Ultrasound mediated drug delivery—A new era using ultrasound contrast agents?

Abstract

Ultrasound has been used therapeutically for decades. High energy ultrasound is used clinically in hyperthermia. Transdermal drug delivery is accomplished with ultrasound, perhaps more effectively at low frequencies because of more efficient cavitation. High intensity focused ultrasound (HIFU) is used to coagulate tissue for treatment of cancer and hemostasis. Recently, contrast agents have been developed for diagnostic ultrasound. These agents can also be used as exogenous cavitation nuclei for therapy. Compared to some of the other therapeutic ultrasound techniques, exogenous cavitation nuclei may enable use of lower power levels. Applications of ultrasound contrast agents as cavitation nuclei include sonothrombolysis and drug and gene delivery. Cavitation of contrast agents can be used to increase capillary permeability to deliver drugs. Co-administration of ultrasound contrast agents with transdermal ultrasound accomplishes sonothrombolysis. Acoustically active carriers (contrast agents) have been developed to carry drugs and genes; systemic administration produces local drug delivery within the field of insonation. Contrast agents may open a new era of therapeutic applications of ultrasound for drug delivery and sonothrombolysis.