Does Omnipaque (iohexol) have an osmotic effect in the management of small bowel obstruction?

From the Guidelines

Omnipaque does have an osmotic effect that can be beneficial in treating small bowel obstruction, as evidenced by its hyperosmolar properties which help draw water into the bowel lumen and soften impacted fecal material 1. When considering the use of Omnipaque for small bowel obstruction, it is essential to weigh the potential benefits against the risks. The osmotic effect of Omnipaque can help resolve partial small bowel obstructions by promoting movement of intestinal contents past the point of obstruction.

• The administration of water-soluble contrast agents, such as Omnipaque, has been shown to be safe in terms of morbidity and mortality, but adverse effects have been reported, including aspiration pneumonia, pulmonary edema, and dehydration 1.
• To minimize the risk of complications, the contrast medium should be administered when the stomach has been adequately decompressed through a nasogastric tube, and patients should be monitored for potential adverse effects, including nausea, vomiting, diarrhea, and rarely, allergic reactions.
• The dosage of Omnipaque can range from 50-150 ml, either orally or via nasogastric tube, depending on the clinical situation, and the concentration can be adjusted to 25-50% by diluting with water 1.
• It is crucial to note that the use of Omnipaque should be avoided in cases of complete obstruction, suspected perforation, or when surgery is immediately indicated, as it may worsen the condition or delay necessary surgical intervention.
• The most recent and highest quality study on this topic, published in 2021, highlights the importance of water-soluble contrast agents in the management of small bowel obstruction, including their prognostic and potential therapeutic value 1.

From the FDA Drug Label

The recommended dose of OMNIPAQUE 350 at a concentration of 350 mg Iodine/mL for adult oral pass-thru examination of the gastrointestinal tract is 50 mL to 100 mL. In a Phase I study, 150 mL of OMNIPAQUE 350 was administered orally to 11 healthy male subjects. The incidence of diarrhea was 91% (10 of 11) and abdominal cramping was 27% (3 of 11). Despite all of these events being mild and transient the occurrences were more than double that seen at the recommended doses. It is apparent from this finding that larger volumes of hypertonic contrast media, like OMNIPAQUE, increase the osmotic load in the bowel which may result in greater fluid shifts.

• Osmotic effect: Yes, OMNIPAQUE has an osmotic effect, as larger volumes of the hypertonic contrast media increase the osmotic load in the bowel, resulting in greater fluid shifts.
• Relevance to small bowel obstruction: The osmotic effect of OMNIPAQUE may be relevant in the context of small bowel obstruction, as it can cause fluid shifts and potentially exacerbate the condition. 2

From the Research

Omnipaque and Small Bowel Obstruction

• Omnipaque is a low-osmolar contrast medium that has been compared to the hyperosmolar contrast medium Gastrografin in the radiography of small bowel obstruction 3.
• A study found that Omnipaque retained its radiographic density in the small bowel better than Gastrografin, making it a better alternative for follow-through examinations of intestinal obstruction 3.
• However, the study also found that there was no significant difference between Omnipaque and Gastrografin in terms of spontaneous relief of symptoms in patients with small bowel obstruction due to peritoneal adhesions 3.

Osmotic Effect of Omnipaque

• The osmotic effect of Omnipaque on small bowel obstruction is not explicitly stated in the provided studies.
• However, a study on Gastrografin, a hyperosmolar contrast agent, found that it had a therapeutic effect in adhesive, partial small-bowel obstruction, prompting the resolution of obstructive episodes and shortening hospital stay 4.
• Another study found that Gastrografin had a therapeutic role in assigning patients to a non-operative course in adhesive small bowel obstruction, resulting in a decreased hospital stay 5.
• It is unclear if Omnipaque has a similar osmotic effect, but its low-osmolar properties may suggest a different mechanism of action compared to Gastrografin.

Clinical Use of Omnipaque

• Omnipaque has been used in the diagnosis and management of small bowel obstruction, particularly in identifying patients who may be treated non-operatively 3.
• However, the provided studies do not specifically address the use of Omnipaque in the treatment of small bowel obstruction, and its efficacy and safety in this context are not well established 6, 7.