Common anti-nausea drug triggers intestinal swelling: Case report
Promethazine linked to 69-year-old woman’s angioedema
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A medication commonly used to treat nausea after surgery and allergic reactions triggered angioedema of the intestine (intestinal angioedema) in a woman recovering from stomach cancer surgery, according to a case report.
The woman’s angioedema symptoms and imaging findings resembled those of potentially life-threatening gastrointestinal complications that may require emergency surgery. However, after doctors identified the anti-nausea medication promethazine (sold under the brand name Phenergan, among others) as the likely cause, her symptoms resolved with supportive treatment and no need for surgery.
“The present case is, to our knowledge, the first report of promethazine-induced intestinal angioedema,” the researchers wrote. They said the case “underscores the importance of recognizing drug-induced [causes] to prevent unnecessary surgery and enable conservative management.”
The study, “Intestinal Angioedema Induced by Promethazine in a Postoperative Patient With Gastric Cancer: A Case Report,” was published in Clinical Case Reports.
Angioedema occurs when fluid leaks into deeper layers of the skin or mucous membranes, causing swelling attacks that can affect different parts of the body. When the intestine is involved, fluid accumulates beneath its inner lining, causing abdominal pain, nausea, vomiting, and, in some cases, gastrointestinal bleeding.
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Intestinal angioedema has been reported in people taking ACE inhibitors, a class of medications commonly used to treat high blood pressure. Intestinal angioedema associated with ACE inhibitors is a form of drug-induced nonallergic angioedema, which typically arises when certain medications lead to higher-than-normal levels of bradykinin, a signaling molecule that promotes swelling.
The researchers believe intestinal angioedema associated with promethazine is more likely a form of acute allergic angioedema, which is triggered by histamine, an inflammatory signaling molecule released by immune cells during allergic reactions.
Despite their different mechanisms, both types can result in symptoms and imaging findings that closely resemble other gastrointestinal conditions requiring emergency surgery. Recognizing the condition early is important because stopping the offending medication and providing supportive care usually allows patients to recover without surgery.
The pair of researchers in China described what they said was the first reported case of promethazine-induced intestinal angioedema.
The 69-year-old woman in the report had undergone surgery for stomach cancer six months earlier and had since completed four rounds of chemotherapy. After being hospitalized for rectal bleeding and abdominal pain, she was discharged but returned to the hospital less than 24 hours later with recurrent bleeding and abdominal pain.
A CT scan showed widespread swelling of the colon wall, fluid in the pelvis, and inflammatory changes in the surrounding fatty tissue. Given her recent cancer surgery and chemotherapy, doctors initially considered several serious complications, including reduced blood flow to the intestine, bowel perforation, or a severe infection of the colon.
A physical examination showed that the woman was stable. Her abdomen was soft and not swollen, she had no signs of irritation of the lining of the abdomen, her bowel sounds were normal, and she continued to pass stool. Together, these findings reduced the likelihood of bowel perforation and advanced intestinal ischemia (severe damage caused by a lack of blood flow to the intestine).
Doctors reviewed her medications and saw that her symptoms developed soon after she received promethazine to treat nausea and vomiting. The timing, together with the CT findings and blood findings, led them to diagnose the woman with promethazine-associated intestinal angioedema.
The doctors opted for conservative treatment rather than surgery, temporarily stopping food by mouth and providing nutrition through a vein to allow the woman’s bowel to recover. Five days later, her abdominal pain and bleeding had resolved, and a follow-up CT scan showed that the swelling and fluid had disappeared. She was able to resume eating and was discharged from the hospital without her symptoms returning.
The researchers noted that although promethazine “is widely prescribed for allergic disorders,” it can rarely trigger acute allergic reactions and intestinal angioedema. They said doctors should “consider this adverse reaction” in people who develop rectal bleeding and abdominal pain after receiving the medication, while also ruling out more serious conditions such as reduced blood flow to the intestine, bowel perforation, or colon cancer.
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