Which modality uses direct current to deliver ions across the skin?

• A. Direct current iontophoresis
• B. HVPC
• C. Pulsed electrical stimulation
• D. NMES

Answer: (A)

Direct current iontophoresis uses direct current to push charged ions through the skin by electrophoresis. The medication is placed under the active electrode, and the sustained DC creates a constant electric gradient that drives the ion from the electrode into underlying tissues. This is what allows ions to cross the skin barrier.

The other modalities deliver current primarily to stimulate nerves or muscles, or use pulses and high voltage rather than a continuous direct current, so they are not designed to transport ions across the skin.