The 2020 guideline from the American Society for Gastrointestinal Endoscopy and the 2021 guideline from the American Society of Colon and Rectal surgeons provide a comprehensive review on management of acute colonic pseudo-obstruction (ACPO) and colonic volvulus. Traditionally administered intravenously in bolus doses for ACPO, neostigmine has also demonstrated success through alternative administration routes. A 2018 multicenter, retrospective, observational study involving 182 patients with ileus, ACPO, or refractory constipation showed that subcutaneous administration of neostigmine led to stool passage within a median time of 29 hours (Table 1). Therefore the panel suggests that for patients with ACPO who do not respond to bolus dosing of neostigmine, it is suggested to consider alternative methods of administering neostigmine. These alternatives include subcutaneous administration or continuous intravenous infusion. Although the panel does not provide route-specific recommendations for subcutaneous administration and does not call for ICU-level monitoring, both guidelines emphasize that neostigmine should be given in a setting equipped for cardiopulmonary monitoring and rapid intervention. Continuous cardiac-rhythm and respiratory monitoring are required, and glycopyrrolate or atropine must be readily available to manage bronchospasm or bradycardia should they occur. [1], [2]
A 2024 review article explored the intravenous and subcutaneous administration of neostigmine for ACPO, also known as Ogilvie’s Syndrome, emphasizing safety and efficacy in patients. A particularly noteworthy feature of the condition is the acute dilation of the colon without anatomical obstruction, primarily affecting elderly males who have undergone surgical procedures. Neostigmine, an acetylcholinesterase inhibitor, has become an essential pharmacological intervention when conservative treatments fail. Historically, intravenous neostigmine has been the preferred method due to its rapid action and pronounced efficacy, though it necessitates intensive cardiac monitoring due to potential adverse events such as bradycardia (5-12% across studies). The review highlighted emerging clinical acceptance of subcutaneous neostigmine, which offers a more gradual absorption, reducing the intensity of cardiovascular complications and requiring less monitoring. Comparative analysis across multiple studies on intravenous and subcutaneous neostigmine administration revealed distinct differences in response times and adverse events. For instance, findings from a 2018 multicenter, retrospective study showed subcutaneous neostigmine having a median time to first bowel movement of 29.19 hours, compared with minutes to hours for intravenous dosing, albeit with a minimal incidence of bradycardia. In contrast, a 1999 prospective, double-blind trial demonstrated a median response time of four minutes for intravenous neostigmine, however, this was accompanied by a higher rate of bradycardia. Despite the absence of direct randomized controlled trials comparing the two routes, current evidence supports that both forms have legitimate clinical applications based on patient-specific factors, urgency, and facility capabilities. However, the article underscores the necessity for prospective studies to further define optimal administration protocols and dosage guidelines, especially for subcutaneous use in this vulnerable patient population. [3]