Last month, Clinic Chat featured rapid- and short-acting insulins. This month, let’s talk about intermediate- and long-acting insulins, which are designed to counteract the glucose the liver releases into the blood around-the-clock – and in some cases, to also cover food. Read on for more on these insulins and their applications.
Intermediate-acting Insulin - Protaphane and Humulin NPH Intermediate-acting insulin starts working after 1-2 hours, peaks between 4 and 6 hours and lasts up to 12 hours. If given in the morning intermediate-acting insulin may act as both background insulin to cover glucose released by the liver, and as meal-time insulin, as lunch generally coincides with the time the insulin peaks. Pros Intermediate-acting insulins are sometimes the first insulins that are prescribed to people who have been newly diagnosed because there is no requirement for an extra injection at lunchtime, which may be difficult – for example in a school setting. Cons Some people experience low blood glucose levels around mid-morning as their insulin starts to build towards its peak. Accurately dosing intermediate-acting insulin to perfectly marry up with lunchtime carbs can be challenging, and can result in variable blood glucose during the afternoon. Long-acting insulins – Lantus, Levemir and Tujeo There are three long-acting insulin options available on Australia’s Pharmaceutical Benefits Scheme (PBS), each with slightly different profiles. Lantus and Levemir are available to people of all ages, and Tujeo can be used by people aged 18 and older. Lantus When injected, Lantus forms a depot under the skin, from which small amounts of the insulin are continuously released into the bloodstream. Lantus should be taken at a similar time each day and is generally taken at night. Pros Lantus doesn’t have a peak and lasts up to 24 hours. Cons Some people report that physical activity impacts the action of their Lantus dose. When blood flow past the insulin depot increases, such as during exercise, the rate at which the insulin molecules are released into the bloodstream goes up. More insulin being released may increase hypo risk during exercise. Levemir When injected, Levemir molecules bind to small proteins called albumin which carry it around the bloodstream. The insulin breaks free from albumin at a consistent rate over 16-20 hours. Pros Blood flow does not impact the rate at which Levemir molecules are released, making it a good option for active people. It can be dosed once or twice daily, so the user can dose morning and night according to their level of activity. It can also be useful for people who experience a dramatic dawn phenomenon (early morning blood glucose rise) as they can take a larger dose at night to help mitigate the rise, without impacting how much insulin they have onboard during the day too much. Cons Some people find Levemir causes painful injection site reactions. Tujeo Tujeo is essentially triple-strength Lantus. It offers a stable, consistent action profile for up to 36 hours. Even though Tujeo is 3x more concentrated than Lantus, the conversion is actually 1:1, because the volume of 1 unit of Tujeo is one-third of the volume of 1 unit of Lantus. Pros As Tujeo has no peak and a very stable action profile, it can be a good insulin for people having issues with overnight hypoglycaemia. Cons Similarly to Lantus, once you’ve injected a dose of Tujeo you’re committed to it for the next 24+ hours. Some people find this inflexibility challenging – for example if you’re planning on being extra active the following day, reducing your bedtime dose of insulin may cause you to run high overnight, while taking a normal dose may mean you run low during activity the next day. Next month, we’ll look at newer insulins from Novo Nordisk, ultra-long-acting Tresiba and mixed insulin Ryzodeg – don’t miss December’s Clinic Chat!
Time-Action Profiles of Longer Acting Insulins