Pharmacology, part 29: Musculoskeletal Medications for Osteoporosis
by Cathy Parkes March 25, 2021 Updated: February 04, 2022 8 min read
In this article, we cover the most important medications you need to know for osteoporosis, including bisphosphonates, selective estrogen receptor modulators, and a hypocalcemic agent. We'll start with some background on osteoporosis, including its pathophysiology.
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!
Osteoporosis is a metabolic bone disorder that causes a lack of bone mass, leading to fragile bones and an increased risk of fractures.
If you'd like to learn more about osteoporosis, check out our Medical-Surgical flashcards for nursing students — osteoporosis is one of the musculoskeletal disorders covered, along with its pathophysiology, risk factors, signs/symptoms, diagnostics, treatment, and patient teaching; as well as an A&P refresher on bones in general.
Our bones have a process to maintain homeostasis called bone remodeling, and it involves bone cells called osteoblasts and osteoclasts.
Osteoblasts vs. osteoclasts
Osteoblasts build bones, while osteoclasts break down bones.
Osteoporosis happens when the rate of bone resorption (breakdown) by osteoclasts exceeds the rate of bone formation by osteoblasts.
Postmenopausal osteoporosis is the most common type of osteoporosis. Estrogen helps to stimulate bone growth and reduce the activity of osteoclasts, but a patient's estrogen levels drop precipitously when they hit menopause.
Bisphosphonates - Alendronate (Fosamax)
Alendronate (Fosamax) is a bisphosphonate that can be used for postmenopausal osteoporosis as well as Paget's disease of the bone,* which is a metabolic disorder that causes bones to be soft, structurally disorganized, and weak.
*There are at least 4 different Paget's diseases named after a 19th century doctor James Paget. In this video, Cathy says that Paget's disease is "a rare form of breast cancer," which is technically also true—but Alendronate, because it is an osteoclast inhibitor for bones, is used for Paget's disease of the bone, NOT Paget's disease of the breast. Whoops!
Mode of action
The mode of action of alendronate, along with other medications in the bisphosphonate class, is to prevent bone resorption by inhibiting the activity of osteoclasts. Remember that osteoclasts break down bones and take calcium from the bone into the bloodstream, and in the case of osteoporosis, osteoclasts are too active. Inhibiting osteoclasts helps to prevent further bone breakdown.
Alendronate's most important side effect to be aware of is esophagitis: inflammation of the esophagus which can cause pain, difficulty swallowing, and chest pain. Other side effects include GI upset, muscle pain, and visual disturbances.
Alen drones on and on about his esophagitis.
Why can alendronate cause esophagitis?
The actual pill of Alendronate (and other bisphosphonate medications) can act as a local irritant to the gastrointestinal tract. It is hypothesized that bisphosphonates compromise the mucosal barrier, which can allow gastric acid through the epithelial lining, causing pain or a burning sensation. The patient teaching tips that follow help reduce the risk of esophagitis.
Key patient teaching points for alendronate include the following.
- Patients should take alendronate on an empty stomach in the morning with a full glass of water.
- After taking alendronate, patients should sit upright or ambulate for at least 30 minutes to prevent esophageal ulceration—no lying down!
- Patients should increase their intake of calcium and vitamin D. Vitamin D is required for calcium absorption.
- Patients should engage in weight-bearing exercises to help preserve their bone mass.
- Patients' bone density should be monitored closely during therapy.
Selective estrogen receptor modulator - Raloxifene (Evista)
Raloxifene (Evista) is a selective estrogen receptor modulator used for postmenopausal osteoporosis. Raloxifene can also help reduce the risk for breast cancer.
Raloxifene helps “fix” osteoporosis (fix is spelled backwards).
Mode of action
Raloxifene's mode of action is to bind to estrogen receptors, which decreases bone resorption.
A selective receptor modulator is a drug that has different effects in different tissues. Raloxifene is unique because when it binds to estrogen receptors, it can reproduce the beneficial effects of estrogen in the bones (promoting bone growth and bone density maintenance) without the negative effects of estrogen on breast or endometrial tissue.
Another medication in this class is tamoxifen, used for breast cancer.
Side effects of raloxifene include an increased risk of embolic events (blood clots), like a pulmonary embolism, deep vein thrombosis, or stroke. Raloxifene can also cause hot flashes or leg cramps.
Black box warning
Raloxifene carries a black box warning due to its risk of causing blood clots.
If you have a patient taking raloxifene, encourage them to increase their intake of calcium and vitamin D, and to do weight-bearing exercises.
If you have a patient taking raloxifene, remember to monitor their bone density.
Hypocalcemic agent - Calcitonin (Miacalcin)
Calcitonin is a naturally-occurring hormone secreted by the thyroid that decreases blood calcium levels. The manufactured form of calcitonin (Miacalcin) is a hypocalcemic agent used for postmenopausal osteoporosis, as well as hypercalcemia.
Hypercalcemia is seen in hyperparathyroidism, which is a disorder of the parathyroid glands resulting in hypersecretion, or excess secretion, of parathyroid hormone (PTH) resulting in excess blood calcium levels. Hyperparathyroidism is one of the important disorders covered in our Medical-Surgical flashcards.
Tonin = Tone it down! (i.e. lowers calcium levels in the blood).
Mode of action
Calcitonin's mode of action is to prevent bone resorption by inhibiting the activity of osteoclasts. Remember that osteoclasts' primary job is to break down bone, so to retain bone density, we want to inhibit those osteoclasts. Calcitonin also increases renal excretion of calcium.
Side effects of calcitonin include GI upset, which is very common, and if administered intranasally, nasal irritation or dryness.
The patient teaching tips you need to remember with calcitonin are the same tips with the other osteoporosis medications we've covered here.
- Patients should be getting adequate calcium and vitamin D in their diet or through supplements.
- Patients should do weight bearing exercises.
If you have a patient taking calcitonin, it is important to monitor their bone density.
Okay, in this video we are going to continue with our coverage of key musculoskeletal medications that you should know. And specifically in this video, we will be covering medications used for osteoporosis. If you are following along with your cards, I am on card 93 in our Pharmacology Flashcards edition 2.0.
Okay, so let's talk about first medication class which are bisphosphonates. And the key medication that falls within this class in alendronate.
Alendronate can be used for postmenopausal osteoporosis as well as Paget's disease, which is a rare form of breast cancer.
The mode of action of alendronate is to prevent bone resorption by inhibiting the activity of osteoclasts. So normally, osteoclasts are breaking down the bone and taking calcium from the bone into the bloodstream. And we don't want that, right? We want that calcium to stay in the bones. So that's what alendronate helps to do, right? It prevents the osteoclasts from breaking it down, so we are keeping that calcium in the bones.
In terms of the side effects, the key side effect that's going to be important for you to remember is esophagitis. So this is where we have inflammation of the esophagus. Other side effects include GI upset, muscle pain and visual disturbances.
There are some key teaching points that you need to provide your patient and they are listed on this card here, card 93 in bold and red. So definitely review those things.
We want to advise our patient to take this on an empty stomach in the morning with a full glass of water, and then after they take this medication, we do not want the patient lying down because that can really result in that esophagitis. So after they take this medication, they need to sit upright or ambulate for 30 minutes to prevent that esophageal ulceration that can occur. So that's going to be very important.
Also we're going to want to encourage our patient to increase their intake of calcium and vitamin D, because vitamin D is needed for calcium absorption and they should also engage in weight-bearing exercises to help preserve their bone mass. And then we're going to want to monitor their bone density regularly during therapy.
So my little trick for remembering this, if you look at the word alendronate, I think alen, some guy name Alan drones on and on about his esophagitis. The other little trick that you might use to remember this is after you take your alendronate, maybe go out and fly your drone, right? Like you're usually standing up when you fly your drone. Maybe you're sitting up but usually not laying down flying your drone, right? So if you fly your drone for 30 minutes after you take alendronate, then that will help prevent that esophageal ulceration.
Right. Now let's talk about a selective estrogen receptor modulator which is raloxifene. So raloxifene is used for post-menopausal osteoporosis. It can also help reduce the risk for breast cancer.
The mode of action is that it binds estrogen receptors which decreases bone resorption.
In terms of the side effects, the key side effect I would remember includes an increased risk for embolic events. So this includes things like a DVT, a PE, or a stroke. This medication does carry a black box warning for just this reason because of the increased risk for clots. In addition, hot flashes and leg cramps are also common.
For teaching, you want to make sure your patient is increasing their intake of calcium and vitamin D, and we want to encourage weight-bearing exercises as well.
And then we want to monitor the patient's bone density.
In terms of how I remember this medication, if you look at the name raloxifene, and you look at it backwards, it has fix and then the letter O. So I think that raloxifene will fix your osteoporosis. So it's kind of spelled backwards there, and that helps me to remember what it's for.
Okay. Finally, let's talk about a hypocalcemic agent, meaning an agent that helps to bring down calcium levels in the blood. So the medication that falls within this class is calcitonin.
Calcitonin is used for post-menopausal osteoporosis as well as hypercalcemia, meaning we have too much calcium in the bloodstream.
It works to prevent bone resorption by inhibiting the activity of osteoclasts. It also increases renal excretion of calcium.
In terms of the side effects, GI upset is common and if you are taking it through the intranasal route, then nasal irritation or dryness is also common.
In terms of teaching, we're going to do the same type of teaching. Make sure you're getting enough calcium and vitamin D, weight-bearing exercises, and monitoring the patient's bone density will be important.
In terms of how I remember this medication, if you look at the word calcitonin, you think ‘tone it down,’ meaning tone down that calcium. Bring those calcium levels down in the bloodstream.
So that is it for our osteoporosis medications. In my next video, we will cover medications for gout. So hang in there with me and we'll get through these meds together!
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