GASTROMARK
Clinical safety rating: caution
Comprehensive clinical and safety monograph for GASTROMARK (GASTROMARK).
Gastromark (ferumoxsil) is an oral superparamagnetic contrast agent used in MRI. It contains iron oxide particles that create local magnetic field inhomogeneities, reducing T2* signal in the gastrointestinal tract, thereby improving visualization of abdominal organs by darkening the bowel lumen.
| Metabolism | Not metabolized; iron oxide particles are eliminated unchanged via feces. |
| Excretion | Renal: 23-31% as intact compound; fecal: 69-77% via biliary elimination; very little metabolism. |
| Half-life | Terminal elimination half-life: 3.1-3.5 hours; clinical context: supports rapid clearance from the body after imaging. |
| Protein binding | Negligible (<1%), primarily free drug in plasma. |
| Volume of Distribution | Vd: approximately 0.2 L/kg (16 L in 70 kg adult); restricted mainly to extracellular fluid. |
| Bioavailability | Oral: <1% due to poor absorption and extensive biliary excretion; designed to remain in GI tract for luminal contrast. |
| Onset of Action | Oral: 15-30 minutes for gastric lumen enhancement; rectal: 30-60 minutes for colon enhancement. |
| Duration of Action | Gastric enhancement: 20-60 minutes post oral dose; colonic enhancement: variable up to 2-4 hours post rectal administration; duration sufficient for imaging window. |
Orally, 30-60 mL of a 1% suspension (300-600 mg iron) diluted in water or juice, given 12-24 hours prior to MRI examination; may be repeated if necessary.
| Dosage form | SUSPENSION |
| Renal impairment | No dose adjustment required for any degree of renal impairment; safety in ESRD not established. |
| Liver impairment | No dose adjustment required for any Child-Pugh class; has not been studied in severe hepatic impairment. |
| Pediatric use | Not recommended for use in pediatric patients; safety and efficacy not established. |
| Geriatric use | No specific dose adjustment; use caution due to potential increased sensitivity and comorbid conditions. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for GASTROMARK (GASTROMARK).
| Breastfeeding | It is not known whether ferumoxsil is excreted in human milk. Because many drugs are excreted in human milk, caution should be exercised when Gastromark is administered to a nursing woman. M/P ratio not available. |
| Teratogenic Risk | Gastromark (ferumoxsil) is an oral magnetic resonance imaging contrast agent. No adequate and well-controlled studies in pregnant women. Animal reproduction studies have not been conducted. Risk cannot be ruled out; use only if clearly needed. FDA Pregnancy Category C. |
| Fetal Monitoring |
■ FDA Black Box Warning
None
| Serious Effects |
["Hypersensitivity to ferumoxsil or any component of the formulation","Known iron overload disorders (e.g., hemochromatosis, hemosiderosis)"]
| Precautions | ["Hypersensitivity reactions including anaphylaxis","Iron overload in patients with hemochromatosis or iron accumulation disorders","Interference with iron absorption if taken with food","Use with caution in patients with known allergies to iron or dextran"] |
| Food/Dietary | Take after a light meal (low-fat, non-gassy foods) to reduce side effects and improve distension. Avoid heavy, fatty, or high-fiber meals before the exam as they may delay gastric emptying and affect image quality. Do not take with antacids or iron supplements as they may interfere with contrast efficacy. |
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| No specific monitoring required beyond standard clinical observation for adverse reactions. Monitor for hypersensitivity reactions. Fetal monitoring not indicated as the agent is not absorbed systemically and acts locally in the gastrointestinal tract. |
| Fertility Effects | No studies on fertility effects have been conducted. Based on mechanism (non-absorbed oral contrast), significant effects on fertility are unlikely. |
| Clinical Pearls | GASTROMARK (ferumoxsil) is an oral contrast agent for MRI. It contains superparamagnetic iron oxide particles that shorten T2* relaxation, causing signal loss in the bowel. Administer after a light meal to delay gastric emptying. Patients with iron overload disorders should use cautiously. Image acquisition should start 30-45 minutes post-ingestion for optimal small bowel distension. Do not use in patients with known hypersensitivity to iron products. |
| Patient Advice | Take GASTROMARK exactly as prescribed, usually after a light meal. · Drink the entire bottle; notify your doctor if you cannot finish it. · You may experience mild gastrointestinal discomfort, nausea, or diarrhea. · Inform your doctor if you have a history of iron overload or hypersensitivity. · This medication is for oral use only; do not inject or mix with other drinks. · Tell your doctor if you are pregnant, breastfeeding, or have kidney problems. |