Iontophoresis, also known as electromotive drug administration (EMDA), is a remarkable technique that harnesses the power of electric current to deliver medication or other chemicals through the skin. Often referred to as “an injection without the needle,” iontophoresis has gained popularity due to its non-invasive nature and its ability to effectively administer treatment.
History of Iontophoresis
The roots of iontophoresis can be traced back to the early 1900s when its therapeutic potential was first reported. Initially, iontophoresis was used in the treatment of hyperhidrosis, a condition characterized by excessive sweating in the hands or feet. The early techniques involved the use of tap water or aluminum compounds to alleviate the symptoms of hyperhidrosis effectively.
iontophoresis has been used to accelerate wound healing using iodine, zinc or copper compounds(solan and soltani, 1986).
Route of ion transfer
Traditionally, it was believed that ions travel through the skin via pores and hair follicles. However, new research indicates that iontophoresis can actually help drugs pass through the skin by making the outermost layer, known as the stratum corneum, more permeable.
MECHANISM OF IONTOPHORESIS (BASIC PRINCIPLE OF IONTOPHORESIS):
Effective ion delivery:
Iontophoresis is a technique that uses a direct (galvanic) current to drive ions into the tissues for therapeutic purposes.
Non-invasive and safe:
This method is completely non-invasive, meaning it doesn’t require any needles or invasive procedures, making it a safe option for patients.
Low ion concentration:
Only a very low concentration of ions is needed for iontophoresis to be effective, minimizing the amount of substance required.
Ionic substances:
The substance to be delivered into the tissue needs to be ionic in nature, meaning it carries an electrical charge.
Charge matching:
The ionic substance is placed under an electrode with the same charge to facilitate movement into the tissue. The direction of movement depends on the polarity applied.
Wet pad or sponge:
A solution containing the desired drug is applied to a wet pad or sponge, which is then placed on the skin.
Electrolysis:
When a constant direct current is passed through the solution, electrolysis occurs, resulting in the production of positively charged ions and negatively charged ions.
Anode and cathode:
The positively charged chamber, known as the anode, repels positively charged chemicals into the skin. Similarly, the negatively charged chamber, called the cathode, repels negatively charged chemicals into the skin.
PHYSICS OF IONTOPHORESIS:
The following physical considerations need to be done while following iontophoresis:
⇒The amount of substance introduced;
- The basic formula for using iontophoresis to know the amount of substance introduced in grams is- I×T×ECE.
- Where I, is intensity of current in amperes,
- T, is the time in hours,
- ECE, electrochemical equivalance of the substance.
- The number of ion entering the tissues from any given area of active electrolyte is proportional to both the current density and the time of application.
⇒Ionic polarity;
- The basis of successful ion transfer lies in the physical principle: like poles repel and unlike poles attract.
- The ions being charged particles with positive or negative valences are repelled into the skin by identical charge on the electrode surface placed over it.
⇒Low level amperage;
- The lower the intensity of current, greater is the amount of penetration of the ions through the skin.
- The current is usually applied with currents up to 5mA.
- With low ionic concentration, up to 5%
- Treatment time typically in the 10 to 30 minute range
ELECTRODES:
- The electrode where the ionic solution is placed is called the active electrode, also known as the treatment or delivery electrode.
- The other electrode used to complete the circuit is commonly referred to as the dispersive, indifferent, inactive, or return electrode.
- Electrodes can be specialized pre-gelled disposable electrodes or standard metal electrodes of different types.
- Some commercial iontophoresis electrodes have specific areas to hold the drug being used, but it’s not necessary to use these electrodes.
- Therapists have traditionally used various metal or foil electrodes with damp gauze between the electrode and the skin surface to apply the treatment substance.
- It is often recommended to make the negative electrode larger than the positive electrode to minimize skin irritation. A commonly suggested ratio is that the negative (cathode) electrode should be twice the size of the positive (anode) electrode.
| Cathode | Anode |
|---|---|
| NEGATIVE electrode | POSITIVE electrode |
| Attraction of +ve ions | Attraction of -ve ions |
| Alkaline reaction by the formation of NaOH | Acid reaction by the formation of HCl |
| Increased density of proteins | Decreased density of proteins |
| Increased nerve excitability via a depolarisation effect | Decreased nerve excitability via a hyperpolarisation effect (sometimes called anode blockade) |
PHYSIOLOGICAL EFFECT OF IONTOPHORESIS
Physiological effects of iontophoresis depend on the ion(drug) selected for treatment, since each ion is different. specific ion are utilized for the treatment of specific condition and some of the effects common to all are:
1)Ion penetration:
- Normally, iontophoresis allows the drug to penetrate the skin to a depth of less than 1 mm.
- After entering the skin, the drug can be further absorbed into deeper tissues through capillary circulation and transmembrane transport.
- With iontophoresis, the drug delivery depth can range from 3 mm to 20 mm, allowing it to reach deeper target areas.
- The majority of the ions are deposited directly at the site where the active electrode is placed, ensuring localized concentration and effect.
2)Acid/Alkaline reaction:
- The anode (+) creates a weak acid reaction, similar to mild hydrochloric acid, while the cathode (-) generates a strong alkaline reaction, resembling sodium hydroxide.
- The anode has a firming effect on tissues and can act as a pain reliever, possibly because it releases oxygen locally, promoting tissue vitality.
- On the other hand, the cathode has a softening effect and releases hydrogen. It is used in clinical settings to manage scars, burns, and keloids.
3)Hyperemia:
Both the anode and cathode cause increased blood flow in the skin because they generate heat according to Joule’s law. Usually, the redness on the skin under both electrodes goes away within an hour after the treatment.
4)Dissociation:
When an electric current (direct current) is applied, substances that can produce ions in a solution break apart, releasing charged particles. These particles then move towards opposite ends or poles.
THERAPEUTIC EFFECT:
The therapeutic effects of iontophoresis depend upon the nature of the drug introduced into the tissues. the substance used in different purposes are listed in table in indication and uses of iontophoresis.
INDICATION AND USES OF IONTOPHORESIS:
| Drug / Solution | Main Indication(s) | Rationale | Parameters |
|---|---|---|---|
| Acetic Acid | Calcific tendinitis (myositis ossificans) | Acetate believed to increase solubility of calcium deposits in tendons (and other soft tissues) | 2 – 5% aqueous solution NEGATIVE pole |
| Calcium chloride | Muscle spasm (also hypersensitive peripheral nerves) | Calcium thought to stabilise excitable membranes, appears to decrease excitability threshold in peripheral nerves and skeletal muscle | 2 – 5% aqueous solution NEGATIVE pole |
| Dexamethasone | Inflammation | (synthetic) anti inflammatory | 4mg/mL aqueous solution NEGATIVE pole |
| Hydrocortisone | Inflammation | Steroid based anti inflammatory | 0.5% ointment POSITIVE pole (Rothstein et al) |
| Hydrocortisone, prednisone | Inflammation | Steroid based anti inflammatory | NEGATIVE pole (Belanger) |
| Iodine | Adhesive capsulitis Other soft tissue adhesive presentations Infection (microbial) |
Iodine acts as a broad spectrum antibiotic. Its actions in relation to adhesive presentations appear not to be fully understood | 5 – 10% solution (some use ointment) NEGATIVE pole |
| Lidocaine | Soft tissue pain Inflammation |
Local anaesthetic effects (blocks peripheral nerve activity). May stimulate healing |
4 – 5% solution (ointment) POSITIVE pole |
| Magnesium sulphate (sulfate) | Muscle spasm Myositis |
Thought that ‘relaxing’ effect is achieved by decreased excitability of muscle membrane and reduced activity at neuromuscular junction | 2% aqueous solution (ointment) POSITIVE pole |
| Hyaluronidase | Oedema (local) Subacute and Chronic stages |
Increases permeability in connective tissues thus allowing dispersion of accumulated fluid. Hydrolysation of hyaluronic acid | Delivered after reconstitution with 0.9% sodium chloride (Normasol) to give a 150µg/mL solution POSITIVE pole |
| Salicylates | Muscle and Joint pain Acute and Chronic |
Mode of action akin to Asprin – analgesia and anti inflammatory. Inhibits synthesis of prostaglandins | 2-3% sodium sallicylate solution OR 10% trolamine sallicylate ointment NEGATIVE pole |
| Tolazoline hydrochloride | Ulcers (open wounds) | Stimulates local blood flow Stimulates tissue healing (thought to be via inhibition of local vascular smooth muscle contraction) |
2% aqueous solution POSITIVE pole |
| Zinc Oxide | Open wounds – ulcers Some dermatological conditions |
Antiseptic effects related to the zinc. May stimulate healing |
20% ointment POSITIVE pole |
| Tap Water | Hyperhydrosis (illustrations below) |
Suppresses sweating in palms, soles of feet, axilla through ?keratin plug formation in ducts | Equal time with POSITIVE and NEGATIVE polarity – use 2 x hand baths. Reverse polarity 1/2 way through treatment (typically 30 minutes : 15+15) |
APPLICATION OF IONTOPHORESIS:
- Prepare the Skin: Ensure the skin is free from abrasions or cuts and wash the area with soap and water.
- Use Proper Electrodes: Avoid using dry electrodes and opt for pregelled electrodes for better contact.
- Secure Electrodes: Carefully fix the electrodes and pads to the skin to maintain proper contact.
- Correct Electrode Placement: Place the drug under the electrode with the corresponding charge (negative for negatively charged drugs like iodine, positive for positively charged ions).
- Prevent Uneven Current Distribution: Uneven current distribution can cause skin burns and irritation, so ensure proper electrode placement.
- Communicate with the Patient: Explain the procedure to the patient and instruct them to report any painful sensations immediately.
- Gradually Adjust Current: Increase the current slowly until reaching the required amount.
- Gradually Decrease Current: At the end of the treatment, slowly decrease the current before removing the electrodes.
DOSAGE OF IONTOPHORESIS:
- Treatment Time: Longer treatment times with a specific current density result in smaller ion transfer.
- Comfortable Current Densities: The current density that most people find comfortable ranges from 0.1 to 0.2mA/cm².
- Maximum Safe Current Densities: It is recommended to keep the current density under the cathode at 0.5mA/cm² and under the anode at 1.0mA/cm².
- Dosage Measurement: The iontophoresis dosage is measured in “mA min” by multiplying the total current by the treatment time.
- Pediatric Considerations: When treating children, it is advisable to start with a lower initial dose of 50-70 mA min.
- Current Intensity and Treatment Duration: To ensure safety, it is suggested to limit the total current to 5-20mA and the treatment duration to 10-30 minutes.
CONTRAINDICATION:
- Cardiac pacemaker or arrhythmia
- Unconscious patient
- Recent radiotherapy
- Carotid sinus
- Area of venous and arterial thrombosis and thrombophlebitis
- Pregnancy
- Early tendon transfer/ repair( electrical stimulation is contraindicated in the early tendon repair/ transfer, before the completion of 5th week, as the strong muscle contraction might cause a muscle or tendon damage.
- Malignancy
- Infected wound and skin lesions
- Hemorrhage
DANGERS:
- Burn
- Electric shock
- Skin irritation
- Systemic effect: just like nausea, headache, abdominal pain or mild dryness of the mouth. the patient should be warned to avoid vigorous exercise immediately after treatment and if the symptoms are severe the area of treatment should be reduced.
IONTOPHORESIS VS PHONOPHORESIS
- Iontophoresis uses electrical current to transport ions into tissues
- Phonophoresis uses acoustic energy (ultrasound) to drive molecules into tissue