Iontophoresis is a physical therapy technique that uses a mild electrical current to push medication through your skin and into the inflamed or painful tissue underneath. Instead of swallowing a pill or getting an injection, the drug goes directly to the problem area, whether that’s a swollen tendon, an arthritic knee, or a tight band of scar tissue. Sessions typically last 15 to 40 minutes, and it’s one of several tools physical therapists use alongside exercise and manual therapy.
How the Electrical Current Delivers Medication
The basic principle is simple: charged particles move when exposed to an electric field. Medications used in iontophoresis carry either a positive or negative charge when dissolved in solution. A small device applies a low-level direct current through two electrode pads placed on your skin. One pad holds the medication, and the other completes the circuit. The electrical current repels the charged drug molecules away from the electrode and drives them through the outer layers of skin into the tissue below.
The process works because skin, at a microscopic level, behaves like a capacitor in an electrical circuit. Each charged drug molecule travels surrounded by a small shell of water molecules, and the current essentially pushes this entire package through the skin’s natural pathways, including sweat glands and hair follicles. Over the course of a session, the skin’s resistance to the current gradually increases, which is why treatment dosage is carefully calculated as a product of current intensity and time, measured in milliamp-minutes. A typical session delivers between 40 and 80 milliamp-minutes.
Medications Used in Iontophoresis
The medication your physical therapist selects depends entirely on what’s being treated. The most common options in a PT setting fall into a few categories:
- Anti-inflammatory steroids: Dexamethasone is the most widely used. It reduces inflammation in joints, tendons, and bursae. It’s delivered from the negatively charged electrode.
- Local anesthetics: Lidocaine numbs the treatment area and is useful for acute pain or as a first step before other manual therapy techniques.
- NSAIDs: Anti-inflammatory drugs can target osteoarthritis, joint injuries, and acute pain in a specific area without the systemic side effects of oral pills.
Because the drug goes directly into the tissue, far less medication is needed compared to an oral dose, and the rest of your body isn’t exposed to it. This localized delivery is the main advantage over a pill, and it avoids the needle that comes with a cortisone shot.
Conditions It Treats
Physical therapists most commonly use iontophoresis to reduce inflammation and pain in musculoskeletal conditions. The list includes tendonitis (especially patellar and Achilles tendon issues), bursitis, plantar fasciitis, and osteoarthritis. It’s also used to manage scar tissue after surgery, decrease localized swelling, reduce calcium deposits in soft tissue, and relieve muscle spasms.
A study on knee osteoarthritis with Baker’s cysts found that patients receiving dexamethasone iontophoresis alongside a standard physiotherapy program had significant improvements in both resting and exercise pain scores within two weeks. The improvement held at six weeks as well. Cyst volumes also decreased more in the iontophoresis group compared to patients who received only standard physiotherapy. The takeaway: iontophoresis appears to accelerate pain relief and functional recovery when added to a broader rehab program, though it’s rarely used as a standalone treatment.
What a Session Feels Like
Your therapist will clean the skin over the treatment area and place two adhesive electrode pads. One contains the medication, and the other serves as the return electrode, usually placed a few inches away. Once the device is turned on, you’ll feel a mild tingling or slight prickling sensation under the electrodes. Some people also notice a faint itching during the first half-hour of current flow. The sensation should never be painful. If it becomes uncomfortable, the current intensity can be lowered immediately.
After the session, mild redness under the electrode is normal and usually fades within a few hours. In clinical studies, iontophoresis caused only transient, mild skin irritation (slight redness and minor swelling) that resolved without any permanent skin damage.
Wired Units vs. Wireless Patches
Traditional iontophoresis uses a tabletop dose controller connected by two wires to the electrode pads. You sit or lie still while the device runs for 15 to 40 minutes. This is the setup you’ll encounter in most PT clinics.
Newer wireless patches contain a tiny battery and microchip built directly into the electrode. These deliver the same total dosage (usually around 80 milliamp-minutes) but at much lower current over a longer period, anywhere from 3 to 14 hours. The advantage is that you can wear the patch while going about your day. Early versions had reliability issues because a single small battery couldn’t always overcome skin resistance, but current designs use a microchip that monitors skin resistance in real time and adjusts the current accordingly. Your therapist may apply a wireless patch at the end of a visit and have you remove it at home.
Typical Treatment Schedule
There’s no single standardized protocol, but most treatment plans involve 3 to 5 sessions per week. Each session lasts 10 to 30 minutes of active current delivery. Therapeutic effects generally appear after 6 to 15 treatments, so a typical course runs roughly two to four weeks. Your therapist will likely reassess your pain and function partway through to decide whether to continue, and iontophoresis is almost always paired with therapeutic exercises, stretching, or other PT interventions.
Who Should Avoid Iontophoresis
Iontophoresis is considered safe for most people, but there are clear situations where it shouldn’t be used. Anyone with a known allergy or sensitivity to the medication being delivered should avoid it. The electrical current also creates restrictions: people with cardiac pacemakers, implanted metal hardware near the treatment site, or a history of cardiac arrhythmias are not candidates. The electrodes should never be placed over broken skin, open wounds, or areas with impaired sensation, since you wouldn’t be able to feel if the current were too strong. Its safety during pregnancy hasn’t been studied, so most clinicians avoid it in pregnant patients.
If you have a bleeding disorder or take blood thinners, let your therapist know, as the procedure should not be performed near superficial blood vessels in patients with hypercoagulability concerns. These precautions are straightforward, and your physical therapist will screen for them before your first session.