Abstract: Compositions and methods of use related to formulations comprising anesthetics are generally described. Some embodiments are directed to compositions comprising a plurality of micelles and/or particles, and an anesthetic contained internally. These can be used to control and/or prolong the duration of IVRA while reducing the risk of systemic toxicity commonly due to administering anesthetics. The control and/or prolonged duration of IVRA may be due, at least in part, to the attachment of the sufficiently small micelles and/or particles to a biointerface (e.g., blood vessel surface) where the composition has been administered. Conventional IVRA methods commonly do not utilize potent and long-acting anesthetics (e.g., bupivacaine) due to the risks of cardiac toxicity. The compositions and methods described herein, however, provide a pathway for increased safety and efficiency of the use of such anesthetics, in certain embodiments. Resultantly, the performance (e.g.