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July 2005


Fighting Inflammation

By Michelle H. Cameron, MD, PT, OCS

Iontophoresis has been shown to alleviate painful conditions such as arthritis

Iontophoresis is a way to deliver a medication to a patient through the skin using an electrical current. It is based on the principle that like charges repel. With a direct current, an electrical charge can be applied to an ion of a drug with the same charge and the drug ion will be pushed away through the skin. This approach to drug delivery dates back to the 19th century, marked by ongoing technical improvements and research clarifying its treatment outcomes.

Iontophoresis can be used to deliver a wide range of medications, although in rehabilitation it is primarily used to deliver the anti-inflammatory drug dexamethasone (see Table 1). This is the most popular and well-researched application of iontophoresis in rehabilitation.

ANTI-INFLAMMATORY BENEFITS
Dexamethasone is a corticosteroid drug that is used primarily for its anti-inflammatory effects. In rehabilitation, it is used most often for the treatment of soft tissue and other musculoskeletal inflammation. When used for iontophoresis, dexamethasone must be in the form of a dexamethasone sodium phosphate solution. In this form, the drug forms negatively charged ions of dexamethasone phosphate that can be driven through the skin with the negatively charged iontophoresis electrode.

Treatment with iontophoretically delivered dexamethasone has been shown in controlled clinical trials to help patients with medial and lateral epicondylitis, rheumatoid arthritis of the knee, Achilles tendinitis, plantar fasciitis, and temporomandibularjoint (TMJ) dysfunction. This treatment was found to be more effective and/or more rapidly effective than placebo treatment or traditional modalities alone. Treatment with dexamethasone iontophoresis reduced pain and improved function in patients with this wide range of inflammatory conditions. Iontophoresis with dexamethasone is thought to be most effective as a component of treatment when there is inflammation of superficial structures close to the site of the delivery electrode. This treatment is likely to be less effective when there is inflammation of deeper structures, because the drug becomes more diluted as it gets further away from the delivery electrode. As with other modalities, this treatment should be combined with other interventions for an optimal clinical outcome.

Table 1

Table 1


RESEARCH DEFICIT
Although the use of iontophoresis to deliver a wide range of other medications for a plethora of conditions has been reported, there is a paucity of well-designed and well-controlled clinical trials evaluating the effectiveness of most of these treatments. For example, although in a number of published case studies it described how patients with calcific tendinitis improved with iontophoresis with acetic acid, two fairly recent clinical trials failed to show that iontophoresis with acetic acid for the treatment of calcific tendinitis was any more effective than conventional physical therapy alone. Although the small numbers of patients in these trials call their findings into question, the results do suggest that a healthy dose of skepticism is needed when applying treatments for conditions that tend to resolve well with or without intervention, and for those that respond well to current approaches to treatment.

One other area where a number of trials have shown iontophoresis to be effective is in the delivery of the anesthetic drug lidocaine for local anesthesia of the skin prior to injection or other painful procedures such as lumbar puncture. This approach to drug delivery has been found to be as or more effective than delivery of the same drug by injection. It produces a quicker onset of effect with less pain, and it is better tolerated by many patients, particularly children.

TREATMENT PARAMETERS
For iontophoresis to be effective, a number of conditions must be met. The drug must be in the appropriate form, and the appropriate electrical charge and dose must be used. The drug must be in an ionized form in solution, and it must be applied with either a buffered electrode or together with a buffering solution to prevent the formation of gas bubbles as the water hydrolyzes at both electrode sites. The drug itself must also be stable when a current is applied to it. Since iontophoresis is based on the principle that like charges repel, the charge of the drug-ion and of the drug-application electrode must be the same.

For example, when delivering dexamethasone phosphate, which is a negatively charged ion, the negatively charged electrode should be used to deliver the drug. When delivering lidocaine, which forms a positively charged ion, the positively charged electrode should be used to deliver the drug. To complete the electrical circuit, a second electrode without any medication and of the opposite charge must also be used. This electrode should be placed on the patient about four to six inches away from the area of the pathology being treated.

Table 2

Table 2

The dose of electricity recommended for iontophoresis is based on the amount of current that is flowing and the amount of time for which it flows. This dose is generally described in terms of milliamp minutes (mA.min). The recommended milliamp-minute dose varies among electrodes; but for most electrodes available today, it is around 40 mA.min; 40 mA.min may be delivered by various combinations of current and time, as shown in the examples in Table 2.

When a consistent amount of electricity (mA.min) is used, a similar amount of medication will be delivered. With most iontophoresis equipment available today, the current flow (number of mA) is set according to patient comfort. The clinician then selects the total mA.min dose, and the treatment device determines the amount of time the treatment should last to achieve this dose. In addition, there are now iontophoresis devices available today, the current flow (number of mA) is set according to patient comfort. The clinician then selects the total mA.min dose, and the treatment device determines the amount of time the treatment should last to achieve this dose. In addition, there are now iontophoresis devices available from a number of manufacturers that deliver a similar dose of electricity by running a very low level of current (a few microamps) for many hours. With this type of device, the power for the treatment is inside the disposable electrode, and the current runs down at the end of the treatment period.

TREATMENT ADVANTAGES
Iontophoresis offers a number of advantages over other drug delivery methods, and is one of the only drug delivery methods used by rehabilitation-allied health clinicians today. It avoids the risks of infection and skin damage, and the discomfort associated with delivering drugs by injection. It can also deliver a greater concentration of medication to a local area than oral medications, and it reduces the risk of systemic side effects by delivering a very low systemic dose.

To apply an iontophoresis treatment, one needs specialized iontophoresis electrodes, a direct current source—usually the iontophoresis unit, although now this may be incorporated into the electrode for the low-current, long-duration electrodes—and the medication solution. First, review contraindications to the electrical stimulation and the medication with the patient. Then, thoroughly clean the area of the skin where the electrodes will be placed with an alcohol wipe. The treatment electrode should be placed as close to the tissue to be treated as possible, on an intact and relatively flat area of skin. Hydrate the delivery electrode with the medication solution, and place it on the area to be treated. Place the other electrode four to six inches away from the treatment electrode. Then, connect the electrodes to the leads, and connect the leads to the device. Select the desired dose of electricity (mA.min) and a well-tolerated level of current. The device will now run until the treatment is completed. This usually takes 10 to 15 minutes.

When the treatment is completed, turn off the device, remove the electrodes, and inspect the patient’s skin. It is not unusual for the area under either or both of the electrodes to be slightly red. Some recommend applying an unscented, nongreasy skin lotion and/or a few minutes of ice after treatment with iontophoresis to calm these sites.

Iontophoresis is an effective, well-tolerated, and easy-to-use method for delivering ionized medications through the skin with an electrical current. It provides a comfortable, safe, and effective option for the treatment of a wide range of pathologies. Within rehabilitation in particular, delivery of dexamethasone with iontophoresis for the treatment of inflammatory conditions has been shown to relieve symptoms associated with a wide range of conditions. The use of this treatment modality, in conjunction with other interventions, including exercise, activity modification, and manual therapy, may accelerate symptom resolution and help optimize clinical outcomes in a wide range of patients.

Michelle H. Cameron, MD, PT, OCS, is a physician and a physical therapist. She is a renowned clinician, teacher, researcher, and author. She has lectured worldwide on a variety of topics related to physical agent modalities. Cameron wrote and published the textbook, Physical Agents in Rehabilitation: From Research to Practice, which is now in its second edition. Her research on physical agent modalities has been published in several journals and has earned her the California APTA Clinician Research Award.Cameron also wrote the section on ultrasound in Saunders Manual of Physical Therapy Practice. Her courses on ultrasound, electrical stimulation, lasers, thermal agents, and the use of modalities for wound healing bring together current research and practice to provide participants with the decision-making and hands-on tools to provide optimal care within today’s evidence-based health care environment.

REFERENCES
  1. Nirschl RP, Rodin DM, Ochiai DH, et al. Iontophoretic administration of dexamethasone sodium phosphate for acute epicondylitis. A randomized, double-blinded, placebo-controlled study. Am J Sports Med. 2003;31:189-95.
  2. Li LC, Scudds RA, Heck CS, Harth M. The efficacy of dexamethasone iontophoresis for the treatment of rheumatoid arthritic knees: a pilot study. Arthritis Care Res. 1996;9:126-32.
  3. Neeter C, Thomee R, Silbernagel KG, et al. Iontophoresis with or without dexamethasone in the treatment of acute Achilles tendon pain. Scand J Med Sci Sports. 2003;13:376-82.
  4. Gudeman SD, Eisele SA, Heidt RS Jr, et al. Treatment of plantar fasciitis by iontophoresis of 0.4% dexamethasone. A randomized, double-blind, placebo-controlled study. Am J Sports Med. 1997;25:312-6.
  5. Schiffman EL, Braun BL, Lindgren BR. Temporomandibular joint iontophoresis: a double-blind randomized clinical trial. J Orofac Pain. 1996;10:157-65.
  6. Perron M, Malouin F. Acetic acid iontophoresis and ultrasound for the treatment of calcifying tendinitis of the shoulder: a randomized control trial. Arch Phys Med Rehabil. 1997;78:379-84.
  7. Leduc BE, Caya J, Tremblay S, et al. Treatment of calcifying tendinitis of the shoulder by acetic acid iontophoresis: a double-blind randomized controlled trial. Arch Phys Med Rehabil. 2003;84:1523-7.
  8. Zempsky WT, Sullivan J, Paulson DM, et al. Evaluation of a low-dose lidocaine iontophoresis system for topical anesthesia in adults and children: a randomized, controlled trial. Clin Ther. 2004;26:1110-9.


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