Iontophoresis. Physical and biophysical principles. Selection of polarity and pharmacological agents. Application techniques, dosage, indications, contraindications, and safety considerations
Iontophoresis uses a direct current to push charged drug molecules through the skin. This page covers how it works, how the polarity and the drug are chosen, how it is applied and dosed, what it is used for, and when it must not be.
- 9 min read
- 5 questions
- Checked 05 Nov 2026
Contents7 sections
At a glance
- Iontophoresis drives a charged drug into the skin with a direct current. Like charges repel: a positive drug goes under the anode, a negative one under the cathode.
- The drug must dissolve in water and split into ions, and small molecules with a single charge travel best. The current also drags water and dissolved neutral molecules from anode to cathode (electro-osmosis).
- The effect is mostly local: a high concentration in skin and the tissue just below, a skin depot that releases slowly, little in the blood.
- The dose is the charge delivered, current times time, in mA·min: often 40 to 80 mA·min, at a current density of about 0.1 to 0.5 mA/cm², 5 to 20 minutes, 10 to 25 sessions (shorter courses for steroids).
- Common drugs: lidocaine (anode) for pain, dexamethasone (cathode) for tendinopathy and plantar fasciitis, tap water for hyperhidrosis; the old school also uses magnesium, calcium, iodide, salicylate and others.
- It has every contraindication of galvanization plus allergy or any contraindication to the drug. The main risk is still a burn under the electrode.
- The exact dose that reaches tissue cannot be measured, and good trials show mostly short-term benefit.
Physical and biophysical principles
Electrotherapy with a direct current moves ions, so if a drug is an ion, the current can carry it into the body. Iontophoresis (the Russian school calls it medicinal electrophoresis) is exactly that: a drug solution under an electrode of the same sign, and a galvanic current to push it in.
Think of the electrode as a hand pushing a ball away. A positive electrode pushes positive ions away from itself, into the skin and onwards towards the negative electrode. Without the current, the skin's outer layer keeps most drugs out; with it, they are driven through.
Three ways the drug moves
| Mechanism | What happens | Which drugs |
|---|---|---|
| Electromigration (electrorepulsion) | Charged molecules are pushed away from the electrode of the same sign | Every ionised drug; the main mechanism |
| Electro-osmosis | The skin carries a negative charge at body pH, so the current drags water, with whatever is dissolved in it, from anode to cathode | Helps positive drugs under the anode; carries neutral molecules a little |
| Opened pathways | Most drug enters through sweat ducts and hair follicles, where resistance is lowest; the current may also loosen the outer skin for a while | All |
Point at a name or a part to light it.
Like charges repel: a positive drug goes under the anode and a negative one under the cathode, and the current pushes each away from its electrode into the skin. The dry horny layer keeps most of it out, so most enters through sweat ducts and hair follicles, where resistance is lowest, then spreads into the skin and the tissue just below; little reaches the blood. The other electrode closes the circuit. Here each electrode carries a drug, to show both; in practice one carries the drug and the other, usually larger, only returns the current.
Simplified: each electrode carries a drug, to show both charges; in practice one electrode carries the drug and the other, usually larger and some distance away, only closes the circuit; not to scale: the drug molecules, ducts and follicles are drawn far larger than life and few, and the layers' thicknesses are not true; the current spreads through the tissue rather than running in a band, and much of it passes through the ducts and follicles too; how deep the drug reaches is not measured: most stays in the skin and the tissue just below, and some is carried off by the blood.
4 sources
- Aleksiev AR. Physical Medicine and Rehabilitation, lecture 1 handnotes. Medical University of Sofia, 2026. Iontophoresis: definition and principle, requirements and pharmacokinetics.
- Aleksiev A. Physical Medicine and Rehabilitation for English-speaking MD students. Medical University of Sofia, 2002. Iontophoresis: requirements, pharmacokinetics of the iontophoretic drug.
- Cameron MH. Physical Agents in Rehabilitation, an evidence-based approach to practice, 5th edition. Elsevier, 2018. Iontophoresis.
- Watson T, Nussbaum EL (eds). Electrophysical Agents, evidence-based practice, 13th edition. Elsevier, 2021.
What happens inside: the professor's account
The book adds an older model. A good iontophoretic drug has "status nascendi" ability: before it enters the skin it is electrically very active and chemically quiet, so the current moves it; once inside, it gives up its charge and becomes chemically active, so it acts. And drugs behave in three ways, by the size and charge of their particles:
| Drug particles | What they do |
|---|---|
| Small, single charge | Penetrate fastest and are carried away in blood and lymph: some systemic effect |
| Medium, double charge | Lose their charge in the peripolar zone and act there: the local effect |
| Large, triple charge or more | Penetrate slowest and stay in the skin as a depot, released over hours to days |
The modern view is similar in spirit: small, highly charged, water-soluble molecules at a high concentration move best; most of the drug stays in skin and tissue just below; and the current itself adds the effects of galvanization.
Requirements
- A direct (monopolar) current, or a pulsed monophasic current with a direct-current component. An alternating or balanced biphasic current pushes the drug one way and pulls it back the next.
- A drug that dissolves in water and splits into ions at the pH of the solution, stable in the current, and active in small amounts.
- A solution without other competing ions: salt, buffers or sweat carry part of the current instead of the drug. Drugs are dissolved in distilled water where possible.
- Healthy, clean, hydrated skin.
Selection of polarity and pharmacological agents
Choosing the polarity
The polarity is fixed by the drug's charge, and the electrode's own effect comes as a bonus: a drug under the anode adds the calming, anti-oedema effect of the anode; one under the cathode adds the stimulating, softening effect of the cathode.
Common drugs
| Drug or ion | Charge, electrode | Traditional or current use |
|---|---|---|
| Lidocaine (or procaine, the old novocaine) | Positive, anode | Local pain, before small procedures |
| Dexamethasone sodium phosphate | Negative, cathode | Tendinopathies, plantar fasciitis, lateral epicondylalgia, bursitis |
| Tap water (sometimes with glycopyrronium) | Both, polarity reversed halfway | Palmar and plantar hyperhidrosis |
| Salicylate | Negative, cathode | Local pain, soft-tissue conditions (traditional) |
| Magnesium (magnesium sulfate) | Positive, anode | Muscle spasm and hyperexcitability (traditional) |
| Calcium (calcium chloride) | Positive, anode | Post-traumatic and inflammatory conditions, a "desensitising" effect (traditional) |
| Iodide (potassium iodide) | Negative, cathode | Scars, adhesions, chronic inflammation (traditional, to "soften" tissue) |
| Acetate (acetic acid) | Negative, cathode | Calcific deposits such as calcific tendinitis (traditional, weak evidence); also tried in plantar fasciitis |
| Pilocarpine | Positive, anode | The sweat test for cystic fibrosis: it makes the skin sweat so that sweat chloride can be measured |
Application techniques
The technique is the galvanic one, with the drug added.
- 1
Prepare
Check contraindications, including allergy to the drug. Clean, dry, intact skin; no creams. - 2
Load the electrode
Soak the drug solution into a thin filter-paper layer or the pad of the active electrode (or use a ready drug-holding electrode). The drug side touches the skin. - 3
Place
Active electrode over the target, the return electrode some distance away (several centimetres or more, on a larger area), so the current passes through the target and not just between the edges. - 4
Connect
Active electrode to the pole with the drug's sign. Check the polarity twice: the wrong pole pushes the drug away from the skin. - 5
Treat
Raise the current slowly to a light tingling, keep contact even, watch the skin and ask how it feels. - 6
Finish
Lower to zero, remove, inspect the skin, record drug, concentration, polarity, current, time and reactions.
Variants are the same as for galvanization: local, segmental and reflex techniques, and baths in which the drug is dissolved in the water. Modern options include buffered, self-adhesive drug electrodes and small battery-powered patches worn for hours at a low current.
Dosage
The dose of drug actually reaching the tissue cannot be measured, so the dose is described by the electricity: the charge delivered.
- typical charge per session in modern protocols (dexamethasone often 40)
- 40–80mA·min
- current density, lower for the cathode and for sensitive skin
- 0.1–0.5mA/cm²
- per session, at up to about 4 mA in most modern protocols
- 5–20minutes
- Charge = current × time. 40 mA·min is 4 mA for 10 minutes or 2 mA for 20 minutes; it equals 2.4 C.
- Current density = current ÷ electrode area. 2 mA through a 10 cm² electrode is 0.2 mA/cm².
- The course is 10 to 25 sessions by the professor's material, daily or every other day; steroid courses are shorter (the main dexamethasone trials gave six sessions over two weeks). Hyperhidrosis needs sessions several times a week at first, then maintenance.
- Raise the dose slowly if the skin tolerates it well and the effect is too small; lower or stop if there is discomfort, burning, strong redness or warmth.
Strengths and limits
| Advantages | Disadvantages |
|---|---|
| No needle, no pain, little risk of infection | The dose reaching the tissue cannot be known exactly |
| High concentration where it is wanted, little in the blood, so fewer systemic side effects | High blood levels cannot be reached (by the same token) |
| A skin depot keeps acting after the session | Only water-soluble, ionisable drugs work |
| The current adds its own effects | Burns and irritation from the current; allergy to the drug |
Indications
The indications are those of galvanization plus those of the drug. Grouped by reason:
- Pain from superficial structures: lidocaine for local anaesthesia, salicylate and other analgesic ions in the old school.
- Inflammation of tendons, fascia and bursae near the surface: dexamethasone for plantar fasciitis, lateral epicondylalgia, tendinopathies of the shoulder and elbow, bursitis, the hand and wrist (de Quervain tenosynovitis).
- Overactive sweat glands: tap water for palmar and plantar hyperhidrosis.
- Scars, adhesions, calcium deposits and chronic inflammation: iodide, acetate and similar ions (traditional).
- Muscle spasm: magnesium (traditional).
- Diagnosis: pilocarpine for the sweat test.
Contraindications
Everything that rules out galvanization rules out iontophoresis, because it is a direct current. Then come the drug's own contraindications.
| Reason | Contraindication |
|---|---|
| From the current | Pacemaker or implanted defibrillator in the current path; metal implants in the path; pregnancy (abdomen, pelvis, low back); malignant tumour in the area; active bleeding and bleeding disorders; acute deep vein thrombosis; severe arrhythmia; fever and acute infection; acute inflammation; epilepsy (head) |
| From the skin | Open wounds, broken, infected or diseased skin; loss of sensation in the area; a patient who cannot cooperate |
| From the drug | Allergy or hypersensitivity to the drug (and to its class: an allergy to amide local anaesthetics rules out lidocaine); the drug's own contraindications, such as a steroid over infected tissue or repeated steroid courses into a tendon at risk of rupture |
| Caution | Children (objective dosing in mA/cm²), elderly and frail patients, severe heart, kidney or liver disease, another treatment of the same area the same day (such as heat) |
Safety
The risks are those of a direct current, burns above all, plus those of the drug.
- Burns form under the electrode, more often and deeper under the cathode, where alkali forms. Keep the current density low, use buffered or well-wetted electrodes, keep contact even, and never treat skin that cannot feel.
- Drug reactions: local redness and itching, rarely allergy. Ask about allergies before every new drug.
- Wrong polarity wastes the drug and the session. Check it every time.
- Keep a record of drug, concentration, polarity, current, time and charge.
Check yourselfAnswer, then say how sure you were: a lucky guess still counts as a weak point.
1Dexamethasone sodium phosphate is to be delivered into a painful plantar fascia. Under which electrode is it placed?
2A protocol asks for an iontophoresis dose of 40 mA·min. The patient tolerates 4 mA. How long does the treatment last?
3Which property makes a drug unsuitable for classic iontophoresis?
4A 22-year-old student has severe sweating of the palms that has not responded to aluminium chloride. Which iontophoresis has the best support for this problem?
5Which finding rules out iontophoresis with a given drug but not galvanization itself?