Ultrasound as a potential trigger to terminate the activity of contraceptive delivery implants

In vitro and in vivo experimental results suggest the feasibility of ultrasound as a possible approach to externally affect the release rates and therefore the depletion time of implantable contraceptive delivery systems. For example poly(lactide-coglycolide) microspheres loaded with norethisterone exposed for 2 h to ultrasound at 3 W/cm² (1 MHz, 20% duty cycle) for 6 consecutive days resulted in depletion times four-fold shorter than microspheres which were not exposed to ultrasound. Scanning electron micrographs of microspheres exposed and not exposed to ultrasound revealed significant effects of ultrasound on the surface morphology of the degrading polymer.