Iontophoresis is which of the following?

• A. A method of electrical stimulation to contract muscle
• B. A type of ultrasound therapy
• C. DC-driven transdermal drug delivery to treat inflammatory or pain conditions locally, using medications like dexamethasone or lidocaine
• D. A form of manual therapy

Answer: (C)

Iontophoresis is a transdermal drug-delivery technique that uses direct current to drive charged medication molecules through the skin to create a local anti-inflammatory or analgesic effect. By applying a DC field, ionized drugs such as dexamethasone or lidocaine are pushed into underlying tissues, targeting the affected area with minimal systemic exposure. This approach is different from modalities that physically stimulate tissue or provide mechanical therapy: it does not aim to contract muscles, deliver ultrasound energy, or involve hands-on manual techniques. Instead, it uses electrical current to deliver a medication right where it’s needed, which is why it’s used for localized inflammation or pain.