Disclosed are a sonotrode and its use for transdermal delivery of therapeutic or cosmetic compounds. The sonotrode 10 comprises a tubular neck 14 attached at a proximal end to a solid head 12 and ending at a distal end in a flared foot 16. When coupled to an ultrasonic transducer and applied to skin of a human or animal, the sonotrode enhances the delivery of compounds into the skin.