A percutaneous endoscopic gastrostomy (PEG) tube is a feeding device inserted through the abdominal wall directly into the stomach, primarily to deliver nutrition and fluids when a patient cannot safely swallow. Administering medication through a PEG tube is complex and differs significantly from taking a pill by mouth. The tube’s narrow diameter makes it highly susceptible to clogging, which interrupts feeding and drug delivery. Improperly administered medications can also lose their therapeutic effect or become toxic, requiring a careful understanding of which formulations must be avoided.
Mechanisms of Medication Incompatibility with PEG Tubes
The primary reasons certain medications cannot be administered through a PEG tube relate to physical characteristics, altered drug absorption, and destruction of specialized drug release profiles. The tube’s narrow internal diameter presents a significant physical barrier. Highly viscous liquids, thick syrups, or inadequately crushed tablets create a slurry that adheres to the tube wall and causes a blockage. Mixing multiple medications simultaneously can also trigger chemical reactions, such as crystallization or precipitation, forming clumps that obstruct the tube lumen.
A second major incompatibility involves disrupting the drug’s intended absorption and metabolic pathway. Many drugs are formulated to dissolve in the stomach’s acidic environment or require specific enzymes in the upper small intestine for proper absorption. If a medication is delivered to a different location, or if its chemical structure is altered by crushing, it may not dissolve correctly. Bypassing the upper gastrointestinal tract, where medications like iron supplements and warfarin are absorbed, can significantly reduce their efficacy.
The third mechanism concerns the integrity of the medication’s dosage form, specifically the coatings and matrices that control drug release over time. Crushing a tablet destroys these complex delivery systems. Immediate release of the entire dose is known as “dose dumping,” causing a sudden surge in drug concentration and increasing the risk of toxicity. Conversely, manipulation may cause the drug to be poorly absorbed, resulting in sub-therapeutic levels and treatment failure.
Medication Formulations to Never Administer Via PEG Tube
Several specific types of medication formulations are strictly prohibited due to the risks of tube blockage, toxicity, or treatment failure.
Time-Release Medications
Any medication labeled as sustained-release (SR), extended-release (ER), controlled-release (CR), or delayed-release must not be crushed or opened. These formulations use specialized coatings to release the drug slowly over many hours. Crushing them destroys the time-release mechanism, leading to the rapid and uncontrolled release of the entire dose, which is a significant safety hazard.
Enteric-Coated Formulations
Enteric-coated (EC) tablets are prohibited because their coating prevents dissolution in the acidic stomach, ensuring release only in the small intestine. Crushing an EC tablet exposes the drug to stomach acid, potentially inactivating it. Furthermore, the crushed particles are often sticky and clump together, causing tube obstruction. Capsules containing enteric-coated microgranules or beads should also be avoided, as these small particles can clump and block the device.
Oral Mucosa Absorbers
Formulations designed for absorption through the oral mucosa must be administered as intended and never pushed through a PEG tube. This includes sublingual and buccal tablets, which are formulated for rapid absorption directly into the bloodstream, bypassing the digestive system. If crushed or dissolved, the drug is sent to the stomach where it may be rapidly inactivated or poorly absorbed, rendering the medication ineffective.
Effervescent Tablets
Effervescent tablets, which bubble when dissolved, should not be administered via the tube. This poses a risk of gas buildup, which can cause patient discomfort or potentially rupture the tube.
Essential Steps for Safe Administration and Preparation
Safe medication administration through a PEG tube requires meticulous preparation and adherence to a strict protocol.
Consultation and Authorization
Before modifying any solid oral medication, a pharmacist or prescribing physician must be consulted. This confirms that an alternative, compatible formulation, such as a liquid or a tablet that can be safely crushed, is not available. Crushing a tablet or opening a capsule without professional authorization is considered an unlicensed use of the drug and shifts liability to the administrator.
Preparation Technique
If crushing is deemed safe, the tablet must be pulverized into the finest possible powder using a dedicated crusher. The powder is then dissolved completely in a small volume of purified or sterile water. Tap water is discouraged because its chemical contaminants can interact with the drug. Administer each medication separately, one at a time, to prevent unwanted chemical interactions and physical precipitation.
Flushing Protocol
The PEG tube must be flushed with water before, between, and immediately after the administration of each medication dose to ensure tube patency and complete drug delivery. For adults, a flush volume of at least 15 milliliters of water is recommended before the first medication and after the final medication. A 15-milliliter flush is also required between each individual dose. This ensures no medication residue is left inside the tube to interact with the next drug or the enteral feeding formula.