Dhiren Patel, PharmD, and Serge Jabbour, MD, give an overview of the basal and prandial properties of U-500 insulin therapy and discuss patient selection criteria.
Dhiren Patel, PharmD: The patients who would be appropriate for U-500 insulin or concentrated insulin would be any patients who are approaching or are right around 200 units of total daily insulin. You would add up all of their basal insulin requirements, as well as their bolus insulin requirements. If you’re seeing that they’re averaging above 200 units, those patients would be ideal candidates to initiate U-500 because of the basal/bolus properties that it provides. Twice-a-day dosing would cover those patients for 24 hours with 2 injections. And it minimizes the injection burden. If they’re getting 200 units a day, they’re probably doing multiple injections, basal/bolus, and some injections may require multiple injections for any given specific time point. And so, this allows minimizing the injection burden and converting them over to just 2 injections. The volume that’s being injected is much less.
Looking at the properties of U-500, there’s basal and bolus properties. By that I mean the U-500 is Humulin R, which is a regular insulin, so you would expect it to behave like a regular short-acting insulin. But the kinetics of it are very different, and it behaves more like an NPH (isophane insulin) in terms of its duration.
So, typically, when I’m converting patients over from a typical basal/bolus regimen, I’ll start a patient on twice a day. There’s a twice-a-day algorithm; there’s a 3-times-a-day algorithm. Clinically, most of my patients will get started on a twice a day, which could be a 50/50 split or a 60/40 split. Then, they get to about 300 units of total daily insulin, when I get back to a 3-times-a-day regimen, where you could do a 40/30/30 split. That’s based off of both the protocols that exist, as well as the algorithms, but also from clinical practice.
The reason I bring that point up is to highlight that unique feature where, when a patient is injecting it twice a day, it’s behaving more like a basal insulin. When the patient shifts to it 3 times a day, it’s now behaving more closely to a bolus insulin, because they’re injecting it with each meal. Again, I think that is a very unique property. I think that for pharmacists, it’s really important, because in some situations, that might mean discontinuing prior insulin therapy. But in a certain scenario, if a patient’s using it 3 times a day, they might have a background of other insulin. It’s indicated only for monotherapy, but we know in practice that’s very different. And so, I think that’s an area where pharmacists can play a huge role: making sure if the prior insulin therapy should be discontinued or continued and, if so, making sure that a dose conversion happened correctly.
Serge Jabbour, MD: When I switch patients from U-100 to U-500 insulin, education is absolutely important. I do most of it myself in the office, where I choose the dose of U-500. I explain to patients that it’s a different insulin that combines basal and prandial properties at the same time. I show them the pen. I show them how to use it, but not everyone may do this. That’s why we might depend on pharmacists to do some teaching of these patients going to fill their insulin. So, I think it’s very important from the pharmacist’s standpoint to understand the U-500, how it works, and to make sure to counsel patients on the importance of that insulin. It combines, as I said before, those basal and prandial properties, which is really unique to it.