Transdermal Delivery of Enfuvirtide in a Porcine Model Using a Low-Frequency, Low-Power Ultrasound Transducer Patch.

Ultrasound-mediated transdermal delivery is a promising parenteral administration method for large-molecule or unstable medications. This study evaluated skin health and systemic delivery when administering enfuvirtide, an injectable anti-retroviral medication, over a 1-mo period in a porcine model using a low-frequency cymbal transducer. Three groups received twice-daily treatments: (i) enfuvirtide injection control (n = 12); (ii) saline ultrasound control (n = 6); and (iii) enfuvirtide ultrasound treatment (n = 13). Ultrasound parameters were as follows: 30-min exposure, 90 mW/cm², 24-26 kHz and 15% duty cycle. No statistical difference in trans-epidermal water loss, a measure of skin health and function, was seen between ultrasound-treated and control skin sites for either saline (p = 0.50) or enfuvirtide (p = 0.29) groups. Average trough plasma concentrations of enfuvirtide were 0.6 ± 0.2 and 2.8 ± 0.8 μg/mL for ultrasound and injection, respectively. Tolerability and efficacy results indicate that chronic, low-frequency ultrasound exposure can be a practical means for transdermal delivery of medications such as enfuvirtide.