7 Alendronate (Fosamax) Side Effects You Should Know About

Alendronate (Fosamax) is in a class of prescription medications called bisphosphonates. Since they work to strengthen bones, these medications are most often used to prevent and treat osteoporosis (bone loss). But they can also be used for other bone-related conditions, such as Paget’s disease. 

Supporting your bone health helps prevent pain and fractures, but there can be some unintended side effects. If you’re wondering what side effects can happen when you’re taking alendronate, we’ve got you covered.

Alendronate side effects at a glance

The most common alendronate side effects are stomach-related. But more serious side effects are also possible. Below is a list of alendronate side effects reported during clinical studies. Keep in mind that not every possible side effect is listed here. Reach out to a healthcare professional if you have questions about possible alendronate side effects.

Common side effects:

• Stomach pain

• Acid reflux

• Constipation

• Diarrhea

• Heartburn

• Nausea

• Passing gas

• Headache

• Dizziness

• Bone pain

• Joint pain

• Muscle pain

• Lower calcium and phosphorous levels

Rare but serious side effects:

• Esophageal ulcers

• Severe bone, joint, or muscle pain

• Vision problems

• Osteonecrosis of the jaw

• Higher risk of femur fractures

• Allergic reactions (hives, itching, trouble breathing)

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Let’s take a look at seven notable alendronate side effects in greater detail. Knowing what to expect, how to manage them, and when to seek medical care can help you get the most out of your medication.

1. Nausea and heartburn

Nausea and heartburn are common alendronate side effects. That’s because it can irritate your throat and stomach lining after you swallow it. But don’t try taking it with food to avoid this side effect. Food will make it hard for your body to absorb the medication properly.

Instead, you should take alendronate first thing in the morning, at least 30 minutes before eating, drinking, or taking other medications. You should also take it with 6 oz to 8 oz of plain water.

You shouldn’t lie down after taking alendronate until at least 30 minutes after your dose. If you can stay upright until after your first meal of the day, that’s even better. If you lie down too soon or without eating first, your risk of nausea and heartburn will go up. You could also raise the risk of damage to your throat — more on that later.

If you experience either of these side effects, it’s best to discuss it with your healthcare team. They can help make sure you’re taking alendronate safely.

2. Constipation or diarrhea

This one seems a bit contrary, but you may have either constipation or diarrhea when taking alendronate. 

You can help prevent constipation by staying active, eating fiber, and drinking plenty of water. If needed, you can also try over-the-counter (OTC) medications for constipation. 

For diarrhea, it’s also helpful to stay hydrated. If you need an OTC diarrhea treatment, loperamide (Imodium A-D) may be an option. Just be sure you’ve waited at least 30 minutes after taking alendronate before taking any OTC options for constipation or diarrhea.

If either of these side effects become bothersome or last longer than a couple of days, contact your prescriber. They can determine if there’s another reason for your symptoms and how best to resolve them. 

3. Joint, muscle, and bone pain

Alendronate can cause pain in your joints, muscles, and bones (musculoskeletal pain). This side effect can occur within one day to several months after starting alendronate treatment. It’s also more common in women who have gone through menopause. 

Musculoskeletal pain may be a simple inconvenience. If it’s short-term, you can often manage it with an OTC pain medication like acetaminophen (Tylenol). But if your pain is severe or doesn’t go away, be sure to let your prescriber know. Most people take alendronate to help prevent bone fractures. But there’s a small risk for thigh bone (femur) fractures when taking it, and severe or lingering pain could be a sign of a fracture.

4. Headache

Another common alendronate side effect is headaches. Keep in mind that headaches can also be caused by other factors, including stress, dehydration, and lack of sleep. 

There are several things you can do to get rid of a headache. Meditation, yoga, and exercise are some things that may help. Ask your pharmacist or prescriber if it’s okay for you to take an OTC pain reliever. And let them know if headaches worsen or aren’t relieved with OTC treatments. 

5. Ulcers in the esophagus

Alendronate can irritate and damage your digestive tract, causing esophageal ulcers. This is a wound that occurs in your esophagus (the tube between your throat and your stomach). An ulcer in your esophagus is a serious medical condition. 

The good news is there are a few simple, important steps you can take to help prevent this side effect. In addition to taking alendronate on an empty stomach, remember these two key points: 

1. Take alendronate with a 6 oz to 8 oz glass of plain water (no bubbles). And don’t chew or suck on the tablet — swallow it whole. This will help move the medication through your esophagus. 

2. Don’t lie down after taking alendronate. Stay upright, either sitting or standing, for at least 30 minutes. And don’t lie down after that until you’ve eaten something. This will help make sure the medication has moved through your body and won’t cause damage to your esophagus.

Symptoms of an ulcer in your esophagus include chest pain, severe heartburn, or pain when swallowing. Contact your prescriber immediately or seek emergency care if you have these symptoms.

Good to know: If you have difficulty swallowing pills, or they tend to stick in your throat, alendronate is not the best option for you. But, there are alternative treatments available. Check out our guide to choosing osteoporosis medications or talk to a healthcare professional for more information on your options.

6. Jawbone issues

Osteonecrosis of the jaw (ONJ) is a rare but serious condition that can happen when you take alendronate. It can lead to breakdown of the bone in your jaw, which can cause significant pain and swelling. But ONJ is only estimated to affect about 0.001% to 0.15% of people taking a bisphosphonate for osteoporosis. 

The risk of ONJ increases when people with dental problems take bisphosphonates. It can also happen if you take alendronate while receiving cancer treatment. Jawbone issues are often associated with a dental procedure or tooth infection. And the risk also goes up the longer you take alendronate. The best thing you can do to prevent this side effect is to take care of your teeth and gums. 

Report any unusual jaw swelling or pain to your prescriber as soon as possible. And let them know if you need invasive dental work. They may want to stop alendronate before your procedure to lower the risk of this side effect.

7. Eye problems

Alendronate may cause inflammation of the eye in rare cases. Symptoms may include blurry or double vision, sensitivity to light, and swelling of the eye. You may also experience eye pain. Contact a healthcare professional right away if you experience these symptoms.

When should you seek medical care for alendronate side effects?

Most alendronate side effects are mild. And taking it as directed can help prevent stomach-related issues. But if you’re concerned about any side effects you’re experiencing, contact your healthcare team. They can help you decide how best to manage them.

Seek immediate medical attention if you experience chest pain, trouble swallowing, or have severe pain. These could be symptoms of more serious side effects.

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Written by:

Brian Leonard, PharmD, BCACP, BCGP

Brian Leonard earned his doctorate in pharmacy from the University of Florida College of Pharmacy and is board certified in Ambulatory Care and Geriatric Pharmacy.

Edited by:

Stacia Woodcock, PharmD

Stacia Woodcock, PharmD, is a pharmacy editor for GoodRx. She earned her Doctor of Pharmacy degree from the University of Kentucky and is licensed in New York and Massachusetts.

Reviewed by:

Joshua Murdock, PharmD, BCBBS

Joshua Murdock, PharmD, BCBBS, is a licensed pharmacist in Arizona, Colorado, and Rhode Island. He has worked in the pharmacy industry for more than 10 years and currently serves as a pharmacy editor for GoodRx.

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