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Calculating Concentrated Insulins

Sep 06, 2016


ecently, representatives from Eli Lilly came to the school of pharmacy to educate faculty and fourth-year professional students on concentrated insulin, such as Humalog (insulin lispro U-200) and Humulin R (insulin regular U-500). While I was listening to the speaker talk about the devices, I reflected on how much diabetes has changed over the years.

When I was in pharmacy school studying diabetes in the fall of 2004, the faculty member taught us about metformin, sulfonylureas, acarbose, rosiglitazone, and pioglitazone. She also mentioned insulins that were available such as NPH, regular insulin and others. At this time, I never had to calculate a U-500 dose. As a faculty member for the past 10 years, I would speak to fourth-year professional students on my ambulatory care learning experience about concentrated insulins in order to make them aware about the potential opportunity of dispensing and/or counseling on these medications when they become an independent pharmacist. With the new concentrated insulin pens, it is essential to educate students about these options because as it may be that the use of concentrated insulin increases over the next couple of years. It is important to remember that there are other concentrated insulins on the market, such as Toujeo (insulin glargine U-300) and Tresiba (insulin degludec U-200).

Keep in mind that everyone may have different approaches depending on the experience and comfort level with U-500 insulin.

After the discussion on these two specific products, the students wanted to review how to calculate Humulin R U-500 from U-100 insulin, but they also specifically wanted clarification on the dose from a vial or the pre-filled pen. Here is an example of the calculation that I reviewed with the students, but keep in mind that everyone may have different approaches depending on the experience and comfort level with U-500 insulin:

  • Patient is injecting 200 units per day of a U-100 basal insulin and 50 units per day of U-100 bolus insulin.
  • Add 200 and 50 for total daily dose of insulin (250 units), as U-500 insulin has basal and bolus properties in terms of pharmacokinetics.
  • Split the total daily dose into two daily injections (breakfast – 60% of the total daily dose and dinner – 40% of the total daily dose).
    • Breakfast: 250 x 0.60 = 150 units of U-500
    • Dinner: 250 x 0.40 = 100 units of U-500
  • If the pre-filled pen is used, then the patient can dial to 150 or 100 units and inject at the appropriate time.
  • If a U-100 syringe were used, then 150 units divided by 5 (same with 100 units) would give you the dose – 30 units and 20 units, respectively.
  • If a tuberculin syringe is used, then 150 units divided by 5 (same with 100 units) would give you the dose, but it would need to be changed to a volume – 0.3 mL and 0.2 mL, respectively.

There are several review articles and small studies evaluating the use of concentrated U-500 insulin. I think we will see the use of concentrated insulin increase in order to decrease the volume that a patient may inject, especially when doses of U-100 insulin are over 80 or 90 units per day. The concentrated insulins are available in pre-filled, disposable pens to prevent medication errors when drawing from a vial; however, the Humulin R U-500 via will remain available for prescribing.

What will be interesting is more evidence to add to the pool for concentrated insulin, such as this insulin used in a pump. But what is the evidence for U-500 with a GLP-1 receptor agonist? Would the patient require less insulin? I would assume, but how much of a change? Would the patient lose weight? Again, I would predict, but how much weight loss? I expect more evidence at regional, state, national, and international diabetes conferences that can be added to the pool of current literature from other conferences and journals.

So, what are your thoughts about concentrated insulin? Are you using them in practice? If so, what types of patients have been switched to these insulins? Were any of the patients insulin-naïve? Share your thoughts with the group and through social media, so we can learn from each other.

Jennifer ClementsAbout the Author

Jennifer Clements received her Doctorate of Pharmacy from Campbell University in 2006 and completed a primary care residency at a Veterans Affairs Medical Center in 2007. She is also a certified diabetes educator and board certified in pharmacotherapy. Currently, she is the Interim Chair and Associate Professor in the Department of Pharmacy Practice at Presbyterian College School of Pharmacy.

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  1. Sep 25, 2016

    I believe the dosing on U-500 pens was to make it easier for pharmacists to comprehend.  My patients on U-500 using vial and syringes or pumps had no problem understanding that the insulin was concentrated and therefore the "units"they were taking had been carefully calculated to provide the dosing they needed.

    Enter the U-500 pen, with unit per unit dosing and the confusion it caused to patients (BUT, not to pharmacists).  I worked with one patient to change from vial to pen.  When he was given the total units he needed as 200 before breakfast and supper, vs 40 before those meals, he panicked and stated he would not take that much because it did not sound same.

    Taking a page from Lilly's U-200 Humalog, why did they not go this route, where the patient dialed up their normal dose, previously calculated from U-500 into U-100 equivalents.  Big Mistake!  Patient's have been used to one method, but it has been changed for the comfort of pharmacists!

    Bonnie Stone, RD CDE

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