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|Newsletter: Tips from the Plumber's Helper: Liquid Medications|
Tips from the Plumber’s Helper: Liquid Medications
Mark Klang, MS, RPh, BCNSP, PhD
A common question with tube feeding is, “What formulation should we use for drug administration through a feeding tube?” The most common reply is, “Use the liquid formulation.” However, just because it’s in a liquid form doesn’t mean it is ideal for a feeding tube.
The liquid formulations of most medications are thick, sweet, and have low drug concentration. This is because most drugs taste bad, and the formulation was likely developed for kids. Syrups and suspensions have thickeners to help those with swallowing difficulties; sweeteners to mask the taste of bitter medications; and cellulose to maintain a uniform suspension. Most of the suspending agents are acidic to help make the weak base drugs being delivered dissolve more easily. These thickeners, sweeteners, and suspending agents are called “excipients.” For the feeding-tube patient, none of these excipients are needed, and in some cases they contribute to adverse effects.
Osmolarity is the amount of stuff in a liquid. The more small molecules (“stuff”), like sugars and alcohols, in a liquid, the higher the osmolarity. Most manufactured and pharmacy-compounded liquid formulations have very high osmolarity. The osmolarity of most liquid medications is much greater than 1000 mOsm/liter, for example, whereas the osmolarity of stomach fluids is about 280 mOsm/liter.
The presence of high osmolar liquid in the GI tract will cause a shift of fluid from surrounding tissues. The greater the difference in osmolarity, the higher the shift of fluid. This shift will feel like cramping, and the resulting extra fluids in the GI tract will contribute to diarrhea formation. This issue is so common, it is surprising how few compounders and manufacturers are aware of the consequences from the formulations they provide.
Crushing Solid Medications
The next time a drug is available in both a solid and liquid formulation, ask if the solid medication can be crushed, rather than being put into a liquid form. In most cases, solid dosages can be made into suspensions with tablets mixed in water; these have small shifts in osmolarity, so there is less cramping and/or diarrhea.
For capsules of non-hazardous nature, open the back of the syringe and open the capsule; dump capsule contents into the syringe; close the syringe; and add water to the syringe. Allow a slurry to form and then administer. For hazardous medication, like chemotherapy, add the tablet/capsule intact into the back of the syringe, close the syringe, and add water. Most drugs form a slurry within twenty minutes. These methods do not work well for time-release or sublingual medications.
Rinse the feeding tube with about 5–10 mL water, administer the drug slurry, and follow with 5–10 mL plain water.
Check with your pharmacist on guides for which drugs can be administered by simple crushing and mixing with water. (The Institute for Safe Medicine Practices offers a list called “Oral Dosage Forms That Should Not Be Crushed,” online at www.ismp.org/tools/donotcrush.pdf.) ¶
General recommendations on medication administration through a feeding tube can be found on the Oley website, www.oley.org (see “Tube Feeding Troubleshooting Guide” and “Drug Administration through a Feeding Tube,” by J. Boullata, PharmD, RPh, BCNSP, LifelineLetter, Sept/Oct 2011).
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