Symlin, An Injectable Form of Amylin
Used to Improve Post Meal Glucose Control (Type 1) and Weight Loss (Type 1 and possibly Type 2)
During the destruction of beta cells in Type 1 or Type 1.5 diabetes by friendly fire from antibodies, the body actually loses two hormones. And similar to insulin, Amylin production may fall in Type 2 diabetes over time. Amylin is normally co-secreted alongside insulin and, like insulin, is released by the beta cells around the clock with larger amounts released at mealtimes.
Insulin was the first of the two hormones to be discovered because it was so critical to survival. It was not until 1970 that amylin was discovered, and not until the early 1990s is that its role began to be understood. Not essential for life, amylin plays an important role in glucose regulation by slowing digestion and suppressing an excessive release of glucagon that is seen after meals in Type 1 diabetes. The excess glucagon rise seen in Type 1 diabetes causes additional glucose release by the liver at mealtimes. The release of amylin at mealtimes minimizes the glucose spikes that are often seen in Type 1 diabetes after meals.
Symlin is a modified longer-acting form of amylin that was released by the FDA in 2005. This prescription medication dramatically improves post meal glucose control and reduces glucose variability and glucose exposure in anyone whose insulin production is limited. Symlin decreases glucagon secretion, decreases appetite, and delays gastric emptying. When injected before meals, post meal blood sugars become easier to control. Users often comment that they feel better with more stable glucose readings.
One caution when starting on Symlin is that it can cause severe low blood sugars if meal insulin doses are not lowered on the day it is started and for at least the first few days of use. If meal insulin doses are not reduced, up to 30% of users experience severe hypoglycemia within about 3 hours of eating. To reduce the risk of hypoglycemia, Symlin is started at very small doses and then gradually increased every few days until the desired effect is seen. Meal insulin doses are typically reduced by 30% to 50% when starting and later adjusted based on pre and post meal glucose results once a final Symlin dose is reached. Long-acting insulin doses or basal rates may also need to be lowered, especially if these make up more then 50% of the starting TDD (total daily dose of insulin). As weight loss occurs in someone who is overweight, additional insulin reductions will be needed over time.
Dosing
Symlin is injected with a standard insulin syringe, so dosing is flexible. How much to use depends on what it is used for. For weight loss, maximum doses are usually best, while lower doses often work when the goal is to normalize post-meal glucose levels. The manufacturer recommends starting with 2.5 units and increasing to 5 units, then 7.5 units, and 10 units before each meal if no nausea is encountered for three days.
However, different people will require very different doses and we recommend that Symlin doses be individualized in the same way as insulin doses. If your goal is to reduce post meal spiking and glucose variability, raise the Symlin dose by one unit every three days until you reach a dose where most of your post meal blood sugar readings rise no more than 40 to 60 mg/dl (2.2 to 3.3 mmol) above where they started. The idea is to take enough to have good post meal control (less variability) without overly delaying the normal rise in glucose after a meal (less problem correcting a low reading). Keep raising the Symlin or increasing meal boluses until post meal readings are consistently less than 60 mg/dl (3.3 mmol) higher than the premeal readings. The correct doses of Symlin and insulin allow you to keep most post meal readings from rising much while causing few lows. In many Type 1s, only 2 to 6 units taken two or three times a day before meals are required to do this. Symlin is usually taken just before meals that contain at least 250 calories or 30 grams of carbohydrate. If a dose is missed, wait until the next meal to take the regular scheduled dose.
Your current TDD for insulin can guide your premeal Symlin dose. Approximately 10% of your insulin TDD is needed as Symlin before each meal. For instance, if you use 40 units of insulin a day you will need approximately 4 units of Symlin before each meal to control your post meal readings. For weight loss, of course, larger amounts will be needed. A safer way to increase Symlin is to start with 2 units before two or three meals a day, or 1 unit if your TDD is less than 30 units of insulin a day. Increase by 1 unit per meal every three days as long as nausea is not present.
Post meal Control
Glucose spiking after meals can be totally eliminated at higher doses, with flat glucose trend lines often seen on a continuous monitor. At higher Symlin doses, however, if a large carb meal is consumed, the rise in the blood sugar may not be seen until several hours later, such as a high reading at breakfast the next morning after a large carb intake at dinner. Matching injected insulin doses to Symlin can be difficult. Today's rapid insulins become too fast when larger doses of Symlin are used. If you inject your insulin, the use of a slower insulin like Regular may be preferred.
On a pump, a combo bolus (some now, the rest over time) or an extended bolus can be used to match the slower rise in glucose after meals. If a blood sugar is low before a meal, raise it before taking Symlin. Reduce the meal bolus and give it as an extended bolus. If Symlin doses are missed for more than two or three days, do not restart with full doses. Instead, restart at a lower dose and build up to lessen the risk of hypoglycemia.
Weight Loss
Less hunger allows some people who are overweight to lose significant amounts of weight, while normal weight individuals lose none. Symlin is currently undergoing studies for approval by the FDA as a weight loss drug.
For weight loss, the dose may occasionally need to go higher.
Stability
Symlin is less stable than insulin. If one bottle of Symlin appears to have no effect on your blood sugar try another bottle. Symlin activity is more vulnerable to time and temperature than insulin and can lose significant activity, especially if a sample bottle was handed out from a physician's office. If you seem to get little effect from a bottle, start a fresh bottle at a lower dose. Excess doses are easy to spot by a feeling of fullness or nausea after the dose is given. Vomiting and diarrhea may occur on an excessive dose. If side effects occur, simply lower the dose by one or 2 units. Increase the dose again after there is no fullness or nausea for at least three days.
Tips On Handling Lows
Symlin delays the digestion of all food, including the carbs you use to raise a low blood sugar. If a low occurs, use glucose tablets if available and chew them as long as possible to allow more glucose to be absorbed directly into the bloodstream. Be patient, as the rise in your glucose will be slowed because of Symlin. Likewise when lowering a high reading with insulin, it will take longer and may require larger than normal insulin doses because food is still being absorbed.
The Symlin Pen
The FDA approved pre-filled Symlin pens in November of 2007 and Amylin made them available in January of 2008. Previously, it was only available in vials. There are currently two pens available: the SymlinPen 60 and 120. The SymlinPen 60 delivers 15, 30, 45, or 60 micrograms per dose. The SymlinPen 120 delivers 60 or 120 micrograms per dose. Both may be stored at room temperature, up to 86 degrees, after first use.
Summary
Even though Symlin affects the blood sugar, it does not control it. Your carb boluses and basal rates must still be adjusted to match the carb amounts and types that you eat. Once an effective dose of Symlin is found, adjust your insulin doses or boluses and basal rates as needed and be prepared to readjust periodically if you are also losing weight.
Symlin, An Injectable Form of Amylin
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