Fast insulin and slow insulin
Since it began to be used in therapy in the 1920s, insulin has gradually transformed diabetes from a deadly disease into a manageable condition with increasing ease. Initially, bovine and porcine forms were used, with important risks of sensitization and allergic reactions, but starting from the 1980s a very pure insulin identical to human insulin began to spread. This protein substance is produced by genetically modified bacterial strains to give it the ability to synthesize human insulin. Thanks to the further refinement of pharmaceutical techniques, today the diabetic has various types of insulins available: ultra-rapid analogues (insulin lispro and aspart), rapid (or normal), semi-slow, NpH, slow, ultra-thin and various premixed combinations of the previous ones. all thanks to the "simple" modification of some parts of the protein structure of human insulin produced by bacteria. The distinctive characters of the various types of insulin are essentially three:
- latency time (interval between administration and onset of the hypoglycemic therapeutic effect);
- peak time (interval between administration and maximum hypoglycemic effect);
- duration of action (interval between administration and disappearance of the hypoglycemic effect).
To learn more: Complete list of articles on the site dedicated to insulin-based drugs
The ultra-rapid analogues (insulin lispro and aspart) go into action 10-15 minutes after injection, peak in 30-60 minutes and last for about four hours. These characteristics make them ideal for concomitant intake with meals and allow the diabetic to face sudden and unexpected changes in his usual lifestyle.
Rapid (or normal) insulin has a half-hour latency, peaks in two to four hours, and subsides after four to eight hours. It is used before meals to control hyperglycemia that follows food intake and to quickly lower the blood sugar level when it gets too high.
Semi-slow insulin goes into action after one to two hours, peaks in action within two to five hours, and is inactive in eight to twelve hours. Similarly to the previous one, it is used to control postprandial hyperglycemia and is often associated with slow insulin.
Insulin NpH (Neutral protamine Hagedorn) contains a substance (protamine) which slows down its action; in this way the latency reaches two to four hours, the peak occurs six to eight hours after the injection and the overall duration reaches 12-15 hours. Usually two injections a day allow sufficient glycemic control.
The slow insulin, which contains zinc, has characteristics quite similar to Nph: latency of one to two hours, peak of 6-12 hours and duration of 18-24 hours. Like the previous one, theoretically it allows satisfactory glycemic control. with just two injections a day.
The ultra-slow insulin contains a greater quantity of zinc, which further delays its action. Thus, the latency rises to four to six hours and the peak to eight to fifteen hours, while the disappearance of the effect occurs after 18-24 hours. For this reason, only one injection per day is enough, associating it with small doses of rapid insulin (eg before meals).
There is also an analogue of ultra-slow human insulin, called insulin glargine, which has a latency of four to six hours, lasts more than 24 hours and is characterized by the absence of the peak (in other words, its activity remains constant for duration of action). In some patients, a single injection of this product per day achieves good glycemic control.
Pre-made insulin blends
The preconstituted mixtures (the most common are NpH: normal in the ratio of 70:30 or 50:50) have an average latency of half an hour, a peak time that varies according to the formulation and a duration of action up to 18-24. hours. Their use allows you to customize insulin therapy as much as possible.
Which and how much insulin to use?
For a diabetic person, the therapeutic amount of insulin depends on various factors such as age, weight, movement, residual functional activity of pancreatic B cells and the amount of food absorbed during the day.
There is no standard one-size-fits-all insulin therapy. In fact, each person has different clinical characteristics, habits, rhythms and lifestyles. The diabetologist, in close collaboration with the patient, defines the "insulin scheme", that is to say a daily "schedule" in which to enter the times of administration, the quantity and type of insulin (or insulins) most suitable.
Purely as an indication, as many units of insulin per day as the weight of the individual should be used; this parameter, as well as the combination of the different insulin preparations, depends on the therapeutic choice recommended by the doctor. physiological trend of insulin in a healthy person (click on the image to enlarge) characterized by a "basal" level (which has the function of regulating the production of glucose by the liver) and by peaks during meals. This trend is roughly reproduced by combining fast-acting insulin (to manage increased mealtime blood sugar levels, with injection just before each meal) with slow-acting insulin (to manage glucose production under fasting conditions). the scheme undertaken is fundamental the collaboration of the patient, who will have to learn how to inject insulin (also the way in which the injection is performed is important for good glycemic control), cope with emergencies, respect the scheme, monitor several times a day blood glucose and note the changes, reporting to the doctor any symptoms of hypoglycemia / hyperglycemia or changes in behavioral habits.
The insulin pumps
Disposable syringes and preloaded pens (with which it is possible to perform more injections by replacing only the needle) are now supported by the so-called insulin pumps. These devices allow subcutaneous infusion of the drug 24 hours a day, through a catheter connected to a controlled insulin reservoir. from a computer (for basal secretion) and from the patient himself for the "bolus infusion" (higher amounts of insulin at meals rich in carbohydrates or episodes of unexpected hyperglycemia).