Iontophoresis or Phonophoresis
Iontophoresis or Phonophoresis
ADVANCE highlights the latest clinical research
Few modalities have been the target of as much controversy and speculation as iontophoresis and phonophoresis. But the allure of administering medications without pill or needle appeals to both patient and practitioner alike. While mounting clinical research supports the positive outcomes the modalities can offer, it is the results seen in the clinic that encourage PTs to use them.
"There are three criteria for these two modalities to be successful," explained Jim Smith, PT, clinical manager of Nova Care Rehabilitation, St. Paul, MN. "The condition must be acute, local and inflamed." If Smith is unable to pinpoint the injury to a location roughly the size of a silver dollar, iontophoresis will not be his modality of choice.
Multiple alternatives exist for delivering medications transcutaneously, from injection to topical administration. Transcutaneous delivery bypasses the stomach and liver, which can cause adverse effects or dilute the compound, and can allow administration to a localized area.
Iontophoresis: Clinical Research
Sports injuries are the most common application of iontophoresis, with some success also seen in patients with temporomandibular disease, trigger points, osteoarthritic flare-ups, calcium deposits, excessive scarring, bursitis and tendonitis, Smith explained.
New devices on the horizon work on the same principle as the nicotine patch, Smith said. A self-contained device with a built-in computer chip creates a chemical battery, delivering an ultra-low current through electrodes over a prolonged period of time (up to 24 hours). "The theory is that if we bathe the inflamed tissue over a long period, it will more effectively reduce pain and swelling," he said. Other benefits to this treatment are increased mobility during treatment and reduced skin irritation and burn risk.
In a 1999 study published in Physical Therapy, researchers conclude, "Compared with passive delivery, iontophoresis enhances nonstereoselective ketoprofen permeation into the fascia-muscle interface."1 However, the same study found that iontophoretic delivery to deeper tissues was equal to passive application.
In 1998, Dutch researchers demonstrated the action of iontophoresis of R-apomorphine delivery in patients with Parkinson's disease. "It is concluded that the delivery of R-apomorphine by transdermal iontophoresis may be an attractive tool in future clinical pharmacological investigations in patients with Parkinson's disease..."2
But according to a 2000 study in which researchers scoured Medline articles from 1966 to 1997, iontophoresis showed "limited evidence" in easing the pain of the plantar heel.3
Phonophoresis: Clinical Research
The efficacy of phonophoresis remains a more hotly debated topic. Clinical research can be found to support both sides of the issue, but phonophoresis, the use of ultrasound to deliver medication into muscle tissue, is generally the lesser-used of the two modalities. While some research suggests it may be effective, critics are quick to point to the placebo effect--and to the fact that positive outcomes are the result of the ultrasound itself--to explain favorable research results.
In a 1999 study, phonophoresis was found effective in the treatment of two middle-aged women with calcific tendonitis of the shoulder.
Both patients complained of chronic pain and tenderness in the shoulder, and had a limited range of shoulder motion. Radiographs showed calcific deposits in the region of the supraspinatus tendon.
Twenty sessions of phonophoretic application of Movelat cream were followed by cross-friction massage to the tendon and range of motion exercises. A second set of radiographs showed no visible calcific deposits, and after four months the subjects remained symptom-free.4
Further support comes from MIT researchers, who in January 2000 reported that "Low-frequency (20 kHz) ultrasound has been shown to enhance transdermal transport of drugs, a phenomenon referred to as sonophoresis."5
In a contrasting 1996 study, often cited by opponents of the technique, 16 asymptomatic men and women between the ages of 18 and 33 years were administered topically applied 10 percent hydrocortisone acetate. Ultrasound was delivered over a 50 square-centimeter area for five minutes. Blood was drawn under control (ultrasound) and experimental (hydrocortisone plus ultrasound) conditions, and no rise in serum cortisol concentrations was detected. The authors suggest that the ultrasound resulted in no penetration of hydrocortisone through the epidermis and into the underlying vasculature.6
Finally, a study by researchers in the rehabilitation medicine department of the National Institutes of Health found no difference in pain levels in patients who received ultrasound and ultrasound plus phonophoresis. Forty-nine subjects with soft tissue injuries received eight minutes of continuous ultrasound treatments three times per week for three weeks. One group also received a gel containing 0.05 percent fluocinonide. While both groups showed a reduced pain level and pressure tolerance, the reductions were comparable enough for researchers to conclude, "The addition of [phonophoresis] with fluocinonide does not augment the benefits of [ultrasound] used alone."7
Any new technique will carry corresponding skepticism by patients.
"The biggest patient concern is not the fear of burns or discomfort, but the fact that they're being given steroids, and all the negative connotations associated with that," Smith said. "I'll sit down and explain that this is a very low concentration of cortisone, administered in a measured amount over a very short period of time. That usually puts them at ease."
While electromechanical burns used to be a danger, new technology has improved the electrodes' efficiency and reduced the risk of injury.
"I think a common misconception is that a patient can be burned by iontophoresis," said John Spangenberg, PT, owner of Physical Therapy Workshop, Coatesville, PA. "This is nearly impossible with today's technology." He added that because many patients prepare for discomfort, he'll have to assure them that the modality is working even though they don't feel anything.
Cortisone is far and away the most common compound used with iontophoresis and phonophoresis. Lidocaine, another FDA-cleared analgesic, was favored by earlier therapists for its inherent buffering effect, but improvements in electrode design have greatly reduced lidocaine's use.
"Technique is very important with any modality, but especially phonophoresis," Spangenberg said. "The angle of the soundhead and speed of soundhead motion can have a major effect on treatment outcomes."
Both therapists prefer iontophoresis to phonophoresis; in fact, Smith hasn't used the latter in three to four years.
Smith received his education of the modalities through years of trial and error. "I gathered information from equipment manufacturers, journal articles, and 18 years of learning what works and what doesn't," he said. "It's certainly not the only tool to use, but for certain acute injuries I believe [iontophoresis] works extremely well." Both PTs advise their colleagues to see for themselves what the two techniques can do.
"My advice to any clinician not familiar with a modality is to try it out," Spangenberg said. "Only then can they find out what a useful adjunct it can be to treatment." *
1. Panus, P., et al. (January 1999). Ketoprofen tissue permeation in swine following cathodic iontophoresis. Physical Therapy, 79(1), 40-49.
2. Bodde, H.E., et al. (Sept. 7, 1998). An integrated pharmacokinetic-pharmacodynamic approach to optimization of R-apomorphine delivery in Parkinson's disease. Adv Drug Deliv Rev, 33(3), 253-263.
3. Crawford, F., et al. (2000). Interventions for treating plantar heel pain. Cochrane Database Syst Rev, (3), CD000416.
4. Gimblett, P.A., et al. (1999 Nov.-Dec.). A conservative management protocol for calcific tendonitis of the shoulder. Journal of Manipulative Physiological Therapy, 22(9), 622-627.
5. Mitragotri, S., et al. (Jan. 3, 2000). Determination of threshold energy dose for ultrasound-induced transdermal drug transport. Journal of Control Release, 63 (1-2), 41-52.
6. Bare, A.C., et al. (1996). Phonophoretic delivery of 10 percent hydrocortisone through the epidermis of humans as determined by serum cortisol concentration. Physical Therapy, 76, 738-749.
7. Klaiman, M.D., et al. (September 1998). Phonophoresis versus ultrasound in the treatment of common musculoskeletal conditions. Medical Science Sports Exercise, 30(9), 1349-1355.
Jonathan Bassett is on staff at ADVANCE, and can be reached at firstname.lastname@example.org.