Drug Discov Ther. 2021;15(5):241-247. (DOI: 10.5582/ddt.2021.01083)

Physicochemical properties of brand and generic infusion fluid preparations (Part 3): Investigation of type 1 hypotonic infusion fluids

Takei S, Katsuyama S, Hori Y

In Japan, the increasing use of generic drugs has led to a reduction in drug prices, which affect the steady supply of drugs. A "basic drug" system was introduced to rescue these drugs by eliminating gaps in drug prices among preparations with the same constituents. "Type 1" hypotonic infusion fluids, which are potassium-free and commonly used to treat dehydration, meet the definition of a "basic drug" in Japan, and there are no drug price gaps. However, there is a lack of information on the physicochemical properties of "type 1" hypotonic infusion fluids, making it difficult to identify differences among them. Extracellular fluid-replacement solutions and "type 3" hypotonic infusion fluids have different pH and titratable acidity. Here, we measured the pH, titratable acidity, and osmolality of six different "type 1" hypotonic infusion fluids and compared the results with respect to risk avoidance considering metabolic acidosis, changes upon mixing, and vascular pain. There was a significant difference, or trend toward significance, in titratable acidity, which is a risk factor for metabolic acidosis in patients with impaired renal function, and pH, which is a risk factor for change upon mixing, among all combinations except one of the infusion fluids. Thus, the selection of "type 1" hypotonic infusion fluids for children with immature renal function, elderly patients with impaired renal function, and patients with unknown pathophysiology, considering titratable acidity and pH, is an effective strategy for risk avoidance.

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