What does the speed of insulin absorption after a subcutaneous injection depend on

After the injection, a reservoir of insulin is created at the point of infusion, which is then progressively absorbed from the capillaries of the region and enters the circulation. The speed of absorption of the subcutaneous reservoir depends on a number of factors:

• The insulin compound. Every type of insulin has a different profile of absorption. The rapid acting soluble insulin (reguar insulin) is injected subcutaneously in the form of insulin hexamers. These are diffused in the subcutaneous tissue and are split progressively into smaller complexes (trimers ! dimers ! monomers) which are more easily absorbed by the capillaries. Isophane insulin (NPH) contains protamine in stoicheiometric proportion with insulin (i.e., it contains the same amount of protamine as insulin), which renders the formed hexamers more stable in the subcutaneous tissue, so that their absorption is delayed. The insulins that contain zinc are absorbed more slowly, because of higher stability of the hexamers, caused by the presence of zinc. In very rapid acting insulin analogues, the change that has occurred in the insulin molecule renders the hexamers unstable, resulting in an accelerated absorption of insulin. In the slow acting Glargine analogue, however, the change of the molecule, and also the addition of zinc, renders the hexamers more stable in the subcutaneous tissue, with as a consequence its slower and constant absorption. The slow action of the insulin analogue Detemir is achieved partly via binding of its molecule with albumin, from which it is progressively released, achieving the characteristic action profile of this particular insulin.

• Concentration and dose of insulin. The concentration of insulin is identical in all the available products: 100 units (IU)/ml. The insulin dose definitely influences the speed of absorption with higher doses leading to its extension.

• Site of injection. The density of the capillary network is higher in the abdominal wall in comparison to the arm or the thigh. Consequently, the speed of absorption is, for the vast majority of insulin products, higher in the abdomen than other sites.

• Local blood flow. The factors that influence blood flow in the region of injection also influence the speed of insulin absorption. Thus, heat (sunbathing, a hot bath), muscular exercise and massage increase the speed of absorption whereas the cold decreases it.

• Technique of injection. The speed of insulin absorption is markedly influenced if, by mistake, the injection is performed intramuscularly or intradermally. The speed of absorption after an intramuscular injection is considerably accelerated. The possibility of error is more likely in lean individuals, especially if longer needles (> 10 mm) are used, or if an erroneous technique is performed (no folding of skin).

Certain insulins (those found in a suspension form that are 'turbid', for example, isophane insulin and the mixtures that containing it) should be shaked before the injection. If shaking is omitted or if it is performed wrongly, the concentration of insulin in the subcutaneous tissue can be very different from what is desirable.

Diabetes 2

Diabetes 2

Diabetes is a disease that affects the way your body uses food. Normally, your body converts sugars, starches and other foods into a form of sugar called glucose. Your body uses glucose for fuel. The cells receive the glucose through the bloodstream. They then use insulin a hormone made by the pancreas to absorb the glucose, convert it into energy, and either use it or store it for later use. Learn more...

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