How does phonophoresis relate to ultrasound?

• A. It uses electrical stimulation to drive medications
• B. It is a heating technique
• C. Ultrasound enhances transdermal drug delivery by driving the drug through the skin
• D. It reduces skin permeability to drugs

Answer: (C)

Phonophoresis uses ultrasound to push topical medications through the skin by increasing its permeability. The ultrasound energy produces mechanical effects in the skin—such as cavitation and acoustic streaming—that disrupt the lipid barrier of the outer skin layer and create convective currents. This makes it easier for drug molecules to diffuse into deeper tissues. Heating can occur as a byproduct, but the key idea is that ultrasound facilitates transdermal drug delivery, not by electrical stimulation or by simply heating. It’s about driving the drug through the skin with the mechanical effects of ultrasound.