With health care being delivered in the most cost-effective manner possible, many patients are discharged to home with an enteral feeding tube. Surgeons will insert more than a quarter million temporary or permanent feeding tubes in the United States in 2006.¹ Many patients themselves, long-term care staff members, and visiting nurses will rely on pharmacists' advice to keep these patients adherent and ambulatory.^2,3

Feeding tubes provide nutrition and hydration when patients cannot swallow or should not eat. Unlike parenteral nutrition, enteral feeding stimulates mesenteric blood flow and gastrointestinal secretions and may improve immune defense.^4,5 Of the enteral tubes, percutaneous endoscopic gastrostomy (PEG) tubes are preferred. They are more comfortable than nasogastric (NG) tubes, because they are located in the abdomen about the belt line, and they lower the likelihood of aspiration.^6,7

Regardless, enteral tubes invite controversy. Median survival among patients who have permanent feeding tubes is about 7 months, and mortality at 3 years approaches 80%.⁸ When patients or their families are ill-equipped to handle formula- related diarrhea, constipation, or clogged tubes, nutritional status will not improve.^9,10 Patients with cognitive impairment often pull tubes out, complicating home care.^8,11

The Mechanics

In enteral tube terminology, the initials describe where the tube's terminal tips lie. Thus, an NG tube begins at the nose and ends in the gastric area, an NJ tube goes from the nose to the jejunum, and a PEG tube is inserted through the skin into the gastric lumen.¹² Bolsters anchor the tubes internally and externally, but the tubes can move.

Most tubes are now polyurethane or silicone, because polyvinyl chloride (PVC) tubing must usually be replaced frequently. PVC also may react with some drugs or leach into the acidic gastric environment. Similarly, latex tubes are more fragile and can cause an allergic reaction. PVC and latex tubes are more likely to occlude than polyurethane tubes.¹²

Blockage is a constant concern with feeding tubes, and clog prevention is the best approach. Intermittent feeding with liberal flushing tends to cause fewer blockages than continuous feeding. Patients or caretakers must always flush tubes frequently with 3 to 6 oz of water and put only substances of minimal viscosity into the tube. Allowing formula bags to empty in place, using long tubing lengths or small diameters, and administering medications improperly also promote clogging.^13,14

If possible, obstruction should be disrupted with the tube in place; otherwise, the patient will need a new tube. Various experts have developed obstruction-removal procedures and devices, but they disagree about the best practice. Solutions of pancreatic enzymes, very dilute dishwashing liquid, cola, or meat tenderizer have been employed, as have cytology brushes and corkscrew-type devices.^15,16

Medication Via a Tube

The enteral tube also is often a medication conduit. Most tubes will have a main infusion port for formula delivery. Smaller side ports deliver fluid and medication, and a "balloon port" inflates the internal anchor. Patients must not use the balloon port for nourishment or medication, but giving medication via the formula port is not usually a problem.¹ Large 12-to 30-Fr gastric tubes generally are preferred over 8-Fr jejunal tubes for drug administration because the stomach tolerates hypertonic medications better than the bowel, and some drugs require gastric exposure.¹⁷

Pharmacists should ensure that patients and caregivers know wound-deterioration signs and symptoms (redness, weeping) and contact the primary care provider if necessary. If the tube's terminal tip moves, aspiration and progressive complications are possible. Before discharge, hospital staff members will show patients or caregivers how to check tube placement with respect to the pyloris before administering formula or medication.¹⁸ Hospital staff members will observe aspirate appearance or pH, or listen with a stethoscope while insufflating the tube with air. They might also measure the length of the tube that extends from the body, and compare it with its insertion length.^14,18

When medication is delivered via an enteral feeding tube, bioavailability, compatibility, complications, and interactions— particularly potential drug-nutrient interactions—must be considered. When medication and formula mix, physical precipitation (curdling) or viscosity change (thickening or separation) can occur. Carbamazepine, digoxin, and phenytoin may interact with formula, causing unpredictable blood levels. Antacids may bind to formula and cause occlusions; they should be given into the stomach, not the jejunum. A formula's vitamin K content may antagonize warfarin, necessitating monitoring.

Patients should discuss dosage forms with the pharmacist when presenting prescriptions. Altering some dosage forms could decrease or increase efficacy, potency, or tolerance. The Table lists specific concerns.

Physiologic incompatibilities ensue when high-osmolality liquid medications or high-sorbitol content irritates the gut. Calculating osmolality (the number and size of molecular and ionic particles per kilogram of solution) is difficult. Introducing high-osmolality solution to the gut and especially the jejunum can cause diarrhea, constipation, bloating or gas. Similar problems can follow the use of sorbitol-containing solutions. A change in the patient's gut motility will change clinical response to medication.

Administering Medications

Patients will need to have all equipment ready before starting. Caregivers or patients will check the tube position and close the enteral feeding line before giving medications. A hiatus—30 minutes before and 2 hours after the dose—is needed for drugs that require an empty stomach.¹⁷ For medication administered with food, the medication and formula should be given in sequence, not together. Drugs never should be added to the formula.¹⁸

Although most references recommend that medications be given individually, most clinicians allow patients to commingle vitamins. Caregivers or patients should flush the tubing with 30 mL of tap or boiled-then-cooled water. If the patient is fluid-restricted, the physician may reduce the amount of fluid used. If the tube length is longer or shorter than usual, more or less fluid may be needed.¹² Patients also should have a medication diary on which they record the doses given and flushing amounts.

Although liquid medication formulations have obvious advantages, they can be costly. Viscous or sugary proprietary liquids and large volumes should be diluted with 30 to 90 mL of water to lower their viscosity/osmolality. Patients or caregivers should macerate tablets or capsule contents in 15 to 60 mL of water using a mortar and pestle, or by placing the drug between 2 nestled medicine cups and crushing it with a heavy object. They can puncture liquid gel capsules and express their content or submerse and dissolve them. Injectable dosage forms sometimes can be used, again in an oral syringe, but generally these are more costly than oral forms, and their enteral absorption is unpredictable.

Go Easy Now!

Once the medication is ready, caregivers or patients should draw medication slurries one at a time into a large (>30-mL) oral syringe and inject the slurry slowly into the tube. To prevent error, regular parenteral syringes never should be used. Large syringes create less pressure and are less likely to rupture the tubing.¹⁶ After each dose, a 15-to 30-mL water (and only water) flush will keep the tubing patent. After the last medication is given, the patient or caregiver will either restart the feeding tube or use some type of reminder system to ensure that it will be restarted at the appropriate time.^2,16-18

Final Thought

Feeding and medicating via a feeding tube are a challenge for many patients. When the pharmacist is involved with other health care professionals and helps identify appropriate dosage forms and administration routes, the process and outcomes are significantly better.^19,20

Ms. Wick is a senior clinical research pharmacist at the National Cancer Institute, National Institutes of Health, Bethesda, Md. The views expressed are those of the author and not those of any government agency.

For a list of references, send a stamped, self-addressed envelope to: References Department, Attn. A. Rybovic, Pharmacy Times, Ascend Media Healthcare, 103 College Road East, Princeton, NJ 08540; or send an e-mail request to: arybovic@ascendmedia.com