Iontophoresis

Original Editor '- Sai Kripa Top Contributors - Sai Kripa, Kim Jackson and Rishika Babburu

Introduction

Iontophoresis is a procedure in which an electric current will be passed through the skin which will be soaked in tap water allowing ionized or charged particles to cross the normal skin barrier. This method is considered as a non-invasive transdermal drug delivery technique based on transfer of charged molecules using low-intensity electric current.

Mechanism

There are two mechanisms that are usually involved in iontophoretic transport.

• Electro-migration
• Electro-osmosis

Electro-migration: It is also referred to as electro-repulsion. There occurs movement of ions across a membrane (the skin) under the direct influence of an electric field. There are two electrodes, cathode and anode. When an electric field is passed, the negatively charged drugs repel into the skin under the cathode whereas, the transfer of positively charged drugs happen under the anode.

Electro-osmosis: This is the second mechanism and electro-osmosis is considered as the volume flow induced by the current flow. It depends on the physiochemical properties of the molecules and the polarity of the applied current. For example- When negative charges are placed on the cathode (-), they will migrate trans dermally towards anode (+).

Points to remember-

1. Drug deliver is local but only penetrates a few mm.
2. Drug must ionize and have net charge (+ or -)
3. Negative charges are placed on the cathode (-) and they migrate transdermally to the anode (+)
4. Positive drugs are placed on the anode (+) and they migrate transdermally to the cathode.
5. The electrode in which the drug would be administered are considered as active electrode. By default, the opposite electrode would be dispersive electrode.

Parameters

Maximum Safe Current Density (MSCD)-

-Cathode | 0.5 mA/cm²

-Anode | 1.0 mA/cm²

Maximum Safe Current Intensity (MSCI)- It is calculated by multiplying the MSCD by the surface area of the electrode.

                                MSCD = MSCI/SAE

Dosage- It is given as the product of intensity and duration (D = Ma × min)

Typical dosage should be between 40 and 80 mA×min.

Procedure

There are various methods to perform iontophoresis depending upon the condition of the patient.

1. To treat hyperhidrosis- The patient sit with both hands or both feet, or one hand and one foot, immersed in shallow trays filled with tap water for a short period of time. The device will send a small electrical current through the water.  Initially, the procedure should be repeated for three times per week until the desired results are achieved. Once satisfactory dryness or result has been reached, patients are usually provided with the treatment for once per week. The treatment will take around 15 to 40 minutes depending on the machine.
2. To treat musculoskeletal conditions- In this method, transdermal drug delivery (TDD) system are mainly used. It utilizes electrical current to push ionized drugs through the skin (stratum corneum) which is typically the main barrier to drug transport. Usually analgesic or anti-inflammatory actions are applied directly into the target area. Using the rule of ‘likes repel,’ a positively charged drug is loaded into the positive side of the delivery pad or electrode and these positively charged molecules are driven through the skin by the positive current while negatively charged medications are driven in under the negative pole.

Contraindications

1. Epilepsy, Seizures
2. Pacemakers
3. Heart diseases
4. Metal implant
5. Pregnancy
6. Recent wounds, skin grafting or scar