ULTRASOUND AS A POTENTIAL TRIGGER TO TERMINATE THE ACTIVITY OF CONTRACEPTIVE DELIVERY IMPLANTS

In vitro and in vivo experimental results suggest the feasibility of u ltrasound as a possible approach to externally affect the release rate s and therefore the depletion time of implantable contraceptive delive ry 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 fou r-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 surfa ce morphology of the degrading polymer.