Despite advances in pain medicine, postoperative pain control remains problematic with over 5% of patients experiencing severe pain despite standard of care pain management, and is a frequently cited reason for delayed discharge in outpatient procedures [1]. In anorectal surgeries, almost all patients experience mild-to-moderate postoperative subjective pain [2], and as an example 12% of patients report severe postoperative pain during their recovery from hemorrhoidectomy surgery [3]. Control of postoperative pain is an important goal. Preemptive analgesia is a technique that involves premedicating the patient with a regimen of medications designed to target different points in the pain cascade to prevent central and peripheral sensitization to pain, also known as "wind-up" [4]. The activation of N-methyl-D-aspartate (NMDA) receptors is an identified process that occurs in central sensitization after a noxious stimulus. By pharmacologically blocking these receptors, it may be possible to prevent or suppress the degree of central sensitization, which can prevent the hyperalgesic, or exaggerated pain response, that some patients experience [5]. Peripheral sensitization is a similar concept and occurs due to noxious stimuli in the periphery, such as a surgical incision. This type of sensitization has typically been prevented with regional anesthesia and by increasing the nociceptive threshold of the neurons with different medications.