The term Iontophoresis is simply defined as ion transfer( ionto=ion; phoresis=transfer). iontophoresis, also called electromotive drug administration(EMDA), is a technique which uses an electric current to deliver a medicine or other chemical through the skin. it is sometimes called ” an injection without the needle”.
The use of iontophoresis was first reported in the early 1900s. historical uses of iontophoresis include use of tap water or an aluminum compound to treat hyperhidrosis of hand or feet. iontophoresis has been used to accelerate wound healing using iodine, zinc or copper compounds(solan and soltani, 1986).
It is a non-invasive, specialized technique of electrical stimulation that uses eletrical polarity of continuous direct current to ionize medicines placed beneath surface electrodes and transfer them into the body through the skin.
Route of ion transfer
The primary route of ion transport across the skin is thought to be through the skin pores and the hair follicles. however more recent studies suggest that, iontophoresis may promote transdermal drug penetration, primarily by increasing the permeability of the stratum corneum, the main barrier to transdermal drug uptake.
MECHANISM OF IONTOPHORESIS( BASIC PRINCIPLE OF IONTOPHORESIS): The positively charged chamber, called the anode, will repel a positively charged chemical into the skin. The negatively charged chamber, called the cathode, will repel a negatively charged chemical into the skin. PHYSICS OF IONTOPHORESIS: The following physical considerations need to be done while following iontophoresis: ⇒The amount of substance introduced; ⇒Ionic polarity; ⇒Low level amperage; < p class=”green h3″>ELECTRODES: The electrode under which the ionic solution is placed is called the ACTIVE electrode (other terms include TREATMENT electrode or DELIVERY electrode). The other electrode, which is used to complete the circuit is most commonly called the DISPERSIVE, INDIFFERENT, INACTIVE or RETURN electrode. The electrodes can be special pre gelled disposable electrodes or standard metal electrodes of various types. Some commercial iontophoresis electrodes have special wells or receptacle areas for the drug in question. It is not necessary to use these (commercial) electrodes, and for many years, therapists have used various metal / foil electrodes with the substance needed for the treatment applied to the wet/damp gauze between the metal electrode and the skin surface. It has been suggested that commonly, the NEGATIVE electrode is made larger (relative to the positive electrode) to avoid skin irritation (whether the ionic driving electrode or not). Figures often cited suggest that the negative (cathode) electrode should be 2 x larger than the positive (anode) electrode. Anodal and Cathodal Reactions in response to Iontophoresis 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: 2)Acid/Alkaline reaction: 3)Hyperemia: 4)Dissociation: < p class=”green h3″>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: Acetic Acid Calcific tendinitis (myositis ossificans) Acetate believed to increase solubility of calcium deposits in tendons (and other soft tissues) 2 – 5% aqueous solution 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 Dexamethasone Inflammation (synthetic) anti inflammatory 4mg/mL aqueous solution 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 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) Lidocaine Soft tissue pain Local anaesthetic effects (blocks peripheral nerve activity). 4 – 5% solution (ointment) Magnesium sulphate (sulfate) Muscle spasm Thought that ‘relaxing’ effect is achieved by decreased excitability of muscle membrane and reduced activity at neuromuscular junction 2% aqueous solution (ointment) Hyaluronidase Oedema (local) 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 Salicylates Muscle and Joint pain Mode of action akin to Asprin – analgesia and anti inflammatory. Inhibits synthesis of prostaglandins 2-3% sodium sallicylate solution Tolazoline hydrochloride Ulcers (open wounds) Stimulates local blood flow 2% aqueous solution Zinc Oxide Open wounds – ulcers Antiseptic effects related to the zinc. 20% ointment Tap Water Hyperhydrosis 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: DOSAGE OF IONTOPHORESIS: CONTRAINDICATION: DANGERS: IONTOPHORESIS VS PHONOPHORESIS
Examples of commercialliy available iontophoresis electrode systems
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)
Drug / Solution
Main Indication(s)
Rationale
Parameters
NEGATIVE pole
NEGATIVE pole
NEGATIVE pole
Other soft tissue adhesive presentations
Infection (microbial)
NEGATIVE pole
Inflammation
May stimulate healing
POSITIVE pole
Myositis
POSITIVE pole
Subacute and Chronic stages
POSITIVE pole
Acute and Chronic
OR
10% trolamine sallicylate ointment
NEGATIVE pole
Stimulates tissue healing (thought to be via inhibition of local vascular smooth muscle contraction)
POSITIVE pole
Some dermatological conditions
May stimulate healing
POSITIVE pole
(illustrations below)