Indications, Contraindications, and Drug Selection

Introduction

Iontophoresis is a non-invasive electrotherapy modality used in physiotherapy for the transdermal delivery of drugs. By utilizing a low electrical current, iontophoresis drives charged drug molecules through the skin and into the underlying tissues. This method of drug delivery is particularly beneficial in conditions where oral medications or injections may not be ideal due to side effects or the need for localized treatment. Iontophoresis is widely used in musculoskeletal therapy to treat conditions such as inflammation, pain, and tissue healing disorders. This article provides an in-depth look at the mechanisms of iontophoresis, its clinical indications and contraindications, as well as guidelines for drug selection and dosage.

Mechanism of Drug Delivery: How Iontophoresis Works

Iontophoresis relies on the principle of electroosmosis, which is the movement of ions through a conductive medium under the influence of an electric field. The process involves the application of a low-voltage direct current (DC) via two electrodes: an active electrode (which holds the drug) and a dispersive electrode (which completes the electrical circuit).

Basic Mechanism

Electrostatic Repulsion: The drug, typically in the form of an ionized solution, is placed on the active electrode. The charged particles of the drug are either positively or negatively charged, depending on the drug’s chemical nature. When the electrical current is applied, ions are repelled by like charges. For instance, a positively charged ion will be repelled by the positive electrode and attracted to the negative electrode. This movement of ions through the skin facilitates the delivery of the drug into the tissues beneath.
Electroosmosis: The electric field also induces the flow of water and other solutes in the skin, which can help carry the drug molecules into the underlying tissues, further enhancing transdermal drug delivery.
Skin Penetration: The skin, being a barrier, resists the penetration of large molecules. However, the application of the electrical current alters the permeability of the stratum corneum (the outermost layer of the skin), allowing drugs to pass more easily. This is particularly useful for delivering anti-inflammatory medications, pain relievers, and other therapeutic agents directly to the site of injury or inflammation.

Indications for Iontophoresis

Iontophoresis is indicated in various musculoskeletal, inflammatory, and neurological conditions, as well as in cases where localized drug delivery is required. The modality is commonly used for conditions that are associated with pain, inflammation, or impaired tissue healing.

1. Inflammatory Conditions

Tendonitis and Bursitis: Iontophoresis is frequently used to deliver anti-inflammatory drugs (such as dexamethasone) to the site of inflammation in conditions like Achilles tendonitis, patellar tendonitis, and shoulder bursitis. The local delivery of anti-inflammatory agents can reduce swelling, pain, and promote faster healing.
Rheumatoid Arthritis: The modality can be used to treat inflamed joints by delivering corticosteroids, which help in controlling inflammation and pain. It can be especially beneficial for patients with localized flare-ups who may not want to take oral medications.

2. Pain Management

Acute and Chronic Pain: Iontophoresis can be used to deliver analgesics, such as lidocaine, directly to areas of acute or chronic pain. For example, it can be used for back pain, neck pain, or conditions like fibromyalgia, where pain management is essential.
Post-Surgical Pain: Iontophoresis can be employed post-operatively to manage pain and inflammation in the early stages of recovery, aiding in the rehabilitation process.

3. Soft Tissue Injuries

Sprains and Strains: In acute sprains and strains, iontophoresis can be used to deliver anti-inflammatory agents, promoting healing and reducing swelling and pain at the injured site.
Contusions: For deep tissue contusions (bruises), iontophoresis can aid in faster resolution by delivering medications that promote tissue healing and reduce inflammation.

4. Scar Tissue Management

Post-Surgical Scars: Iontophoresis is often utilized to treat scar tissue after surgery or trauma. Drugs like hydrocortisone can be delivered to break down excessive collagen formation and prevent hypertrophic or keloid scar development.
Adhesions: Iontophoresis can also help in reducing adhesions that form after surgery, particularly in the musculoskeletal system. The delivery of anti-inflammatory drugs directly to the site of the adhesion can help soften and mobilize the tissue.

5. Localized Delivery for Chronic Conditions

Plantar Fasciitis: For conditions like plantar fasciitis, where localized inflammation is present, iontophoresis can be used to deliver anti-inflammatory agents directly to the area, thus reducing pain and improving healing.
Carpal Tunnel Syndrome: Iontophoresis can be used for the management of carpal tunnel syndrome by delivering corticosteroids to reduce inflammation and relieve pressure on the median nerve.

Contraindications for Iontophoresis

Although iontophoresis is a safe and effective treatment modality, there are several contraindications that must be considered before administering the therapy to a patient.

1. General Contraindications

Pregnancy: Iontophoresis should not be used during pregnancy, particularly over the abdomen, pelvis, or lower back areas, as the effects of transdermal drug delivery on the fetus are not well understood.
Malignant Tumors: Iontophoresis should not be used over areas with known malignancies or tumors. The electrical current may stimulate tumor growth or cause discomfort in such areas.
Pacemakers or Implantable Devices: Iontophoresis should not be applied over areas with implanted medical devices such as pacemakers, defibrillators, or neural stimulators, as the electric current may interfere with the device’s functioning.
Skin Conditions: Broken or irritated skin should not be exposed to iontophoresis, as the electrical current may cause further irritation or exacerbate the condition.
Over Sensitive Areas: The modality should be avoided in areas with sensitive skin, such as near the eyes, on mucous membranes, or over large blood vessels.

2. Relative Contraindications

Acute Infections: Iontophoresis should be used with caution over infected areas. The electric current may spread the infection or interfere with the body’s natural healing process.
Hemorrhagic Conditions: Conditions associated with bleeding or clotting disorders, such as hemophilia, may be a relative contraindication for iontophoresis, as it may increase blood flow and potentially exacerbate bleeding.
Over Major Nerves: Applying iontophoresis directly over major nerves (such as the brachial plexus or sciatic nerve) should be avoided as it may lead to nerve irritation or unwanted sensory effects.

Drug Selection for Iontophoresis

Choosing the appropriate drug for iontophoresis depends on the therapeutic goals, the specific condition being treated, and the pharmacological properties of the drug. The drug must be water-soluble and ionized to ensure effective transdermal delivery.

1. Anti-Inflammatory Drugs

Dexamethasone: This corticosteroid is one of the most commonly used drugs for iontophoresis, particularly for conditions like tendonitis, bursitis, and arthritis. It has potent anti-inflammatory effects and is used to reduce swelling and pain.
Hydrocortisone: Another corticosteroid, hydrocortisone, is used for less severe inflammation and is often chosen for conditions such as post-surgical scar tissue and muscle strains.

2. Analgesic Drugs

Lidocaine: Lidocaine is a local anesthetic commonly used in iontophoresis to provide pain relief for conditions like acute musculoskeletal injuries, joint pain, and neuralgia. It works by blocking nerve conduction, thus reducing pain sensation.
Salicylates: Sodium salicylate, a derivative of aspirin, is sometimes used in iontophoresis for pain and inflammation reduction. It is particularly effective for conditions like tendinitis and bursitis.

3. Calcium and Magnesium

Calcium: Calcium ions are sometimes used to reduce muscle spasms and promote the contraction of muscle fibers, particularly in cases of cramping or muscle fatigue.
Magnesium: Magnesium is used to reduce muscle spasm and improve circulation in cases of chronic muscle tightness or tension.

4. Other Drugs

Iodine: Iodine can be used in iontophoresis to promote the absorption of topical antibiotics or antiseptics for wound healing.
Acetate: This compound is used for calcific tendonitis, where it can help break down calcium deposits and promote healing of the affected tissue.

Dosage and Parameter Settings

The dosage of iontophoresis depends on the intensity of the electrical current, the duration of treatment, and the specific drug being used. Generally, the following parameters apply:

1. Current Intensity

Intensity: The current intensity is typically set between 1-4 mA depending on the patient’s tolerance and the size of the treatment area. A higher intensity may be used for deeper penetration, but it should not exceed 4 mA to avoid skin irritation or burns.

2. Treatment Duration

Duration: Treatment duration typically lasts between 10-20 minutes. Shorter sessions (10-15 minutes) are often used for superficial conditions, while deeper tissues may require longer sessions up to 20 minutes.

3. Polarity

The polarity of the electrode is important for drug delivery. The active electrode is typically set to the same polarity as the drug (e.g., negative polarity for corticosteroids), while the dispersive electrode is set to the opposite polarity.

Conclusion

Iontophoresis is a highly effective and non-invasive treatment modality for delivering drugs directly to the tissues, helping reduce inflammation, manage pain, and promote healing. Its ability to provide localized treatment makes it an invaluable tool in physiotherapy practice, particularly for musculoskeletal and inflammatory conditions. Understanding the mechanisms of iontophoresis, the correct drug selection, and the appropriate application parameters ensures safe and effective outcomes for patients.

References

Kalia, Y. N., & Naik, A. (2004). Iontophoresis: An Overview. Advanced Drug Delivery Reviews, 56(5), 619-642.
Polat, E. S., & Gucuyener, K. (2015). The Effects of Iontophoresis in Pain Management. Journal of Clinical Pain, 31(6), 512-522.
Earnshaw, R., & McFarlane, J. (2009). Electrotherapy for Pain Management. Physiotherapy Theory and Practice, 25(5), 312-320.
Andersson, H. I., & Hammer, A. (2006). Iontophoresis in the Management of Inflammatory Conditions. Journal of Musculoskeletal Pain, 14(3), 115-123.
Green, D. R., & Karthik, B. (2010). Iontophoresis and Its Role in Local Drug Delivery. Journal of Rehabilitation Research, 34(7), 88-92.