How enteral feeding tubes affect medicines

Vincent Cassidy, Medicines Information Scientist, RDTCPublished Last updated See all updates

A knowledge of the different types of enteral feeding tube is important when recommending options for medicines administration

Enteral feeding recommendations

Healthcare professionals should consider enteral tube feeding in people who are malnourished or at risk of malnutrition as defined in National Institute for Health and Clinical Excellence NICE Guidance Nutrition support for adults (CG32), and have:

  • inadequate or unsafe oral intake, and
  • a functional, accessible gastrointestinal (GI) tract

This article provides some information on the factors for consideration and their possible affect on medicines being administered via enteral feeding tubes.

Factors affecting medicines administration

Enteral feeding tubes may be broadly classified by their entry sites and where the tube terminates in the GI tract.

You should consider the following factors before giving a medicine via an enteral feeding tube:

  • Tube size
  • Tube material
  • Site of tube (and associated site of medicine absorption)
  • Tube Function
  • Feed timing – feeds may interact with medicines to reduce bioavailability.
  • Administration Route – other administration routes to consider include intravenous, transdermal, buccal, etc.
  • The critical nature of the medicine, e.g. antiepileptics, etc.
  • Formulation – modified release tablets should not be given via a feeding tube. More viscous liquids e.g. syrups may clog tubes, as may larger medicine particles.

What injections can be given orally or via enteral feeding tubes?‘ provides a list of injections which may be given enterally.

Tube Size

Tube diameters are expressed using the ‘French’ unit. This measurement refers to the external diameter of the tube. One French unit represents 0.33mm.

Small bore tubes may be between 5-12 French.

Large bore tubes are those which measure more than 14 French.

Administration issues

Smaller bore tubes are more comfortable for the patient but may present clogging problems for enteral feed solution or medicines.

For medicine administration, a tube with a diameter of at least 8Fr should be suitable.

Narrow and long tubes are likely to become blocked by larger drug particles or viscous solutions.

Tube material

Tubes may be made out of silicone, latex, polyvinylchloride (PVC), or polyurethane (PUR).

Administration issues

Adsorption

As with intravenous giving sets, medicines may adsorb onto the tube material itself, reducing bioavailability of the medicine.

Smaller lumen

The material which a tube is made out of can also affect the size of the lumen.

Softer materials such as silicone and latex will require more material. Thus, the lumen size of tubes made of these materials will be smaller than those made of PVC or PUR, even if the French size (diameter) is the same.

Site of Tubes

The implications of a medicine’s absorption site should be considered for all patients receiving medicines via feeding tubes.

Recommendations

Nasal feeding tubes are generally used for short term enteral feeding as they require less maintenance and are less invasive compared to percutaneous tubes..

NICE guidance on Nutrition Support for Adults (CG32) recommends that gastrostomy feeding should be considered in people likely to need long-term (4 weeks or more) enteral tube feeding. It also states that feeding tubes which terminate in the stomach are preferred unless the patient has upper gastrointestinal dysfunction.

Patients with severe gastro-intestinal reflux disease, pancreatitis or gastroparesis are more likely to have tubes which end in the small bowel (e.g. duodenum, jejunum or ileum).

Administration issues

Care should be taken to check that the tube does not bypass the site of medicine absorption.

Some medicines cannot be administered through tubes to sites below the stomach because gastric acid is needed for their absorption or the absorption is altered at the intestinal site.

Gastric acid

Medicines that require an acidic environment to be absorbed optimally, may have a reduced bioavailability e.g. ketoconazole.

First-pass metabolism

Conversely, reduced first pass first pass metabolism may result in increased bioavailability of some medicines such as opioid analgesics, beta-blockers, and tricyclic antidepressants.

Drug absorption

Tubes which terminate in the jejunum cause a particular concern for medicine administration as the tube may bypass the site of absorption and the medicine will be in the GI tract for a reduced amount of time.

Medicines such as antacids, sucralfate, and bismuth are unlikely to work as they have a local effect in the stomach.

Tube Function

Tubes which are being used for aspiration or drainage should not be used for the purpose of administering medicines.

This is particularly important for multi-lumen tubes as care must be taken to ensure medicines are administered into the correct lumen.

Types of Tubes

There are a variety of enteral feeding tubes available.

Nasogastric (NGT)

NGT enters through the nose and exits in the stomach can have a range of sizes of 6-12 Fr for feeding and 12–16Fr for aspiration.

Nasoduodenal (NDT)

NDT enters through the nose and exits in the duodenum this is classed as a small bore tube

Nasojejunul (NJT)

NJT enters through the nose and exits in the jejnum this is a fine bore tube

Percutaneous Gastrostomy (PEG)

PEG tube enters the abdomen and exits in the stomach this can be a fine or a large bore tube

Percutaneous jejunostomy (PEJ)

PEJ tube enters the abdomen and exits in the jejunum this is a small bore tube

Percutaneous Gastrojejunostomy (PEGJ)

PEGJ tube enters the abdomen and exits in the jejunum via the stomach this is a small bore tube

Orogastric (OG)

OG tube enters the mouth and exits in the stomach This can be either a small or a large bore tube.

Types of Feed

It is common for patients with enteral feeding tubes to be on enteral tube feeds and these can be given in a variety of regimens.

Continual

Continual feeding will require interruptions for drug delivery but is the preferred method for jejunal tubes.

Cyclic

Cyclic administration involves continuous feeding for a particular period.

If administration is overnight, this may help to reduce the problems associated with medicine-nutrient interactions.

Bolus

Bolus feedings, which most closely resemble normal feeding patterns, are used for gastric administration of feeds and can allow medicine administration to be spaced between feedings.

Intermittent

Intermittent feeding involves longer periods of medicines administration than bolus so medicines can be carefully planned around feedings.

Formulation

The British Association for Parenteral and Enteral Nutrition (BAPEN) provide information on the advantages and disadvantages associated with particular medicines formulations.

In general the preferred formulations are liquid solutions and soluble tablets.

Crushing tablets

Crushing tablets and opening capsules should only be considered as a last resort, because of potential dosing inaccuracies, occupational exposure and increased dose preparation time.

Medicines that should not be crushed include:

  • Modified/extended release tablets
  • Enteric coated tablets
  • Cytotoxics
  • Hormones

Change history

  1. Added Formulation section with link to BAPEN information
  1. Published