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PFAT5 and the Evolution of Lipid Admixture Stability
1Memorial Sloan Kettering Cancer Center, New York, New York klangm@mskcc.org.
Abstract:
PFAT5 is defined by United States Pharmacopeia Chapter 729 as follows: the "percentage of fat residing in globules larger than 5 µm (PFAT5) for a given lipid injectable emulsion [is] not to exceed 0.05%." The unstable aggregates are trapped in lungs, liver, and the reticuloendothelial system. Large particles will accumulate in pulmonary capillaries, which are between 4 and 9 µm in diameter. Over the years, there has been an evolution of methods to characterize and define intravenous fat emulsion (IVFE) stability when combined as a total nutrient admixture (TNA). Many studies have claimed IVFE stability measuring mean particle size, zeta potential, and visual checks. Interestingly, none of the studies that claimed the TNA as stable identified an unstable one through testing. This report reviews those parameters and shows they were not a valid measure of lipid stability. The PFAT5 parameter has emerged as the only validated measure of lipid stability. There are clinical consequences of using lipids that exceed the PFAT5 limit. This parameter is applicable to both manufactured and compounded lipid preparations. The clinician should be aware of the limitations of much of the literature concerning the lipid stability assessment. More stability studies are needed using PFAT5 to identify the actual limits of TNA compounding.
Insights
The percentage of fat larger than 5 µm (PFAT5) is the only validated measure for lipid injectable emulsion stability. Previous methods like particle size are unreliable, and exceeding the PFAT5 limit has clinical consequences.
Area of Science:
- Parenteral nutrition
- Lipid emulsion stability
- Pharmacopeial standards
Background:
- Intravenous fat emulsions (IVFEs) are crucial in total nutrient admixtures (TNAs).
- Assessing IVFE stability in TNAs is critical for patient safety.
- Traditional methods for assessing lipid stability lack validation.
Purpose of the Study:
- To review traditional methods for assessing IVFE stability in TNAs.
- To highlight the limitations of current stability assessment parameters.
- To establish the percentage of fat larger than 5 µm (PFAT5) as the validated measure of lipid stability.
Main Methods:
- Review of existing literature on IVFE stability assessment.
- Analysis of traditional parameters: mean particle size, zeta potential, and visual checks.
- Emphasis on the United States Pharmacopeia Chapter 729 definition of PFAT5.
Main Results:
- Traditional methods (particle size, zeta potential, visual checks) are not valid measures of lipid stability.
- The PFAT5 parameter is the only validated method for assessing lipid stability.
- Exceeding the PFAT5 limit (0.05%) can lead to accumulation of unstable aggregates in organs.
Conclusions:
- Clinicians must be aware of the limitations in current literature regarding lipid stability assessment.
- PFAT5 is applicable to both manufactured and compounded lipid preparations.
- Further research using PFAT5 is needed to define the actual limits of TNA compounding.
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