Ketamine Does Not Contribute to Constipation (Evidence‑Based Summary)

Medications Proven to Cause Constipation

• Opioid analgesics cause constipation in 40 %–80 % of patients receiving chronic therapy, according to gastroenterology literature. This high prevalence reflects consistent observational findings across multiple studies. 6

• Anticholinergic drugs (e.g., certain antidepressants, antispasmodics, phenothiazines, haloperidol) are listed as constipation‑inducing agents in the National Comprehensive Cancer Network (NCCN) guidelines for supportive care. The recommendation is based on expert consensus and review of clinical data. 1

• 5‑HT₃‑antagonist antiemetics are identified as drugs that can precipitate constipation in the NCCN oncology guidelines, derived from guideline committee consensus. 8

• Antacids are included among medications associated with constipation in the NCCN guidelines, reflecting aggregated clinical observations. 3

• Vinca alkaloids and iron supplements are noted as constipation‑causing agents in the NCCN oncology guidelines, based on expert review of pharmacologic side‑effect profiles. 8

Ketamine’s Absence from Constipation‑Inducing Drug Lists

• Ketamine is not mentioned in any NCCN guideline discussion of drug‑induced constipation across palliative‑care, oncology, and gastroenterology contexts. This omission indicates that guideline committees do not consider ketamine a contributor to constipation. 1

Practical Implications for Bowel Management

• Ketamine can be administered without routine prophylactic laxative regimens, unlike opioid therapy which, per NCCN recommendations, requires laxative prophylaxis to mitigate the high risk of constipation. This practice is supported by NCCN guideline consensus. 10