Monday, September 10, 2007

The Basics of Insulin

Types of Insulin

Rapid-acting insulin, such as insulin lispro (Eli Lilly), insulin aspart (Novo Nordisk), or insulin glulisine (sanofi-aventis), begin to work about 5 minutes after injection, peak in about 1 hour, and continue to work for 2 to 4 hours.

Regular or Short-acting insulin (human) usually reaches the bloodstream within 30 minutes after injection, peaks anywhere from 2 to 3 hours after injection, and is effective for approximately 3 to 6 hours.

Intermediate-acting insulin (human) generally reaches the bloodstream about 2 to 4 hours after injection, peaks 4 to 12 hours later and is effective for about 12 to 18 hours.

Long-acting insulin (ultralente) reaches the bloodstream 6 to 10 hours after injection and is usually effective for 20 to 24 hours. There are also two long-acting insulin analogues, glargine and detemir. They both tend to lower glucose levels fairly evenly over a 24-hour period with less of a peak of action than ultralente.

Premixed insulin can be helpful for people who have trouble drawing up insulin out of two bottles and reading the correct directions and dosages. It is also useful for those who have poor eyesight or dexterity and is a convenience for people whose diabetes has been stabilized on this combination.

Characteristics of Insulin

The three characteristics of the four types of insulin are onset, peaktime, and duration.

Onset is the length of time before insulin reaches the bloodstream and begins lowering blood glucose.
Peaktime is the time during which insulin is at maximum strength in terms of lowering blood glucose.
Duration is how insulin continues to lower blood glucose.
Insulin Strength

All insulins come dissolved or suspended in liquids. However, the solutions have different strengths. The most commonly used strength in the United States today is U-100. That means it has 100 units of insulin per milliliter of fluid. U40, which has 40 units of insulin per milliliter of fluid, is not used in the U.S., but is still used in Europe and in Latin America. If you're traveling outside of the U.S., be certain to match your insulin strength with the correct size syringe.

Insulin Additives

All insulins have added ingredients. These prevent bacteria from growing and help maintain a neutral balance between acids and bases. In addition, intermediate and long-acting insulins also contain ingredients that prolong their actions. In some rare cases, the additives can bring on an allergic reaction.

Animal Insulins

For many years, the insulin used by people with diabetes was produced from the pancreases of pigs and cows. Synthetic human insulin derived from genetically engineered bacteria first became available in the 1980s, and now all insulin available in the United States is manufactured in a laboratory. Although the development of synthetic human insulin was a boon for most people, especially those who were allergic to the animal insulins, a few people find that they can manage their diabetes better using animal insulins.