (1982). A Comparative Sudy of Three Methods of Treatment for Shoulder Girdle Myofascial Syndrome. The Journal of Orthopaedic and Sports Physical Therapy, 51-54.
3) Nitin Dixit, V. B. (2007). Iontophoresis-An Approach for Controlled Drug Delivery. Current Drug Delivery, 1-10.
4) Robert Nirschl, D. R. (2003). Iontophoretic Administration of Dexamethasone Sodium Phosphate for Acute Epicondylitis. The American Journal of Sports Medicine, 189-195.
4) Scott Gudeman, S. E. (1997). Treatment of Plantar Fasciitis by Iontophoresis of 0.4% Dexamethasone. The American Journal of Sports Medicine, 312-316.
5) Swati Rawat, S. V. (2008). Transdermal Delivery by Iontophoresis. Indian Journal of Pharmaceutical Sciences, 5-10.
