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

Medication Administration Considerations With EN

If the medications are needed and alternative routes of drug delivery are not options, then the medications may be given through enteral feeding tubes. Several factors should be considered before administering medications concomitantly with EN. As discussed previously, feeding tube size and placement site should be considered. Gastric access is generally preferred over jejunal administration because gastric tubes are larger and less prone to clogging and because the stomach may be more tolerant of hypertonic medications.[6,10] Gastric feedings may be administered by bolus or intermittent methods; EN and medications may thus be given at separate times.

Liquid Preparations

Selecting the most appropriate dosage form is also something to consider. Liquid preparations are the preferred formulations when possible because they are readily absorbed and are less likely to cause tube occlusions. Elixirs or suspensions are generally favored over syrups since syrups are more likely to cause clumping when exposed to EN.[10,13,16] An important safety measure to take when administering liquid medications through enteral feeding tubes is to make sure that the drugs are drawn up and dispensed only in oral syringes (not syringes intended to give parenteral injections) in order to avoid the accidental parenteral administration of an oral formulation.[10,13]

Adjustments in the medication dosage or frequency may be necessary when changing formulations. This is particularly important when switching from an extended-release product to a liquid preparation, which is usually immediate release and requires more frequent dosing. Another concern when administering liquid preparations to adults is that many are designed for use in children; therefore, large volumes of the drug must be given in order to achieve an adult dosage, and this could cause intolerability.[5,10,16]

Although oral liquid medications are preferred for enteral administration, they may potentially cause adverse effects. Many liquid preparations are extremely hyperosmolar or contain large amounts of sorbitol, increasing the risk of GI intolerance. This is particularly troublesome when a large volume of drug is dispensed per dose.[14,16] Hypertonic medications may not be well tolerated when delivered into the small intestine. The stomach, though, is able to dilute hyperosmolar substances with gastric juices before transferring the contents into the duodenum. However, if the hypertonic medications are administered too rapidly into the stomach, they may be "dumped" into the small bowel, resulting in osmotic diarrhea.[17,18] If possible, hypertonic medications, especially when undiluted, should not be administered directly into the small intestine, such as with a jejunostomy tube. This may cause bloating, nausea, cramping, and diarrhea.[18,19] Diluting the hyperosmolar liquid medication with 10–30 mL of sterile water before delivery through the feeding tube may help prevent these intestinal intolerances from occurring. More water may be needed when diluting medications that are either extremely hypertonic or being delivered directly into the small intestine.[5,19] Unfortunately, osmolality data for some medications are not usually readily available, and the manufacturer or package insert must be consulted.[19] Some liquid medications with a high osmolality are listed in Appendix A. The average osmolality values of other liquid preparations have been published elsewhere.[17]

The sorbitol component of the medication itself can also cause GI distress with liquid preparations. Sorbitol is an inactive ingredient used as a sweetening agent to improve medication taste as well as stability, but large amounts (i.e., ≥ 20 g per day) may cause an osmotic laxative effect, resulting in cramping and diarrhea. Even doses as low as 10 g per day may lead to bloating and flatulence.[19,20] Although most liquid medications only contain a small amount of sorbitol, patients may be taking multiple products that contain this ingredient, thus increasing the cumulative effects.[5] Unfortunately, since sorbitol is considered an inert substance, manufacturers may not always list it on the product label. Even when inactive ingredients are included on the label or in the package insert, the exact amount of sorbitol in the liquid preparation is generally not listed. Sorbitol content may also differ among manufacturers of a particular product. The best way to determine the sorbitol content of a liquid medication is to contact the drug manufacturer.[19,20,21] Appendix B lists some medications that contain sorbitol, although the amount may vary by manufacturer. The sorbitol content of various oral liquids has been published elsewhere.[20,21]

Suspensions, which are often used for antibiotics, may be a more desirable type of liquid formulation. They generally contain less sorbitol than other liquid products, and most reconstituted antibiotic preparations have no sorbitol. Although suspensions may have a high osmolality, diluting with water will help decrease the tonicity.[19,20,21]

When patients experience adverse GI effects, oftentimes the enteral tube feeding is blamed, but the hyperosmolality and sorbitol content of the liquid medication may be the causes. Several commonly used medications, such as acetaminophen liquid, have a high osmolality and contain sorbitol. Pharmacists can play a key role in identifying the potential medication culprits and evaluating the osmotic load and sorbitol amount. It may be necessary to change the medication to a therapeutically equivalent agent that does not contain sorbitol or an agent that has a lower osmolality. Switching the administrative route may also be helpful. Changing the medication formulation (e.g., from a liquid to a crushed tablet or opened capsule) may be another option.[18,19] Generally, injectable formulations are not administered into the GI tract because these dosage forms are not apt to survive in gastric acidity, which can result in reduced drug absorption.[14] The osmolality of parenteral drugs may be higher, potentially causing osmotic diarrhea, and the cost may be much greater.[9] Although liquid medications are more convenient to administer via a feeding tube, it may not be the best option if GI distress occurs.

Some liquid formulations are not appropriate for administration via the enteral tube. These include lansoprazole oral suspension granules and mineral oil, which are too viscous and may occlude the tube. Sucralfate suspension is also not suitable because it may cause an insoluble mass or bezoar formation.[10,13,16,22]

Syrups should also be avoided, particularly when mixed with enteral formulas. Syrups with an acidic pH (≤4) are the most problematic because of their physical incompatibility with EN formulations, which can result in clumping or thickening and may cause the feeding tube to become clogged. Similar problems with tube occlusions may occur with ferrous sulfate elixir, which is not a syrup but is also very acidic. Some liquid preparations that are not compatible with enteral tube feedings and cause clumping or precipitation are listed in Appendix C. Further diluting the syrup with water cannot prevent the physical incompatibilities between EN and syrups. An alternative liquid preparation is preferable. If this is not possible, the enteral feeding should be interrupted and the tube flushed with at least 30 mL of water before and after administering the incompatible syrup in order to separate the medication from the EN; the tube feeding may then resume.[19,23] Not all syrups are considered physically incompatible with enteral products. Syrups are generally less preferable to other liquid formulations because many syrups have pH values of <4 and cause compatibility problems.[23]

Solid Dosage Forms

When a liquid preparation is inappropriate or unavailable, certain solid dosage forms may be used for administration into feeding tubes. Most simple, compressed tablets, including those that are sugar- or film-coated, are immediate-release products and may be crushed. Crushing the tablet results in minimal pharmacokinetic changes to the drug and is similar to swallowing it whole. Crushing some preparations could cause a bitter taste if taken orally, but this is not an issue for administration via a feeding tube. Tablets should be crushed to a fine powder using a mortar and pestle and then mixed with 15–30 mL of water before delivery through the tube. Similarly, hard gelatin capsules that contain a powdered drug may be opened and the contents diluted in 10–15 mL of water to form a slurry before administration.[12,13,19,24]

Administration of liquid-filled soft gelatin capsules is more challenging. One end of the capsule may be pierced with a needle, and its liquid contents can be squeezed out and mixed with water. A concern with this method is that all of the contents may not be removed from the capsule, which can result in underdosing. Alternatively, the entire soft gelatin capsule may be dissolved in a container of warm water and all of the contents given. Care should be taken not to administer the undissolved gelatin portion into the tube because this may cause occlusion.[9,12,19]

Special care should be taken with some extended-release capsules that contain beads or pellets and certain capsules filled with enteric-coated granules. These capsules may be opened and emptied into the feeding tube, but their contents should not be crushed. Examples of medications that may be administered this way include diltiazem (Tiazac, Biovail Pharmaceuticals, Morrisville, NC) and verapamil (Verelan, UCB Pharma, Smyrna, GA).[5,12,25] Ferrone et al.[26] described how delayed-release pancreatic enzyme capsules that contain enteric-coated microspheres (Pancrecarb MS-4, Digestive Care, Inc., Bethlehem, PA) may be opened and the contents mixed with applesauce or apple juice before administration through the feeding tube. A potential complication with pouring capsule contents through any enteral access device is that tube occlusions may occur, so large-bore feeding tubes (≥14 French) are preferred.

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