2022 Iontophoresis

Therapeutic
Technologies for
Occupational Therapy

Iontophoresis

In order to prepare for the module on iontophoresis, please read the
corresponding chapter in Physical Agent Modalities: Theory and
Application fo r the Occupational Therapist, by Alfred G. Bracciano.

Learning Objectives

• Describe the clinical applications for iontophoresis
• Discuss the biophysiology and mechanism related to transdermal delivery of

medication
• Identify common medications used in iontophoresis and their pharmacology
• Outline clinical decision-making regarding iontophoresis, indications and

precautions

Iontophoresis: Ion Transfer

• Iontophoresis is a method of
topically delivering medication
or ionized drugs into a localized
area of tissue by using direct
electrical current to create a
therapeutic effect.
o Iontophoresis has been
increasingly used as an
alternative to oral or
parenteral (needle injection) delivery of medication.

• Iontophoresis is a non-invasive, non-traumatic, essentially painless method of drug
delivery to a specific tissue.

• Iontophoresis is frequently used in rehabilitation, dentistry, dermatology, and
oncology.

• Iontophoresis is considered an active transdermal method of drug delivery, using
direct current to ionize the medication.

History

Iontophoresis was first used as a method of delivering ionic medications into tissues in
the late 1800’s. Leduc identified the concept of iontophoresis and ion transfer by
applying electricity in 1908.
As technology has advanced, the effectiveness of electrodes and equipment has
dramatically improved. Prior to the advancements in equipment and electrodes, there was
a risk of burns and patient discomfort.
There are now hundreds of papers on iontophoresis drug delivery for a variety of
conditions and medications, though many of them are not controlled studies.

Iontophoresis versus Phonophoresis

Both techniques deliver chemicals to biologic tissues.
• Phonophoresis uses acoustic energy through ultrasound to drive
molecules into tissues.
• Iontophoresis uses electrical current to transport ions into tissues.

Current Iontophoresis Use

Iontophoresis use is growing rapidly as the technology has improved.
• Properly applied, iontophoresis is virtually painless and can be an effective alternative

to injections or orally administered drugs.

Medication can also be delivered directly to the treatment site without the complications
or disadvantages of parenteral delivery.
The quantity of medication delivered to the targeted tissue is also more controlled and
remains relatively consistent between treatments. The risk of infection due to injections
is eliminated and side effects of the treatment are minimal.

Patients should always be questioned as to any known drug allergies and clinicians
should be aware of drug interactions. However, the most common side effect is transient
skin irritation which is caused by the direct current and the biophysiological changes
which occur under the active (medicated) electrode.

Components of an Iontophoretic System

Four basic components:
• Power source for generating controlled direct current
• Drug containment and dispersive electrodes
• Medication(s)
• Skin

Three of the four basic components are well known and controlled
• Skin of patient is considered an unknown variable

Biophysiology

• Transdermal delivery used with various medications
• Skin has certain characteristics and permeability
• Skin acts as barrier
• Iontophoresis uses small levels of electrical current

Iontophoresis and transdermal drug delivery is widely used to introduce various
medications into selected tissue through the outer layer of the body, the skin.

Because of certain characteristics of the skin and its permeability, not all medications
can be administered transdermally. The skin acts as a barrier, allowing very few drugs
or chemicals through the skin. To overcome this barrier, iontophoresis using small
levels of electrical current are used to facilitate the movement of the drugs into the
tissue.

Skin

The skin is composed of three layers and is 3 to 5 mm thick.
It consists of the epidermis, dermis, and hypodermis.

The primary block to penetration of medications through the skin is the stratum
corneum.

• The stratum corneum is the lipid rich outer most layer of the epidermis.
• When the medication is able to penetrate this barrier, it becomes able to passively

diffuse in the underlying subcutaneous tissue layers.

Mechanism

There are two primary methods that allow the drug to penetrate the underlying tissue:
• movement between the intercellular matrix, and
• through the normal skin openings.

The skin is permeable to lipophilic or lipid soluble chemicals and acts as a barrier to
water soluble or hydrophilic substances.

• This lipid layer acts like the “mortar” between bricks.
• Small lipophilic molecules can pass through this intercellular matrix.

Normally occurring skin openings such as the hair follicles, sweat, and sebaceous glands
also provide an entrance extending through the epidermis into the deeper dermal layer.

• These structures are more permeable and proximal to the vascular supply, so
applying direct current to the skin facilitates the movement of chemicals into the
subcutaneous tissue.

Basic Principles of Ion Movement

The outer layer of the epidermis, the stratum corneum, is composed of cells called
corneocytes, which are separated by free fatty acids creating a lipid environment.
• The stratum corneum is an effective barrier to water and other ionic substances,
keeping water within the body and preventing foreign material from entering.

In iontophoresis, the direct electrical current moves the ions in a particular direction
based on the principle that like charges repel and opposite charges attract.

• The charged, medicated drugs are repulsed by an electrode of the same charge.
• This is similar in concept to taking two magnets and placing the same end together

(positive:positive or negative:negative).
▪ The ends of the magnet will push the like charged end of the magnet away.

Basic Principles of Ion Movement

Ions possessing positive charges can be moved into the epidermis by positive electrode
and negatively charged ions are propelled by the negative electrode.

• Negatively charged electrodes are known as the cathode,
• Positively charged electrode known as the anode.

When electrical current is applied to the electrodes, it repels the ions away from the
common pole toward the opposite pole facilitating movement of the ions into the
underlying tissue.

• The delivery or medicated electrode is placed at the target tissue and a larger
dispersive electrode is placed elsewhere, removed from the target area.

• The ions are repelled from the electrode with the same charge and attracted to the
oppositely charged electrode.

• The medication, dissolved in water or a water soluble gel, is placed on or under the
deliver electrode and the patient’s skin.

• When the polarity of the medicated electrode is the same as that of the ion to be
delivered, the ion penetrates the local subcutaneous tissues and superficial muscles
and enters the systemic circulation.

• Once the medication molecules cross the stratum corneum, the drug is dispersed to
all local tissue, with the highest concentration occurring in the tissues closest to the
treatment (electrode) site.

Effectiveness

Effectiveness of iontophoresis is dependent on the number of ions transferred, the
depth of penetration, the combining of ions chemically with other substances in the
skin, and the ability of the individual ion to enter the body.

• Ion penetration extends approximately 10 mm below the electrode surface, though
the chemical effects from the medication will extend to deeper levels through
capillary action and the biophysical conductance of the current.

Delivery of medication directly to a particular target tissue will not likely be effective
with a small, localized, superficial target treatment area.

Other factors which affect the efficacy of iontophoresis include
• skin integrity at the treatment site,
• the polarity of the treatment electrode and the drug ion,
• the pH and concentration of the drug solution,
• competing ions in the solution,
• the application of other treatments, and
• the electrical stimulation parameters used.

Skin Integrity

Alterations in skin integrity at the targeted treatment area can alter drug penetration.

Skin damage also affects electrical impedance and increases the risk of burns and patient
discomfort.

• Acids and bases also form at the electrodes and may affect the ability to deliver the
medication due to changes in the pH of the medicated solution.

Physiological effects also occur under the electrodes which affect the effectiveness.
• At the negative pole, there is the attraction of positive ions, an alkaline reaction
occurs, resulting in the formation of bases.
• This reaction is more irritating to the skin than the acidic reaction which occurs at
the anode.

Because DC is continuous, it allows ions to accumulate at electrodes which further
exacerbates the potential for electrochemical skin irritation and burns under the negative
electrode.

• Iontophoresis should not be applied over skin which has damage such as scratches,
cuts, lacerations or abrasions.

• Clinicians should use lower levels of electrical current when the cathode is the
treatment electrode, than when the anode is used.

Medication Concentration

Medication concentration also may affect delivery and effectiveness.
Low concentrations of medication have been demonstrated to be successful for
treatment, and higher concentrations are not necessarily more effective. This may
be due, in part, to higher interionic attraction at higher concentrations which retard
the delivery of the medication.
• The use of lidocaine (positively charged analgesic) and dexamethasone (negatively
charged anti-inflammatory corticosteroid) are frequently applied in the clinic
simultaneously using iontophoresis.

However, using two medications simultaneously is also controversial.
• If the ions possess the same charge, there will be a greater concentration of this

charge at the electrode delivery site, and both types of ions will compete for the
current, which may decrease the amount of either or both medications being
delivered.
• If oppositely charged, the ions may be electrostatically attracted to each other,
allowing the oppositely charged medication to the delivery electrode to
“piggyback” into the body.

We recommended that only one medication be administered from the treatment
electrode, and that the medication and the treatment electrode possess the same polarity.

Application of Other Physical Agents

Other physical agents are often applied prior to or after iontophoresis treatments with the
goal of enhancing the delivery of the medication or the improving the efficacy of
treatment.

Use of hot packs, ultrasound, or heating the tissue prior to or after iontophoresis may be
counterproductive, as these interventions may increase the blood flow in the targeted
area and accelerate the removal of the medication from the region.

The clinician should be cognizant of the stage of healing and consideration of the
problem being treated before applying any physical agent.

Using a thermal agent during the acute inflammatory stage of recovery would be
inappropriate to use, even when pairing the treatment with iontophoresis using an anti-
inflammatory.

Dosage

Dosage is measured in milliamp-minutes: the milliamps of the current multiplied by the
minutes, or length of treatment.

There are two primary variables affecting the number of ions transported to the tissue, the
current amplitude, and the duration of the current flow.

• It is not the volume of the fluid or medication which is being delivered to the
underlying tissue, but the ions which are being transported.

• The amount of drug delivered to the tissue is determined by the current and the
duration of the treatment (current x time).

• The volume of medication will not affect the amount of ions delivered, assuming it
is of the same concentration.

The significant variables affecting dosage are the current and duration.

⚫ Dosage is measured in milliamp-minutes
⚫ Two primary variables affect number of ions transported to the tissue:
⚫ the current amplitude, and
⚫ the duration of the current flow.
⚫ Dosage (mA/min) = Current (mA) x Treatment time (min)
⚫ Examples:
▪ 40 mA/min = 4.0 mA (current) x 10 min (time)
▪ 40 mA/min = 2.0 mA (current) x 20 min (time)
▪ 24 mA/min = 2.0 mA (current) x 12 min (time)

Amplitude

The current density determines if a small, safe, and comfortable amount of current is
being applied, not the overall total current.

• Most commercial units deliver a maximum current of 4 mA.

Current density is dependent on the surface area of the electrode and is determined by
dividing the current amplitude by the total area of the electrode.

• Lower current density should be used to prevent skin irritation or burning.

Clinical parameters should be based on client tolerance and comfort rather than the speed
or rapidity with which the treatment can be administered.

Treatment Duration

Treatment time, duration, and on time are the same with DC for iontophoresis; as the
current is on continuously until the treatment is completed.

Dosage is recommended to be within the range of 40-80 mA minutes. Treatment times
can be between 10 to 40 minutes.

Within the recommended dosage range, there are a variety of possible combinations of
current amplitude levels and treatment times, which are dependent on patient tolerance
and treatment efficacy.

There are no hard-and-fast rules related to optimal treatment dosages and combinations of
current amplitude and clinicians should consider patient comfort and tolerance of the
current.

Indications

Iontophoresis can be an effective method of intervention applied to a variety of
conditions treated by occupational therapists. Most often, iontophoresis is clinically used
in the treatment of inflammatory conditions.

There are a number of other diagnoses and interventions for which iontophoresis is
effective including local anesthesia to decrease joint pain and inflammation, and for
musculoskeletal inflammatory conditions.

Conditions most often treated by occupational therapists and which respond positively to
the medications include: carpal tunnel syndrome, epicondylitis, ulnar nerve inflammation,
elbow strain/sprain, radiohumeral bursitis, triceps tendonitis, gleno-humeral bursitis, hand
and wrist tendinitis/tenosynovitis, and DeQuervain’s disease.

• Treatment parameters should always be patient specific and the therapist should
have a strong understanding of the pathophysiology of the disease and the
medications being used.

Some manufacturers protocols have been developed, but the clinician should use caution
as many reports and protocols lack structured research review and are more anecdotal.

Medications

There are a wide variety of prescription medications and non- prescription substances
which can be delivered using iontophoresis.
Most commonly used medications with iontophoresis are water- soluble corticosteroids
and local anesthetics.

Drugs used for iontophoresis must be water-soluble and ionized.
Any medications used for iontophoresis should be manufactured to the standards
established in the US Pharmacopoeia as they will contain the correct stabilizers and
preservatives insuring potency and stability until the drug’s expiration date.

• All medication should be discarded by the expiration date on the label.
Other commonly used medications include Lidocaine which is used for its anesthetic
effect and sodium salicylate can be used for decreasing edema.

With any medications used in iontophoresis, the therapist should be knowledgeable about
the pharmacology, drug interactions, and contraindications of the medication to be used.

• Any questions regarding the therapeutic regimen or use of medication should be
discussed with the physician or pharmacist before use.

• Clinically, a physician’s prescription for iontophoresis specifying the medication to
be used should always be obtained before administering the treatment.

Case Study: Iontophoresis

LP is a 65 year old female diagnosed with shoulder impingement syndrome of the left
shoulder. She reports that the pain began approximately 6 weeks ago after “trimming her
shrubs”. The pain has decreased since that time, but her shoulder has gradually become
more stiff and she is more guarded in her movements. She reports pain when she lifts her
arm to brush her hair or to complete any overhead activities or when attempting to lift
heavy packages or items. The objective evaluation is significant for guarding of the
upper extremity and decreased range of motion. The patient displays full active range of
motion in the right upper extremity, but displays 140 degrees of flexion and abduction in
the left. Passive range of motion for internal rotation is 60 degrees, external rotation is 45
degrees with pain. The patient reports pain in the anterior compartment of the left
shoulder with palpation and in an arc of movement of the left shoulder. Muscle strength
is decreased secondary to pain.

Analysis of Clinical Findings

The patient presents with impairment of movement in the left upper extremity at the
shoulder, with both passive and active motion. This has resulted in decreased ability to
perform activities of daily living. The patient’s signs and symptoms, and the relatively
short duration of her problem, indicate that the condition may possibly have progressed to
the fibroplasia stage of healing, though there is the possibility of inflammation. She does
report pain in the anterior compartment of the left shoulder. She guards the upper
extremity.

Goals of Treatment

Proposed goals of treatment are to improve normal active and passive pain-free motion of
the left shoulder and to facilitate LP to perform all activities of daily living using both
upper extremities. The patient presents with a subacromial impingement syndrome. Since

her shoulder range of motion is likely restricted by soft tissue shortening and
inflammation of the subacromial-sub deltoid bursa, joint capsule, and the tendon of the
long head of the biceps, the treatment should be directed at increasing the extensibility
and length of the shortened tissue and decreasing the inflammatory process. Strength
should be reevaluated as the patient regains range of motion as she may have strength
deficits at the end ranges due to disuse. If the patient does have strength deficits, an
additional goal of treatment would be to restore normal strength to the left shoulder
muscles.

Determination of Appropriateness of Iontophoresis

There are a number of approaches which could be used with this patient. Thermotherapy
would be appropriate physical agent to use to increase soft tissue extensibility and to
promote circulation. Due to the inflammatory process of the subacromial bursa,
iontophoresis using dexamethasone (a corticosteroid/negative ionic prep) would be an
appropriate first step in the treatment. (Tx: 80mAmin of dexamethasone, 3 times per
week until pain resolves).
As the pain decreases and range of
motion increases, iontophoresis
could be discontinued, and
ultrasound applied. Thermal
ultrasound applied after a series of
iontophoresis would be applied to
increase capsular extensibility,
with the joint capsule being
stretched during and/or
immediately after the application
of this agent.