Evaluating the Safety and Efficacy of Different Routes of Neostigmine Administration for Acute Colonic Pseudo Obstruction: a Prospective Randomized Trial

Acute colonic pseudo-obstruction (ACPO) is a severe form of colonic ileus seen in patients hospitalized with a variety of medical and surgical conditions. The most serious complication is spontaneous colonic perforation, which occurs in 3% of cases with a mortality rate of up to 50%. The risk of perforation is greater in those patients with a cecal diameter >12 cm, although the duration of dilation might be more important than the cecal diameter. A significant number of patients will respond to the conservative measures enumerated in the abstract.

Endoscopic decompression of the dilated colon is undertaken commonly to prevent spontaneous perforation. However, it is performed under suboptimal conditions (unprepared and distended colon) increasing the risk of complications with a morbidity rate of 3% and a mortality rate of 1%. Furthermore, although effective initially in 69% of cases, 40% of them will have at least one recurrence. To decrease this recurrence rate, endoscopic placement of a drainage tube is now advocated. Patients who fail to respond to conservative therapy and colonoscopic decompression will require surgery, which has a mortality rate of up to 26%.

In an effort to find a more effective, noninvasive therapy, Ponec et al., introduced and highlighted the effect of IV neostigmine (2 mg over 3-5 min). Neostigmine was significantly more effective than placebo in rapidly decreasing colonic dilation in the majority of patients with ACPO. Although it has a short half-life, a single IV dose of 2 mg of neostigmine was sufficient in most cases to restore colonic motility.

It is important to be aware of contraindications to using parasympathetic agents, including bradyarrhythmia and history of bronchospasm. Patients need to be monitored while neostigmine is infused, and atropine should be available in the event of complications. Patients with renal insufficiency might be at higher risk of complications as a significant quantity of the drug is excreted in urine.

In light of these contraindications, administration by the subcutaneous (SQ) route has been utilized intermittently for ACPO. Data for use of SQ administration of neostigmine in adult patients are limited to one multi-institutional observational study, one case series, and two case reports in acute medical and palliative care patients. Although these case reports describe a range of dosing, the SQ route of administration appears to be attractive alternative to IV administration for this indication, with a time to effect of 8 to 10 hours.