Investigation Into the Viscosity of Commercial IG Preparations

All intravenous immunoglobulin (IVIG) products carry a boxed warning for the risks of renal dysfunction and thromboembolic events (TEEs). Patient-related thrombotic risk factors include hyperviscosity, a condition in which increased blood “thickness” heightens the risk of TEEs. Studies have shown that IVIG infusions increase plasma viscosity. To assess whether the viscosity of IVIG products themselves might be a parameter of interest in product selection, particularly for at-risk patients, we undertook an initial investigation into the viscosities of 5 commercially available 10% IGIV products. Experiments were performed using: ALYGLO (immune globulin intravenous, human-stwk 10% liquid), GC Biopharma; OCTAGAM10% (immune globulin intravenous [human] 10% liquid), Octapharma; GAMUNEX-C (immune globulin injection [human], 10% caprylate/chromatography purified), Grifols Therapeutics LLC; PRIVIGEN (immune globulin intravenous [human], 10% liquid), CSL Behring LLC; and GAMMAGARD LIQUID (immune globulin infusion [human] 10%), Takeda Pharmaceuticals. IgG content was determined using the Lunatic system (Unchained Labs, USA). Samples were diluted with deionized water as necessary to normalize concentrations for accurate viscosity comparison. Sample viscosities were determined using a Honeybun microvolume viscometer (Unchained Labs, USA) at 4, 10, 15, 20, 25, and 37°C. Results were reported in centipoise (cP), a unit of measurement for a fluid’s resistance to flow, with a higher cP indicative of greater viscosity. The results at 25°C were as follows: ALYGLO: 2.587 cP; OCTAGAM: 2.646 cP; GAMUNEX-C: 2.598 cP; PRIVIGEN: 2.598 cP; GAMMAPLEX: 2.598 cP. At 37°C, viscosities were further reduced, ranging from 2.263–2.309 cP across all products. For reference, the viscosity of human plasma at 25°C generally ranges from 1.5 to 1.72 cP. All products showed consistent, sequential decreases in viscosity as temperatures increased, with the lowest values observed at 37°C. These findings suggest that IVIG infusions administered at room temperature (25°C) may be a safety consideration for the prevention of TEEs and that viscosity decreases even further once products equilibrate toward body temperature. The consistency between the first and second analyses supports the robustness of these observations and warrants further investigation to identify potential differences in the viscosities of commercially available IVIG products, which may have implications for product selection in at-risk patients. Figure 1. Tabular data are included as downloadable supplement files.