 A computer-generated algorithm will be used to randomize patients in a 1:1 allocation into the intervention or control group during surgery. Randomization will be stratified by laterality of the reconstruction i.e. bi- or unilateral because this could affect participant pain levels. Randomization will be managed and maintained by a third party service, not otherwise involved in the study, in the hospital pharmacy department. Allocation methods will not be disclosed to study investigators. Following randomization, the study drug will be sent to the main operating theatre, and given at the conclusion of the surgery. Both the intervention and control drug will be of the same storage and opacity to prevent identification by the patient or care providers. From there, the patient will then be administered the same drug according to the randomization result, based on delivery by the third party pharmacy service. 