If you have certain kinds of bone problems, your doctor might suggest Fosamax as a treatment option. It’s a prescription drug used for the following reasons in adults:
- to increase bone mass in males* with osteoporosis (thinning of the bones)
- to treat and prevent osteoporosis in postmenopausal females*
- to treat osteoporosis due to corticosteroid drugs
- to treat Paget’s disease of the bone (a chronic bone disorder)
Fosamax comes as a tablet that you swallow. (It’s no longer available in liquid form.) The active ingredient in Fosamax is alendronate sodium. (The active ingredient is what makes a drug work.)
For more information about Fosamax, including details about its uses, see this in-depth article.
Like other drugs, Fosamax can cause mild to serious side effects (also known as adverse effects). Keep reading to learn more.
* In this article, we use the terms “male” and “female” to refer to someone’s sex assigned at birth. For information about the difference between sex and gender, see this article.
Some people may experience mild to serious side effects during their Fosamax treatment. Examples of the drug’s commonly reported side effects include:
- belly pain
- constipation or diarrhea
- nausea
- muscle, joint, or bone pain*
- acid reflux and indigestion*
* To learn more about this side effect, see the “Side effects explained” section below.
Mild side effects have been reported with Fosamax. These include:
- belly pain
- bloating
- changes in your sense of taste
- constipation
- diarrhea
- gas
- headache
- nausea
- vomiting
- mild allergic reaction*
- muscle pain* or cramps
- acid reflux and indigestion*
* To learn more about this side effect, see the “Side effects explained” section below.
In most cases, these side effects should be temporary. And some may be easily managed. But if you have symptoms that are ongoing or bother you, talk with your doctor or pharmacist. And do not stop taking Fosamax unless your doctor recommends it.
Fosamax may cause mild side effects other than those listed above. See the drug’s prescribing information for details.
Serious side effects have been reported with Fosamax. These include:
- low blood calcium levels
- esophagus problems*
- jaw osteonecrosis (death of the bone tissue in the jaw)*
- severe muscle, joint, or bone pain*
- thigh bone fractures*
- severe allergic reaction*†
If you develop serious side effects while taking Fosamax, call your doctor right away. If the side effects seem life threatening or you think you’re having a medical emergency, immediately call 911 or your local emergency number.
* To learn more about this side effect, see the “Side effects explained” section below.
† An allergic reaction is possible after taking Fosamax. But it’s not clear whether this side effect occurred in studies.
Note: After the Food and Drug Administration (FDA) approves a drug, it tracks side effects of the medication. If you’d like to notify the FDA about a side effect you’ve had with Fosamax, visit MedWatch.
Get answers to some frequently asked questions about side effects of Fosamax.
Does Fosamax cause certain side effects in older adults?
The safety and effectiveness of Fosamax in adults ages 65 years and above was similar to younger adults in the drug’s studies. This means the same kinds of side effects are expected in older adults. But it’s possible that older adults may be more sensitive to Fosamax. As a result, they could have a higher risk of developing side effects.
If you have questions or concerns about taking Fosamax at your age, talk with your doctor.
Is weight gain or hair loss a possible side effect of Fosamax?
Neither weight gain nor hair loss was reported in Fosamax studies. There have been reports of people experiencing hair loss, but this was after the drug came on the market. So it’s possible that hair loss may occur from taking Fosamax.
There haven’t been reports of people gaining weight since the drug came on the market. But there have been reports of peripheral edema, which is swelling in the arms or legs. This can cause an increase in weight, but it’s weight from retaining extra fluid, not from added fat.
It’s not known how often hair loss or peripheral edema can occur in people taking Fosamax. It’s also not clear if Fosamax was the cause. If you notice changes in your hair or weight while taking Fosamax, talk with your doctor. They can help you find the cause and manage it.
Will I experience teeth-related side effects with Fosamax?
It’s possible that Fosamax can cause dental side effects. The drug can cause a serious side effect called osteonecrosis of the jaw. Osteonecrosis means the bone tissue dies. In this case, it affects the jawbone. Symptoms can include loosening teeth and other dental problems. To read more about this side effect and the risks of developing it, see the “Side effects explained” section below.
Tell your doctor right away about any changes to your teeth or gums.
How do the side effects of Fosamax compare with the generic alendronate?
Alendronate sodium is the active ingredient in Fosamax. Generic alendronate is an exact copy of the active drug in Fosamax. (A generic is considered just as safe and effective as the original brand-name drug, but it usually costs less.)
Fosamax is only available in a 70-milligram (mg) oral tablet. Generic alendronate is available in the following strengths:
- 5 mg
- 10 mg
- 35 mg
- 40 mg
- 70 mg
There’s also a liquid solution form of generic alendronate that you swallow.
If you have questions about taking generic alendronate, talk with your doctor or pharmacist.
Can Fosamax cause long-term side effects?
Most side effects of Fosamax are mild and last only a few days to weeks. But sometimes side effects may last longer. It’s also possible to develop certain side effects after taking Fosamax for a long time. This includes jaw osteonecrosis (death of the bone tissue in the jaw) and severe muscle, joint, or bone pain.
To read more about these side effects, see the “Side effects explained” section below. And talk with your doctor or pharmacist if you have concerns about long-term use of Fosamax.
Learn more about some of the side effects Fosamax may cause.
Esophagus problems
Fosamax can irritate the upper part of the digestive system, including the esophagus and stomach. In some cases, this can lead to ulcers in the esophagus. Erosion (wearing away of the lining) and perforation (rupture of the wall) of the esophagus can occur. While these conditions are rare, they can be severe and require hospitalization.
Symptoms of esophagus problems can include:
- new or worsening heartburn
- pain behind the breastbone
- pain with swallowing
- trouble swallowing
What might help
Take Fosamax on an empty stomach with a full (6- to 8-ounce) glass of water only. You should be in a sitting or standing position when you take it. Do not lie down or recline for at least 30 minutes after taking your dose.
Tell your doctor right away if you develop any of the symptoms of esophagus problems listed above.
Muscle, joint, or bone pain
Muscle, joint, and bone pain are common side effects of Fosamax. In some cases, this pain can be severe and prevent you from being able to function as usual. This kind of pain can start anywhere from 1 day to several months after starting the drug. Postmenopausal females*may be most likely to get this kind of pain.
* In this article, we use the term ”female” to refer to someone’s sex assigned at birth. For information about the difference between sex and gender, see this article.
What might help
Muscle, joint, or bone pain can be a symptom of other serious side effects. So it’s important to tell your doctor if you experience any of these kinds of pain. For severe pain, your doctor may recommend stopping Fosamax and trying a different treatment. They may also need to check for fractures or other bone problems.
Osteonecrosis of the jawbone
Osteonecrosis of the jawbone is death of the bone tissue in the jaw. Symptoms can include:
- exposed bone in the mouth
- loosening teeth
- numbness in the mouth or jaw
- pain, redness, or swelling in the mouth or jaw
- pus or other signs of infection in the gums
The risk of developing osteonecrosis of the jaw may be higher in people who:
- have limited routine mouth care
- have a tooth extraction or other invasive dental procedure while taking Fosamax
- have cancer or are undergoing cancer treatments, such as chemotherapy
- have other oral care issues, such as pre-existing dental disease or ill-fitting dentures
- have other certain medical conditions, such as anemia, clotting disorders, or infection
- take Fosamax for a long time
What might help
Your doctor may recommend visiting the dentist before starting Fosamax. During Fosamax treatment, it’s important to practice good mouth care and see your dentist regularly. You’ll also need to tell your doctor about any planned dental procedures. They may recommend that you stop Fosamax beforehand.
If you notice any changes in your mouth, jaw, or teeth, contact your doctor right away.
Acid reflux and indigestion
Acid reflux and indigestion are common side effects of Fosamax. In most cases they’re mild, but they can be symptoms of something more serious, including esophagus problems.
What might help
To prevent irritation of the stomach and esophagus, take Fosamax on an empty stomach with a full (6- to 8-ounce) glass of water only. You should be in a sitting or standing position when you take it. Do not lie down or recline for at least 30 minutes after taking your dose.
Tell your doctor about any new or worsening digestive tract symptoms, including indigestion and heartburn.
Thigh bone fractures
Thigh bone fractures that aren’t a result of trauma can occur in people taking Fosamax. But it’s not clear if Fosamax is the cause. That’s because this kind of fracture can happen to people who have osteoporosis and don’t take Fosamax.
Symptoms can include:
- dull, achy thigh pain
- groin or hip pain
What might help
Tell your doctor about any new or unusual pain in your hip, groin, or thigh.
Allergic reaction
Like most drugs, Fosamax can cause an allergic reaction in some people. But it’s not clear whether this side effect occurred in studies. Symptoms can be mild to serious and can include:
- skin rash
- itchiness
- flushing (temporary warmth, redness, or deepening of skin color)
- swelling under your skin, usually in your eyelids, lips, hands, or feet
- swelling of your mouth, tongue, or throat, which can make it hard to breathe
What might help
If you have mild symptoms of an allergic reaction, such as a mild rash, call your doctor right away. They may suggest a treatment to manage your symptoms. Examples include:
- an antihistamine you swallow, such as Benadryl (diphenhydramine)
- a product you apply to your skin, such as hydrocortisone cream
If your doctor confirms you’ve had a mild allergic reaction to Fosamax, they’ll decide if you should continue taking it.
If you have symptoms of a severe allergic reaction, such as swelling or trouble breathing, call 911 or your local emergency number right away. These symptoms could be life threatening and require immediate medical care.
If your doctor confirms you’ve had a serious allergic reaction to Fosamax, they may have you switch to a different treatment.
Keeping track of side effectsDuring your Fosamax treatment, consider taking notes on any side effects you’re having. You can then share this information with your doctor. This is especially helpful when you first start taking new drugs or using a combination of treatments.
Your side effect notes can include things such as:
- what dose of the drug you were taking when you had the side effect
- how soon you had the side effect after starting that dose
- what your symptoms were
- how it affected your daily activities
- what other medications you were taking
- any other information you feel is important
Keeping notes and sharing them with your doctor will help them learn more about how Fosamax affects you. They can then use this information to adjust your treatment plan if needed.
Fosamax may not be right for you if you have certain medical conditions. (This is known as a drug-condition interaction.) Other factors may also affect whether this drug is a good treatment option for you. Talk with your doctor about your health history before starting Fosamax. Factors to consider include those described below.
Allergic reaction. If you’ve had an allergic reaction to Fosamax or any of its ingredients, your doctor will likely not prescribe it for you. Ask them about other medications that might be better options.
Dental surgery. Having dental surgery, including a tooth extraction, increases the risk of jaw osteonecrosis (death of the bone tissue in the jaw). To read more about this side effect and the risks of developing it, see the “Side effects explained” section above.
Tell your doctor about any planned dental procedures and ask if you should stop taking Fosamax beforehand.
Kidney problems. Fosamax is not recommended for people with severe kidney problems. This is because your kidneys filter the drug. When they’re not working properly, the amount of drug in your system increases. And this raises your risk of side effects. People with kidney problems should talk with their doctor to find out if Fosamax is the right choice for them.
Low blood levels of calcium. People with low blood levels of calcium should not take Fosamax because it can make the problem worse. Your doctor may check your blood calcium levels before you start this drug. If your calcium level is low, they’ll treat that before you start Fosamax. They may also recommend that you take calcium and vitamin D throughout your Fosamax treatment and check your calcium levels often.
If you know you have low calcium levels, talk with your doctor and ask about your options.
Swallowing problems. Fosamax isn’t recommended for people who have trouble swallowing. It increases the risk of serious esophagus problems. To read more about this side effect, see the “Side effects explained” section above.
Tell your doctor before starting Fosamax if you have problems swallowing. Ask them about other medications that might be better choices for you.
Trouble standing or sitting for at least 30 minutes. People who can’t remain sitting or standing for at least 30 minutes after swallowing Fosamax should not take the drug. This increases the risk of serious esophagus problems. To read more about this, see the “Side effects explained” section above.
Before starting Fosamax, tell your doctor if you’re not able to sit or stand for 30 minutes at a time. Ask them about other treatment options that might be better for you.
Upper digestive system problems. People with esophagus problems should not take Fosamax. And it isn’t recommended for people who have other upper digestive system problems, such as gastritis or ulcers. Taking Fosamax with these conditions increases the risk of the disease worsening. It also increases your risk of developing serious esophageal side effects. To read more about this, see the “Side effects explained” section above.
Tell your doctor about any upper digestive system problems you have before you start Fosamax. They can help you determine if this treatment is right for you.
Alcohol and Fosamax
There are no known interactions between alcohol and Fosamax. But long-term excessive use of alcohol can be bad for your bones. Doctors prescribe Fosamax for bone problems, so drinking alcohol may be counterproductive.
Talk with your doctor to find out if drinking alcohol while taking Fosamax is safe for you. If you drink alcohol, keep in mind that you need to wait at least 30 minutes after taking Fosamax with a full glass of water before having any other beverages or foods.
Pregnancy and breastfeeding while taking Fosamax
It’s not known if Fosamax is safe to take during pregnancy or while breastfeeding. Tell your doctor right away if you become pregnant while taking Fosamax. They’ll likely recommend you stop taking the drug.
Fosamax has some common side effects that are usually mild. But serious side effects are possible. Here are some questions you may want to ask your doctor to help you decide if this drug is right for you:
- Do I have a higher risk of side effects compared with other people who take Fosamax?
- How long do side effects from this drug usually last?
- What can I do to manage or prevent common side effects of Fosamax?
- How do the side effects of this drug compare with other drugs used to treat my condition?
To learn more about Fosamax, see these articles:
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Disclaimer: Healthline has made every effort to make certain that all information is factually correct, comprehensive, and up to date. However, this article should not be used as a substitute for the knowledge and expertise of a licensed healthcare professional. You should always consult your doctor or another healthcare professional before taking any medication. The drug information contained herein is subject to change and is not intended to cover all possible uses, directions, precautions, warnings, drug interactions, allergic reactions, or adverse effects. The absence of warnings or other information for a given drug does not indicate that the drug or drug combination is safe, effective, or appropriate for all patients or all specific uses.