Which statement correctly describes phonophoresis in relation to ultrasound?

• A. Phonophoresis relies on electrical currents to drive medication
• B. Phonophoresis uses magnetic fields to deliver drugs
• C. Ultrasound enhances transdermal drug delivery by driving the drug through the skin
• D. Phonophoresis reduces the effectiveness of medications

Answer: (C)

Phonophoresis uses ultrasound energy to enhance delivery of a medication through the skin. The ultrasound provides mechanical effects—like cavitation and acoustic streaming—that disrupt the skin’s barrier and increase permeability, allowing the drug to diffuse more readily into underlying tissues. That’s why the statement describing ultrasound as enhancing transdermal drug delivery by pushing the drug through the skin is the best fit. It’s different from iontophoresis, which relies on electrical currents to drive charged drugs, and from magnetophoresis, which would use magnetic fields. It also doesn’t imply a reduction in effectiveness; when applied correctly with the right coupling medium and formulation, phonophoresis can improve drug absorption through the skin.