Pharmacology, part 32: Endocrine Medications - Oral Antidiabetics: Sulfonylureas, Meglitinides, Biguanides
September 06, 2021 Updated: December 29, 2021 9 min read 1 Comment
Why do sulfonylureas make patients get a sunburn? Why should you discontinue metformin before getting a contrast X-ray? In this article we'll answer these intriguing questions and more!
Here we've explained 3 of the 4 classes of key antidiabetic meds you need to know to be successful on the NCLEX: sulfonylureas, meglitinides, and biguanides. We'll start by giving you a quick review of diabetes and explain who can take oral antidiabetics and why. Then we'll cover the modes of action, side effects, contraindications and patient teaching for sulfonylureas, repaglinide and metformin.
The Nursing Pharmacology video series follows along with our Pharmacology Flashcards, which are intended to help RN and PN nursing students study for nursing school exams, including the ATI, HESI, and NCLEX.
When you see this Cool Chicken, that indicates one of Cathy's silly mnemonics to help you remember. The Cool Chicken hints in these articles are just a taste of what's available across our Level Up RN Flashcards for nursing students!
Insulin is a hormone made naturally in the body that plays a key part in keeping us alive. Insulin’s job is to transport glucose (sugar) from the bloodstream into the body’s cells where it can be used for energy.
Diabetes causes chronic hyperglycemia (increased blood sugar levels) due to EITHER:
- insufficient insulin production by the pancreas (type 1 diabetes)
- or insulin resistance of the cells in the body (type 2 diabetes).
Learn more about diabetes
You need to learn about diabetes in depth to be successful on your nursing school exams and in your career, because it's one of the most prevalent diseases in America, with 13% of US adults having it (CDC, 2020).
We cover diabetes in more depth in our Medical-Surgical Nursing Flashcards and in our accompanying free article Med-Surg Endocrine System Part 18: Diabetes Mellitus.
Who can take oral antidiabetic agents?
Oral antidiabetic agents are only for people with type 2 diabetes.
Oral antidiabetics aren’t insulin replacements; they are more like insulin encouragers. This means that these medications don’t work for type 1 diabetics, because their insulin cannot be encouraged. They simply can’t make it, and require outside insulin. Patients with type 2 diabetes can be given insulin or oral antidiabetic agents.
Key side effect of oral antidiabetic agents
A key side effect of oral antidiabetic medications is hypoglycemia, which is low blood sugar .
If you have been following along with this series or know your meds, you may remember that with blood pressure medications, if a dose is too high, the blood pressure can be lowered too much and result in hypotension.
The same principle is true here. Oral antidiabetic medications are meant to lower blood sugar. If the meds do their job too well, or the patient receives too high a dose, they can end up with hypoglycemia.
Sulfonylureas: glipizide (Glucotrol), glyburide (Diabeta)
Sulfonylureas are a class of oral antidiabetic medications that includes glipizide and glyburide. Patients with type 2 diabetes may be prescribed sulfonylureas to keep their blood sugar down.
Glipizide/glyburide - think of gleefully riding down a slide (with blood sugars coming down).
Taking sulfonylureas is contraindicated for people who have a sulfa allergy.
What is sulfa?
Sulfonamide is a chemical group. Drugs made from this chemical group are called sulfonamides or sulfas; most commonly these are antibiotics.
One example of a sulfonamide antibiotic is trimethoprim/sulfamethoxazole, which is covered in the immune system section of this Pharmacology series.
Sulfonylureas mode of action
Sulfonylureas work to bring a patient's blood sugar levels down by increasing the release of insulin from the pancreas.
Sulfonylureas side effects
Side effects of sulfonylureas include photosensitivity, GI upset, and hypoglycemia, like we talked about.
Signs and symptoms of hypoglycemia include tachycardia, diaphoresis, shakiness, headache, and weakness.
Why do sulfonylureas cause photosensitivity?
Sulfonylureas may cause photosensitivity because their chemical structure (sulfonamide, which we mentioned earlier) is known to be photoactive, which means capable of a chemical or physical change in response to light.
When the light from UV rays hits you, the drug in your body absorbs it, its chemical structure changes slightly and becomes less stable, which causes the skin to react and become inflamed.
Sulfonylureas patient teaching
Advise patients to take a sulfonylurea medication 30 minutes before a meal.
Patients definitely need to wear sunscreen when they go outside because of the side effect of photosensitivity. Sunscreen blocks UV rays so it can prevent the photoactivity reaction from occuring.
Patients taking sulfonylureas should not drink alcohol because it can lead to hypoglycemia.
Meglitinides: repaglinide (Prandin)
The next category of oral antidiabetics you'll need to know are meglitinides. A key medication that falls within this class is repaglinide. They both end in "-inide"! Repaglinide is taken by patients with type 2 diabetes to lower blood sugar.
Repaglinide mode of action
Meglitinides like repaglinide have essentially the same mode of action as sulfonylureas: they help to increase insulin release from the pancreas.
Repaglinide side effects
Side effects of repaglinide can include the hypoglycemia we discussed previously, as well as angina.
We cover angina in the cardiovascular system section of our Medical-Surgical Nursing Flashcards.
Repaglinide patient teaching
When it comes to patient teaching for repaglinide, advise your patient to take this medication three times a day, and to eat within 30 minutes of taking the medication.
Biguanides: metformin (Glucophage)
The final oral antidiabetic class we'll cover in this article are biguanides, which include the common drug Metformin. Metformin is a drug commonly taken by patients with type 2 diabetes to lower blood sugar.
Metformin mode of action
Metformin works by decreasing glucose production in the liver, and increasing the uptake of glucose by the body cells.
Metformin side effects
Side effects of metformin can include GI upset, a metallic taste, as well as lactic acidosis.
Lactic acidosis is a form of metabolic acidosis marked by lactic acid buildup in the bloodstream. The signs and symptoms of lactic acidosis include diarrhea, dizziness, hypotension, weakness, and bradycardia.
A construction foreman (who takes metformin) drinks out of his metal thermos, then gets GI upset, a metal taste, and lactic acidosis.
Metformin patient teaching
Patients taking metformin should take it with a meal.
They should not use alcohol, because it may cause hypoglycemia.
If a patient who is taking metformin gets scheduled for a procedure that will require them to be NPO (not eat) or a procedure that requires contrast dye, they should discontinue metformin 48 hours prior to that procedure.
The reason why is because if they are not eating any food, they are not getting any glucose, and so continuing to take metformin would put them into a hypoglycemic state.
Contrast dye used for X-rays may impair function in the kidneys for a small percentage of patients. Metformin may cause lactic acid buildup in patients with impaired kidney function, so that's why the two are not recommended together.
Patients may need to take a B12 supplement if it is indicated; metformin has been correlated with B12 deficiencies. B12 and the other B vitamins are covered in our Nutrition Essentials for Nursing Flashcards.
In our next article we'll cover another oral antidiabetic— thiazolidinediones!
Hi. I'm Cathy with LevelUp RN. In this video, I am going to cover some oral antidiabetic agents. And if you have our pharmacology second edition flashcards, definitely pull those out so you can follow along with me. And at the end of the video, I'm going to provide a little quiz to test your knowledge of some of the key points that I'll be covering in this video. So definitely stay tuned for that.
Also, it is very likely there will be a blooper reel at the end of this video because I will be pronouncing some of the oral antidiabetic medication class names, which are exceptionally challenging for me. So thank you for your patience. And if you are in need of a good laugh, then definitely stay tuned for those bloopers at the end of the video.
Okay, a couple of other things I want to mention before I get into specific classes is that oral antidiabetic agents are just for type 2 diabetes. So if a patient has type 1 diabetes, they are insulin-dependent, so they will just get insulin. For patients with type 2 diabetes, they can be given insulin or oral antidiabetic agents. So that's definitely important to know.
The other thing I wanted to mention is that with a lot of these oral antidiabetic agents, a key side effect of these medications will be hypoglycemia. So just like with blood pressure medications, if the dose is too high, that blood pressure can come down too low. We can end up with hypotension. With these oral antidiabetic medications, their job is to bring blood sugar levels down. If they do their job too well, or we give the patient too high of a dose, we can end up with hypoglycemia, which definitely makes sense.
All right, so the first drug class I want to talk about here are sulfonylureas.
And medications that fall within this class include glipizide and glyburide.
These medications help to bring a patient's blood sugar levels down by increasing the release of insulin from the pancreas.
A contraindication of this drug class would be a sulfa allergy.
And side effects of this drug class include hypoglycemia, like we talked about.
So signs and symptoms of hypoglycemia include tachycardia, diaphoresis, shakiness, headache, and weakness. Other side effects can include photosensitivity and GI upset.
In terms of patient teaching, we want to advise our patient to take this medication 30 minutes before a meal. They should not use alcohol. And they definitely need to wear sunscreen when they go outside because of that side effect of photosensitivity.
So our cool chicken hint for this card, which you can find here at the top of the card, is when you look at the drug names glipizide and glyburide, it makes me think of riding or sliding down a slide. So that helps me to remember that you're going down the slide, and blood sugar levels are coming down with you. Also, slides are often in playgrounds outside. So when I think about being outside, I think about the sun being above me, and that helps me to remember photosensitivity as a side effect of this medication cause as well.
Next up, we have our meglitinides.
And a key medication that falls within this class is repaglinide.
This medication class has essentially the same mode of action as the sulfonylureas. So they help to increase insulin release from the pancreas.
Side effects include hypoglycemia again, as well as angina.
And then in terms of patient teaching, you want to advise your patient to take this medication three times a day, and eat within 30 minutes of taking the medication.
So the way I remember this medication, if you look at the drug name repaglinide, that pag, P-A-G, reminds me of a pageant. So I think of a woman who is about to compete in a pageant, and she's about to go out on stage, but she has like chest pain, and she's feeling dizzy. She has diaphoresis and is weak. And she's attributing all of these signs and symptoms to being nervous about going on stage for this pageant. But in reality, she just started taking repaglinide, and it's actually her medication that is causing that angina, as well as the symptoms of hypoglycemia.
All right. Next, we have our biguanides, which includes a medication metformin.
This medication class works by decreasing glucose production in the liver, and increasing the uptake of glucose by the body cells.
Side effects can include GI upset, a metallic taste, as well as lactic acidosis.
And the signs and symptoms of lactic acidosis include diarrhea, dizziness, hypotension, weakness, and bradycardia.
In terms of patient teaching that you need to provide for a patient who takes metformin, they should take this medication with a meal. They should not use alcohol. And if they are scheduled for a procedure that will require them to be NPO or a procedure that requires contrast dye, we need to discontinue metformin 48 hours prior to that procedure.
So my little cool chicken hint for remembering some of the key side effects of metformin, is if you look at the word metformin, you got formin as part of that. So I imagine a foreman going to a construction site with his metal thermos. And as he's drinking from his thermos, he has like a metallic taste. He's like, oh, this doesn't taste good. And suddenly he feels really bad too. He has diarrhea. He feels weak. He feels dizzy. And he's chalking it up to this new thermos that he bought, when in actuality it is his metformin medication that he just started taking for type 2 diabetes that is causing that metallic taste, and causing those signs and symptoms of lactic acidosis, which include GI upset, diarrhea, weakness, and dizziness.
Okay. Time for quiz. I have three questions for you. First question, oral antidiabetics can be used with both type 1 and type 2 diabetes, true or false? The answer is false. So oral antidiabetic agents should only be used with patients with type 2 diabetes. Patients with type 1 diabetes will require insulin. Second question, what is a key side effect of many oral antidiabetic agents? If you said hypoglycemia, you are correct. Third question, what oral antidiabetic agent carries a risk for lactic acidosis? The answer is metformin.
Okay. I hope this quiz has been helpful. If you would like to see more quizzes at the end of my videos, definitely leave me a comment, and be sure to like this video as well. Take care and good luck studying.
Blooper Reel: Next up, we have our gluta-- I'm sorry. Has essentially the same mode of action as the sulfonylureas. Essentially the same mode of action as the sulfonylureas.
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