By Leslie Vaughn, RPh
In our last blog, we reviewed the basics of immune globulin (IG) indications and listed the items that may be considered during brand selection. This blog delves deeper into the key considerations when selecting a brand based on patient specific factors.
Most of the IG products on the market today are available as a ready-to-use liquid formulation in either a 5%, 10% or 20% solution (the 20% solution is for subcutaneous use only). For individuals who need to limit the amount of fluid they receive, the 10% solutions for intravenous administration may be the best choice.
All of the IG products on the market contain varying amounts of IgA (one of the four antibodies found in blood). For most people, receiving some IgA isn’t problematic. It is of concern, however, when someone is known to have antibodies against IgA, or to have reacted to IgA in the past.
Most of the early generation IG products were stabilized with a sugar such as sucrose or maltose. Today, the majority of products on the market are no longer stabilized with a sugar, but a few still are. One adverse reaction to a sugar, which is rare but has been reported with IG administration, is kidney failure. The cause of kidney failure is not completely known, but there is a strong association with sucrose-containing products, rapid rates of infusion and diabetes. Another issue noted with products stabilized with maltose is a possible interaction with strips that test for glucose in the blood. The maltose may cause an erroneous reading indicating glucose is high when it really isn’t. Most of the test strips have modified formulations to prevent these erroneous readings when maltose is present.
Osmolality is the solute concentration contained in the IG solution. A higher osmolality means there is a higher concentration of the IG solution. Our blood has an osmolality of about 285 to 295. Most of the current IG products have an osmolality fairly close to that of our blood. Higher osmolality solutions, also known as hyperosmolar, may be associated with an increased risk of a person developing a blood clot after the infusion. Dehydration can also cause our blood to become hyperosmolar, which is one of the reasons people receiving IG therapy are encouraged to drink a lot of water before, during and after the infusion.
Routes of Administration
IG can be administered intravenously through a vein (IVIG), or subcutaneously under the skin (SCIG). For people receiving large doses of IG for autoimmune disorders, the SCIG route of administration may not be possible due to the large volume of solution needed for a dose. For someone receiving a smaller dose, it is possible to receive the dose in four weekly SCIG increments rather than one larger IVIG dose per month. Things to consider when deciding between the SC and IV route are the total volume of drug needed to make up the dose, the condition of the person’s skin (those with very thin skin don’t do as well as those who have thicker or normal skin) and the person’s body style (very thin people may not have enough fatty tissue in the space between the skin and the muscle to tolerate the infusion). Conversely, a person with very small veins or who has difficult getting an IV started may be a great candidate for the SC route of administration. Last, some of the side effects experienced with IV infusions may be significantly decreased when switched to SC. So, for those who have difficulty tolerating IV, SC may be a good option.
Many manufacturers, distributors and specialty pharmacies have an IG comparison chart that shows the difference between brands. Let us know if you would like one!