Medication Administration Through Enteral Feeding Tubes

Nancy Toedter Williams, Pharm.D., BCPS, BCNSP

Disclosures

Am J Health Syst Pharm. 2008;65(24):2347-2357. 

In This Article

Feeding Tube Size and Placement Site

Two important things to consider when administering medications through a feeding tube include the tube size and placement site. The outer lumen tube diameters are typically measured in French units (1 French unit = 0.33 mm) and are often designated as small-bore (e.g., 5–12 French) or large-bore (e.g., ≥ 14 French) tubes.[6,7,12] Small-bore tubes are placed into the stomach (e.g., NG, gastrostomy) or small bowel (e.g., ND, NJ, jejunostomy, percutaneous endoscopic jejunostomy, needle-catheter jejunostomy) and are used for feeding or administering medication.[5] Small-bore tubes are more comfortable but have a greater likelihood of becoming clogged by medications or thick EN formulations. NG tubes are also available in a larger diameter (e.g., Salem sumps). Large-bore NG tubes can be used for feeding or administering medication, but their primary functions are gastric suctioning and decompression. Another function of large-bore NG tubes is the measurement of gastric pH or residual volumes. These large-bore tubes are stiffer and cause greater patient discomfort, but they are less prone to clogging than smaller diameter tubes. When NG tubes are used for gastric suctioning, medications should not be administered via this route because they can also be removed with frequent suctioning. However, if drug delivery through the NG tube is necessary and the GI tract is working, then clamping the NG tube, if the patient can tolerate it, for at least 30 minutes after giving a medication may improve absorption before reattaching the suction. Other large-bore tubes include OG, gastrostomy, and PEG tubes; these are also less likely to occlude.[5,6,7,10,12]

The feeding tube placement site also affects drug absorption. Most oral medications are absorbed in the small intestine, but for some the stomach is the target for drug action and absorption. Therefore, if the feeding tube is placed in the small bowel, certain medications may have minimal benefit because the stomach is bypassed. These medications include antacids, which neutralize stomach acid, as well as sucralfate and bismuth, which both form a protective barrier in the stomach. Additionally, when certain medications that are characterized by extensive first-pass hepatic metabolism (e.g., opioids, tricyclic antidepressants, β-blockers, nitrates) are administered into the jejunum, increased absorption and greater systemic effects may occur.[5,10,12,13] The antifungals ketoconazole and itraconazole may also have decreased bioavailability when administered via intestinal feeding tubes. These medications require gastric acidity for optimal absorption, and the environment is less acidic as the feeding tube tip moves further down the GI tract.[10,13,14] By bypassing the stomach, intrajejunal administration may also result in incomplete drug absorption because the stomach aids in medication disintegration and dissolution.[15]

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