Compositions and methods for administration of local anesthetics that are delivered by a single injection and enable repeated on-demand or high influx analgesia over extended periods have been developed. Pharmaceutical compositions including an effective amount of one or more sodium channel blockers including site 1 sodium channel blockers, optionally one or more alpha-2-adrenergic agonists, which are optionally encapsulated in liposomes, particles or microbubbles, and one or more triggerable elements are provided. The triggerable elements allow delivery of the encapsulated anesthetic drugs when an appropriate triggering stimuli are applied. Exemplary triggering agents or stimuli include near-infrared irradiation, UV- and visible light, ultrasound and magnetic field. In one embodiment, ultrasound is used to trigger a burst of microbubbles to enhance penetration of local anesthetic.
