Osmolality, pH, and Compatibility of Selected Oral Liquid Medications With an Enteral Nutrition Product

When selecting medication for feeding tube administration, the liquid formulation is selected, so as to avoid obstructions that may occur from incompletely crushing a solid dosage form. Liquid medications can present issues of intolerance and compatibility when administered via a feeding tube. A predictor of intolerance is the liquid's osmolarity, and a predicator of compatibility is the liquid's pH value. This study examines 62 liquid formulations for their osmolality, pH, and physical compatibility with enteral nutrition (EN) formulas. These medications were selected as being the most commonly dispensed liquid medications from our outpatient pharmacy department. This study measures osmolality using freezing point depression. Depending on the dose, the osmotic load of a liquid medication may cause cramping and diarrhea. The pH value is predictive of potential interactions with the EN formula. Many drugs are weak bases and require acidic vehicles for optimal stability. The acidic liquids are especially reactive with enteral formulas that contain intact proteins. The result of this interaction can result in an occlusion of the feeding tube as the proteins form a gel-like clog. This study combined the liquid medication directly with the EN formula to determine the potential for feeding tube occlusion. Some drugs formed a solid mass in the test tube immediately, whereas others only presented granules, which may later contribute to obstructing the feeding tube. The prescriber should be aware of the potential impact of their choice in formulation, both in terms of the gastrointestinal tolerance and potential for interaction with coadministered nutrition.