Biosynthetic "human" insulin is now manufactured for widespread clinical use using genetic engineering techniques using recombinant DNA technology. More recently, researchers have succeeded in introducing the gene for human insulin into plants and in producing insulin in plants, specifically safflower. It is anticipated that this technique will reduce production costs.
Several of these are slightly modified versions of human insulin which, while having a clinical effect on blood glucose levels as though they were exact copies, have been designed to have somewhat different absorption or duration of action characteristics. They are usually referred to as 'insulin analogues'. For instance, the first available, insulin lispro, does not exhibit a delayed absorption effect found in 'regular' insulin, and begins to have effect in as little as 15 minutes. Another rapid acting analogue is NovoRapid with a similar profile. Both are rapidly absorbed due to a mutation in the sequence that prevents the insulin analogue in forming hexamers. In stead, the insulin molecule is a monomer which is more rapidly absorbed. Using it therefore does not require the pre-planning required for other insulins which begin to take effect much later (up to many hours) after administration. Another type is extended release insulin; the first of these was 'insulin glargine'. These have a steady effect for the entire time they are active, without the peak and drop of effect in other insulins; typically, they continue to have an insulin effect for an extended period from 18 to 24 hours. Similar another protracted insulin analogue 'Levemir' is based on a fatty acid acylation approach. A fatty acid (myristyric acid) is attached to this analogue which in turn associates the insulin molecule to the abundant serum albumin. This in turn extends the effect and in addition it reduces the risc of hypoglycemia. Both protracted analogues only need to be taken once-daily and is very much used in the type 2 diabetes market as the basal insulin. A mix combination of a rapid acting and a protracted insulin is also available for the patients making it more likely for the patient to achieve an insulin profile that mimics that of the body´s own insulin release.
Unlike many medicines, insulin currently cannot be taken orally. Like nearly all other proteins introduced into the gastrointestinal tract, it is reduced to fragments (even single amino acid components), whereupon all 'insulin activity' is lost. There has been some research into ways to protect insulin from the digestive tract, so that it can be administered orally or sublingually. While experimental, several companies now have various formulations in human clinical trials.
Insulin is usually taken as subcutaneous injections by single-use syringes with needles, an insulin pump, or by repeated-use insulin pens with needles.
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