Byetta and Bydureon

A quick trivia question: which medication used for type 2 diabetes is a synthetic version of a protein found in the saliva of the venomous Gila monster?  (I would put up a picture of one of these guys, but they are a bit frightening if you are not a fan of lizards and such).  Read on to find out the answer…

Dr K. here, your virtual pharmacist.  Today I will be talking about a medication that is used for type 2 diabetes that is available only as an injection.  When you think about injecting something for diabetes, I’m sure insulin comes to mind.  But did you know there are other injectable diabetes medications that are not insulin?  Today I will tell you about one of these: Byetta.  The generic name for Byetta is exenatide, but it is currently only available as brand name Byetta or Bydureon (a longer lasting form of exenatide).  And yes, Byetta is a synthetic form of a protein that exists in the saliva of a Gila monster, a protein that helps them to only eat four times a year!

How does it lower blood sugar: Byetta is in a class of medications known as incretin mimetics.  What does this mean in plain English?  Well in simple terms, Byetta helps insulin work better in your body.  Remember, insulin is the hormone that helps to move glucose into the cells and out of the blood.  Byetta does this by mimicking, or “acting like,” a hormone in the body called GLP-1.  So let’s see what GLP-1, and therefore Byetta, can do for you!

GLP-1 is a very important hormone that helps to lower your blood sugar, and it does this in a wide variety of ways.  First, GLP-1 increases the amount of insulin released from your pancreas when your blood sugars are high.  GLP-1 increases the size of your beta cells, the cells that are responsible for storing and releasing insulin.  Also, GLP-1 makes the cells in your body more sensitive to insulin, meaning more glucose can get out of the blood and into the cells.

There are many more ways that GLP-1 works in your body.  For instance, it slows down something that we call “gastric emptying,” which is a fancy term for the amount of time it takes for food that you’ve eaten to leave the stomach.  Why is this important?  Well, the faster the food leaves your stomach, the faster the carbohydrates you’ve eaten can be absorbed, which leads to a spike in your blood sugar.  GLP-1 slows down this process so that the spike that you usually have after you eat will be later than normal.  As I will talk about later, this can lead to some side effects.

Glucagon is a hormone in your body that works in the opposite way as insulin – it helps to raise your blood sugars when they are low.  Obviously we don’t want too much glucagon working in your body though if you are trying to keep your blood sugars down.  GLP-1 helps to control this by decreasing the amount of glucagon that your pancreas releases, which keeps your blood sugars at a healthier level.  And another exciting thing about GLP-1: it actually helps you eat less by making your body feel full!  Wouldn’t we all like a lot more GLP-1 in our lives?!

The effect on your numbers: You can expect Byetta to lower your A1c by about 0.5 to 1% (so if your starting A1c was 8, it could go down to 7.5 or 7 after being on Byetta).  Remember how I told you that Byetta will help you eat less?  Well, this can lead to weight loss.  The makers of Byetta state that patients have been shown to lose about 4 pounds in 30 weeks when on Byetta and certain other diabetes medications.  Some patients report having lost more weight, and others none at all, so don’t expect Byetta to be a magical weight loss potion.

Dosing: Patients are usually started on 5 mcg of Byetta, injected twice daily.  Byetta should be injected within 60 minutes before the morning and evening meal, never after the meal.  It is important to always eat after you’ve taken Byetta so that you do not develop hypoglycemia (dangerously low blood sugars).  If you forget to take Byetta and then eat a meal, skip that dose and wait to inject at the next scheduled dose.  Never inject two doses to make up for a dose that you missed.  Do not take Byetta if you are not going to eat in the next 60 minutes.

After a month of being on Byetta, your dose can be increased to 10 mcg twice daily, if your doctor okays it.  You should start seeing a decrease in your blood sugar levels soon after starting Byetta; it does not take a month, but we wait a month to increase the dose so that your body can adjust to the stomach upset that is common with Byetta.

Bydureon is a longer-acting form of Byetta that is available as an injection.  The dose for Bydureon is 2 mg injected only once a week.  The benefit of once weekly dosing is that there is less stomach upset than there is with twice-daily Byetta.  I will discuss this side effect and more in a little bit.

Byetta and Bydureon can be injected into the stomach, thigh, or back of the upper arm.  We are injecting into the fat cells, not the muscle or vein.  You can use the same part of the body each time to inject, but try to rotate locations on that part of the body to avoid scarring that will affect how the drug is absorbed into your body.

Unused Byetta and Bydureon should be stored in a refrigerator until the first usage.  Once used, they can be stored at controlled room temperature for up to four weeks.  You must discard any unused portion of the medication 30 days after it has been opened.

Side effects: The most common side effect of Byetta is nausea, which is seen in up to 44% of patients.  This can be accompanied by diarrhea (up to 20% of patients), constipation (10%), and vomiting (18%).  These are probably due in part to the increased amount of time that food is sitting in the stomach that we discussed earlier.  Patients on Bydureon will experience less of these side effects.  Related to the injection of the medication, you might experience pain or itching at the injection site (about 18% of patients) or a small lump at the injection site (about 5-10% of patients).  Some other side effects include headache and feeling jittery or nervous.

Currently there are trials and investigations as to whether or not Byetta and Bydureon cause pancreatitis (inflammation of the pancreas) or pancreatic cancer.  A study published earlier this year in the Journal of the American Medical Association found that diabetic patients admitted to the hospital with pancreatitis were twice as likely to be on either Byetta or Januvia compared to diabetics without pancreatitis.  If you would like to read the official alert that the FDA has put out about this class of medications, you can read it here.

The other big side effect to watch out for is hypoglycemia, or low blood sugar.  This can be seen in up to 36% of patients.  It is important to know what things can make you more likely to experience these low blood sugars.  First, if you are on another medication that can cause hypoglycemia, such as sulfonylureas (glyburide, glipizide, glimpepiride), you are at a greater risk of having dangerously low blood sugars.  If you do not eat after taking Byetta, you are likely to develop hypoglycemia, which is why it is crucial that you eat within 60 minutes of injection.

Who should not take Byetta: Byetta is not a substitute for insulin in patients with type 1 diabetes.  If you are a patient who struggles with episodes of hypoglycemia, and especially if you are unable to detect them in yourself, Byetta might not be the best medication for you.  Byetta should not be used in patients with severe kidney impairment or end-stage kidney disease.  If you have severe gastrointestinal disease or gastroparesis (already slow gastric emptying), you should not take Byetta.  If you are pregnant, you and your doctor should weigh the risks versus benefits of using Byetta (it is not the first medication of choice in pregnancy).  It is thought that Byetta might cause potential harm to a nursing infant, so talk to your doctor before you plan to breastfeed if you are taking Byetta or Bydureon.

Drug interactions: Byetta can affect how other medications are processed by your body.  If you are on oral birth control or antibiotics you should take them at least an hour before or two hours after injecting Byetta.  Byetta can also increase your INR if you are taking the blood thinner warfarin, so be sure that your doctor is aware that you are on warfarin so that they can make the right decision for you.  Tylenol and the cholesterol medication lovastatin might not work as well if they are taken with Byetta.  Thyroid medications might affect how well Byetta works.  These are only a few of the more common drug interactions with Byetta.  Please discuss the medications you are taking with your doctor or pharmacist before starting any new medications.

Monitoring: As always, you should continue to monitor your daily blood sugars and have regular A1c checks when on Byetta, or any other diabetes medication.  Watch for signs and symptoms of low blood sugars.  Also, monitor your weight with Byetta, since it can cause weight loss.

Place in therapy for diabetes: Byetta is generally seen as a medication that is used after patients do not have the desired A1c after trying metformin, a sulfonylurea like glipizide or glimepiride, or a combination.  In 2009 the FDA approved Byetta to be used alone, with diet and exercise only, for treatment of type 2 diabetes.  However, it can also be used in combination with other diabetes medications.

If you would like to learn more about Byetta you can visit the official website here.  And the official website for Bydureon is here.

As a disclaimer, I am your “virtual” pharmacist, here to provide you with information and answers to questions.  However, I am not your local pharmacist and could, in no way, be aware of your specific medical needs.  Remember to always check with your medical provider and pharmacist before stopping or starting any new medications.  My posts are based on general pharmacy principles and should not considered as your “first opinion” when it comes to your health.  Please consult with your doctor and pharmacist about anything regarding your health.

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