Phonophoresis is defined as

• A. Using ultrasound to push a medication through the skin
• B. Using ultrasound to heat tissue
• C. Using ultrasound to image tissues
• D. Using ultrasound to monitor blood flow

Answer: (A)

Phonophoresis uses ultrasound to enhance transdermal drug delivery by pushing a topical medication through the skin and into underlying tissues. The ultrasound provides mechanical energy (like cavitation and microstreaming) that temporarily increases skin permeability, allowing the drug to diffuse more effectively. Heating can occur as a byproduct, but the goal is to improve drug absorption, not to image tissue or monitor blood flow. The other ultrasound applications are imaging or Doppler-based assessments, not facilitating drug delivery through the skin.