Enteral feeding tubes may be helpful for nutrition support in patients that cannot eat but have a working gastrointestinal tract. Administering medication in these tubes is useful for patients that cannot take it another route, but issues can arise. This article discusses some factors that can affect medications given this route and ways to avoid common issues related to administration down a feeding tube.
The placement site of the tube can alter the medication efficacy. Most oral medications are absorbed in the small intestine. Some medications, for example antacids, sucralfate, and bismuth, act locally in the stomach and would provide minimal benefit if administered in a tube that bypasses the stomach. In addition, if medications that rely on extensive first-pass metabolism, such as opioids, beta-blockers, or tricyclic antidepressants, are administered in a tube that ends in the jejunum, they will have increased absorption and greater efficacy possibly leading to more adverse effects. First-pass metabolism is a result of the drug entering the liver after absorption in the gut resulting in much of the drug being metabolized before reaching the systemic circulation. This is taken into consideration when dosing this type of medication and if it is bypassed, by administering into the jejunum, it leads to a higher concentration of drug than intended
The tube size also plays an important part in deciding medication administration. Small bore tubes are more comfortable for the patient but are more likely to clog, especially with medication administration. Only liquid medications should be used in a Dobhoff tube to prevent clogging. Large bore tubes are less likely to clog, but it is important to know that if the tube is being used for suctioning, medications should not be given down that tube because they might be removed before absorption.
Medications should not be administered or mixed with tube feedings because they can interact and lead to negative effects. Phenytoin is the most well-known medication in this situation, decreasing blood levels of the drug up to 75% when administered with tube feeds. It is recommended to hold feedings 2 hours before and after each dose if possible. Warfarin efficacy is reduced when administered through a feeding tube and INR should be monitored more closely. Other medications can form precipitates with tube feedings, such as iron supplements and sucralfate. Liquid medications prepared as syrups can be acidic and denature proteins in the feeding, causing clumps and leading to clogs.
Liquid dosage forms are the preferred form for enteral administration of medications. Suspensions and elixirs are preferred over syrups because they are less likely to clog. Many liquid preparations contain large amounts of sorbitol which can cause GI upset or diarrhea. There are also liquid medications with high osmolality, above 1000 mOsm/kg, which will draw water into the GI tract and lead to cramping, diarrhea, or vomiting. A few examples of medications with high osmolality include acetaminophen elixir, cimetidine solution, metoclopramide hydrochloride syrup, and lithium citrate syrup.
Medications that should not be crushed include tablets that are controlled-release, enteric-coated, teratogenic, or irritants. Disrupting the controlled-release mechanism can cause toxic blood levels of the drug and enteric-coated drugs do not crush well and when mixed with water will bond together creating a clog. If the medication is teratogenic it should not be crushed for the safety of the staff. Capsules with microencapsulated pellets, such as Depakote Sprinkle and Effexor XR, can be opened and the pellets can be administered in large bore feeding tubes.
The tube should be flushed with a small amount of water both before and after medication administration. Flushing helps prevent clogs and interactions between different medications or tube feeds. Also, if medications are scheduled to be administered at the same time, they should not be given down the tube at the same time but rather administered separately while flushing the tube in between each medication. This is important because medications can precipitate or interact if given together increasing the risk of clogs or decreasing efficacy. Also, it is recommended to hold feeding for 30 minutes before and after the medication is administered if it requires administering on an empty stomach and the tube ends in the stomach. No holding is required if the tube ends in the intestine rather than the stomach.
If clogging does occur it is recommended to intervene as soon as possible by flushing with warm water. It is not recommended to try flushing with acidic liquids, such as soda or cranberry juice, because it has not shown to be more effective than water and might compound the issue by precipitating proteins from the feedings. Instead, an alkalized enzyme solution should be used. It is prepared by crushing one sodium bicarbonate 324mg tablet and one pancrelipase tablet mixed together with 5mL of water.
Overall, medication use in feeding tubes can be complicated with many different factors involved. Problems such as clogged feeding tubes and disruption of medication efficacy negatively affect both the patient and the staff. It is important to recognize why these problems can occur and to follow proper administration guidelines to prevent them in the future.
Submitted by: Alexander Fringes, PharmD Candidate 2016
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