Iontophoresis Definition .
Iontophoresis is a therapeutic technique, which involves the introduction of ions into the body tissue through the patient’s skin. The basic principle is to place the ion under an electrode with the same charge, i.e. negative ion placed under cathode and positive ion placed under anode. This technique is also known as ‘technique of ion transfer’ into the body tissues by using electrical current as a driving force (LeDuc, 1903).
The electrode under which ions are placed, is therefore called ‘active electrode’. A constant direct current is used for propelling the ions into the patient’s body tissues. Direct current ensures unidirectional flow of ions that is why only direct current is used and alternative current cannot be used. Iontophoresis has several advantages therapeutically such as being painless, sterile and noninvasive method to introduce specific ions into the body tissues.
The common disadvantage associated with iontophoresis is chemical burn that usually occurs as a result of direct current itself and not because of the ion being used in the treatment. The quantity of the ions transferred into the tissues through iontophoresis is determined by the intensity of the current or current density at the active electrode, the duration of current flow and the concentration of ions at the active electrode or in the solution.
It is also known as ion transfer, ionization or cataphoric medication (memorize these names with synonym ICI). It is believed that Stephane Leduc discovered it in 1903. Iontophoresis is the specific transfer of ions into the body tissue by the use of direct current for therapeutic purpose .
Principle of Iontophoresis .
It is based on the principle that an electrically charged electrode will repel a similarly charged ion. In other words, if a drug is in ionic form, then it can be made to travel through the body tissue through the skin by the use of direct current via repulsive force between similar charges. Two rabbits are arranged in a series. Over positive electrode of rabbit A, strychnine is applied.
Over negative electrode of rabbit B, potassium cyanide is applied. Other electrodes are moistened in order to allow the passage of current. Pass direct current through this series. Rabbit B will die and rabbit A will have convulsions. Place new rabbits and reverse the polarity, there will be no effect. This suggests that there is a transfer of ions when placed over similarly charged electrodes.
Effectiveness .
Effectiveness of iontophoresis depends on number of ions transferred and depth of penetration. Number of ions transferred is determined by current density, duration of current flow and concentration of ions. Iontophoresis is facilitated by increased vasodilation to the area under electrodes and inhibited by insoluble nature of ions.
Method of Application .
1. Assessment of Patient .
When you have decided to go for iontophoresis then inquire about allergy to any drug, inspect the area of the body where iontophoresis is to be done and check the sensation.
2. Selection of ion .
Select the chemical solution containing the desired ions with adequate concentration. For example, if you want an analgesic effect then select salicylic acid as a solution since it contains salicylate ions which has analgesic properties.
3. Procedure .
Explain the procedure to your patient so that he is aware about what you are going to do and cooperate with you.
4. Position of Patient .
Position your patient in such a way that he is comfortable during the treatment. I prefer mostly supine.
5. Clean the area to be treated .
Clean the area of body to be treated with spirit or normal saline and cotton swab. It reduces skin resistance and removes the dust particles from the area and thus facilitates iontophoresis.
6. Preparation of electrodes and placement.
Moisten or soak the piece of bath towel/lint cloth in the drug solution and place it over active electrode and now place the active electrode over the body part to be treated or massage the solution into the skin and place the active electrode over it. Place the larger indifferent electrode at least 18 inches away from the active electrode. Secure the electrodes in position with velcro straps.
7. Application of treatment .
Connect the electrodes to desired terminals. Increase the intensity until prickling, tingling or burning sensation is produced or 0.1 to 0.5 mA/cm² of electrode. Continue the treatment for 15 minutes and check the undersurface of electrodes after every five minutes so as to prevent electrochemical burn.
8. Termination of the treatment .
After 15minutes, reduce intensity gradually and remove the electrodes.
Commonly used Positive ions and their indications .
1. Hydrocortisone: Used for its anti-inflammatory effects in conditions like rheumatoid arthritis, tendinitis, bursitis, etc.
2. Calcium chloride: Calcium ions are used. It is found effective in stiff joint and posttraumatic pains.
3. Zinc oxide: Used in cases of ulcers and open lesions, has property of healing.
4. Magnesium oxide: Used in arthritis, is an excellent muscle relaxant, good vasodilator and mild analgesic.
5. Dexamethasone: Used for treating musculoskeletal inflammatory conditions.
Commonly used Negative ions and their indications .
1. Iodine: It is an effective sclerolytic agent, an excellent bacteriocidal and a fair vasodilator. Effectively use for adherent scars, adhesive capsulitis.
2. Chlorine: Also an effective sclerolytic agent, useful for scar tissue, keloides and burns.
3. Salicylic acid: A general decongestant, sclerolytic and anti-inflammatory agent.
4. Sodium or potassium citrate—Effective in rheumatoid arthritis.
Uses of Iontophoresis .
Iontophoresis is commonly used for arthritic and myalgic pain, softening of the scar tissues and adhesions, gouty and calcium deposits, bursitis and tendonitis, hyperhydrosis, wounds and ulcer healing and allergic rhinitis. For relief of pain and muscle spasm in cases of myalgia, arthritis and sprain, sodium salicylic acid can be used.
In order to soften scar tissue and adhesions, a solution of sodium chloride can be used. Gouty deposits or calcium deposits can be treated with acetic acid iontophoresis. Inflammatory conditions such as bursitis, tendonitis, etc. can be treated with hydrocortisone iontophoresis. Hyperhydrosis, which is characterized by excessive sweating, can be treated with hyaluronidase iontophoresis.
For the acceleration of wound and ulcer healing, iontophoresis can be done with an adequate concentration (preferably 5%) of zinc sulfate. Also, zinc sulfate can be used to reduce infections such as Athlete’s foot, tinea pedia and in the treatment of allergic rhinitis. Histamine iontophoresis is used to increase blood supply.
Contraindications and Dangers .
Various contraindications for iontophoresis are, hypersensitivity, impaired sensation and pregnancy. (You can remember the contraindications with mnemonic ‘HIP’ where H stands for hypersensitivity; I stands for impaired sensation and P for pregnancy.) Dangers of iontophoresis are chemical burns, alarming shock, electric shock and headache.
Chemical burn or tissue destruction is likely to occur if the current density is high, metal electrode touches the skin directly because of insufficient padding. Shock may occur if patient touches the live part of the circuit, from which direct current is produced or if the insulation of the main cable is defective.
Alarming shock is likely to occur if circuit is broken suddenly. It may occur if electrodes are not moistened enough or when wrinkles are present or when air gaps are present between electrodes and body tissue. Blood pressure changes/ headache may occur in case of histamine iontophoresis.
