The other day I saw a patient with type 1 diabetes who had switched from a multiple injection regimen using glargine (Lantus brand) and lispro (Humalog brand) to one with regular (R) and NPH (N) insulins. She did this because of the high costs for the glargine and lispro insulins (over $100/bottle); the R and N insulins were about $20 a bottle. She asked me if I thought that was ok and what could she could do to decrease the frequency of hypoglycemia with the “new” insulin regimen; she was having hypoglycemia most afternoons and at 1-2 am.
A History Lesson
I told the patient that the R and N regimen (R before meals and N at bedtime) was what we used routinely for multiple injection insulin regimens, or “MDI” regimens before the new fancy (and expensive) insulins became available in the late 1990s, that N and R still work well, but that the time course of action of those insulins is quite different than the newer insulins. So, we had a little review of insulin pharmacokinetics. I explained that the newer short-acting insulins, such as lispro and aspart have rapid onset of action and are mostly gone 2 hours after the injection (or bolus, in patients using insulin pumps). Regular insulin has a much slower onset of action (30 minutes or longer) and the effects on blood glucose last much longer- up to 8-10 hours or or even longer. That is why, for most patients taking R insulin before meals, mid-morning, mid-afternoon, and mid-evening snacks are necessary to avoid hypoglycemia (with smaller main meals). Thus, for this patient, the afternoon and 1-2 am episodes of hypoglycemia were likely the result of a bit too much R insulin before lunch and supper. She could solve the problem by cutting back a bit on the R insulin doses or better yet, by having small snacks mid-afternoon and mid-evening or at bedtime. If she took the snack route, she would need to cut down a bit on calories at lunch and supper, if she didn’t want to gain weight. I told her the most important thing was to prevent the hypoglycemia and that she could “have her cake and eat it too,” that is, save money and have well-controlled diabetes, if she just made a few adjustments to her treatment plan.
What About R insulin In Pumps?
Most younger docs do not remember that before we had the newer short-acting insulins, R insulin was used in insulin pumps (we’ve been using insulin pumps since the late 1970s). It worked well as long as one understood the insulin pharmacokinetics. I think the biggest difference between using R and either lispro or aspart insulin in pumps is that with R the basal rate during the day is generally lower than overnight, and just the opposite with the newer insulins. Of course, this is expected since the day-time boluses with R “drag out” longer and contribute significantly to the basal insulin effects during the day.
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