Prolia (denosumab) and Fosamax (alendronate) are brand-name drugs. They’re both prescribed for osteoporosis in certain adults. A healthcare professional administers Prolia, while Fosamax can be taken at home.
This article explains the main similarities and differences between Prolia and Fosamax. If you’re considering taking one of these drugs, discussing this information with your doctor can help you determine whether one of the treatments may be right for you.
Note: For more comprehensive information about these two drugs, you can refer to our Prolia and Fosamax articles.
Key differences between Prolia and Fosamax
These are a few of the main differences between Prolia and Fosamax:
- How it’s given: Prolia is given as a subcutaneous injection. Fosamax is taken by mouth. (See the “Dosages, forms, and administration” section below.)
- Dosage: Fosamax is taken more often than Prolia. Fosamax is taken once per day or once per week, while Prolia is given once every 6 months. (See the “Dosages, forms, and administration” section below.)
- Conditions treated: Prolia and Fosamax are both prescribed to treat osteoporosis. Doctors also prescribe Prolia to reduce bone loss in people receiving certain cancer treatments. And Fosamax is used to treat Paget’s disease of bone and help prevent osteoporosis in certain people. (See the “Uses of Prolia vs. Fosamax” section below.)
Below are answers to some common questions about Prolia and Fosamax.
Is Prolia a better treatment option than Fosamax, or vice versa?
It depends on the condition you’re taking the drug to treat and whether you’ve received similar treatments in the past. It may also depend on your preferences.
For instance, you may find Fosamax more convenient because you can take it by mouth at home. However, you may prefer Prolia injections because you’ll only need to receive a dose every 6 months. Typically, you’ll receive Prolia from a healthcare professional at a doctor’s office or clinic.
Talk with your doctor to discuss which of these treatment options may be right for you.
How does Prolia or Fosamax compare with Boniva or Reclast?
Boniva*, Fosamax, Prolia, and Reclast are similar drugs in that doctors prescribe them to treat similar conditions. These conditions include osteoporosis and other conditions that affect your bones.
Boniva, Fosamax, and Reclast belong to the same drug class called bisphosphonates. (A drug class is a group of medications that work in a similar way.) Boniva and Fosamax are taken by mouth, while you’ll receive Reclast as an intravenous (IV) infusion. (With an IV infusion, the drug is slowly injected directly into your vein.) Boniva also comes in a generic form given as an IV infusion.
Prolia belongs to a different drug class called receptor activator of nuclear factor kappa-B ligand (RANKL) inhibitors. It’s given as a subcutaneous injection (an injection under your skin).
If you have specific questions regarding the similarities and differences of these drugs, talk with your doctor or pharmacist.
* Boniva was a brand-name drug that’s no longer available. Its generic form, ibandronate, is still available. Talk with your doctor or pharmacist for more information.
Here’s information about the generic and biosimilar* status for Prolia and Fosamax, as well as details on their active ingredients.
| Prolia | Fosamax | |
| Generic available | no | yes |
| Biosimilar available | no | no |
| Active ingredient | denosumab | alendronate |
| Drug class | receptor activator of nuclear factor kappa-B ligand (RANKL) inhibitor | bisphosphonate |
* Prolia is a biologic drug. Biologics are made using parts of living cells. Because of how they’re made, biologic drugs cannot be copied exactly. So biologic drugs do not have generic versions. Instead, they have biosimilar versions. At this time, there are no biosimilar versions of Prolia available. Fosamax, on the other hand, is not a biologic drug. It’s made using chemicals. A generic version of Fosamax is available.
Keep reading to learn about the effectiveness of Prolia and Fosamax.
Comparison study. Here’s a brief look at whether Prolia or Fosamax was found more effective for treating certain conditions.
Prolia and Fosamax are prescribed to treat osteoporosis in certain people. With osteoporosis, your bones become thin and weak. One way to compare the effectiveness of an osteoporosis treatment is to look at whether the treatment reduces the risk of fracture (broken bone).
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Another way to compare osteoporosis treatments is to look at bone mineral density (BMD). BMD is a measurement of bone strength.
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Note that the results of research studies may not apply to your health situation. Your doctor can help determine whether Prolia or Fosamax may be right for you.
Prescribing information. For details about how these drugs performed in separate clinical trials, see the prescribing information for Prolia and Fosamax. Keep in mind that trial results may not apply to your health situation.
Treatment guidelines. Another way to determine whether a drug is considered effective is to look at treatment guidelines. When an organization includes certain drugs in its treatment guidelines, this means that research has shown the drugs to be safe and effective.
Denosumab (the active drug in Prolia) and alendronate (the active drug in Fosamax) are recommended as treatment options for osteoporosis in guidelines from the American College of Physicians.
Both Prolia and Fosamax are prescribed to treat osteoporosis. These drugs can cause some of the same side effects, as well as some different ones. Some of the side effects reported in clinical trials of these drugs are mentioned below.
For more details about side effects of the two drugs, see our side effect articles about Prolia and Fosamax. You can also refer to the Prolia prescribing information and Fosamax prescribing information.
Mild side effects
The following table lists some of the more commonly reported mild side effects of Prolia and Fosamax. The table may also include mild side effects that are less common but that you might have concerns about in some cases.
| Mild side effects | Prolia | Fosamax |
| back pain | ✓ | |
| pain in your extremities (arms, legs, hands, or feet) | ✓ | |
| musculoskeletal pain (pain in your muscles and bones) | ✓ | ✓ |
| high cholesterol | ✓ | |
| joint pain | ✓ | |
| nasopharyngitis (inflammation in your nose and throat) | ✓ | |
| high blood pressure | ✓ | |
| cystitis (inflammation of the bladder) | ✓ | |
| bronchitis (inflammation of your airway) | ✓ | |
| headache | ✓ | ✓ |
| abdominal pain | ✓ | ✓ |
| acid reflux | ✓ | ✓ |
| constipation | ✓ | ✓ |
| diarrhea | ✓ | |
| indigestion | ✓ | ✓ |
| nausea | ✓ | |
| mild allergic reaction* |
These side effects may be temporary, lasting a few days to weeks. If the side effects last longer than that, bother you, or become severe, be sure to talk with your doctor or pharmacist.
* An allergic reaction is possible after using Prolia and Fosamax, but this side effect wasn’t reported in clinical trials.
Serious side effects
The following table lists the reported serious side effects of Prolia and Fosamax.
| Serious side effects | Prolia | Fosamax |
| decreased level of calcium in your blood | ✓ | ✓ |
| osteonecrosis of the jaw (breaking down of your jawbone) | ✓ | ✓ |
| severe musculoskeletal pain (pain in your muscles and bones) | ✓ | ✓ |
| femur (thigh bone) fracture | ✓ | ✓ |
| slowed production of new bone tissue | ✓ | |
| risk of serious infection | ✓ | |
| severe skin reactions | ✓ | |
| irritation of your upper digestive tract | ✓ | |
| severe allergic reaction* |
If you have serious side effects during Prolia or Fosamax treatment, call your doctor immediately. If the side effects feel life threatening or you believe you’re having a medical emergency, call 911 or your local emergency number right away.
* An allergic reaction is possible after using Prolia and Fosamax, but this side effect wasn’t reported in clinical trials.
Prolia and Fosamax have been approved by the Food and Drug Administration (FDA) to treat the following conditions in adults.
Both Prolia and Fosamax are FDA-approved to treat:
- osteoporosis (a condition that causes thinning and weakening of your bones) in females* after menopause. For Prolia, this treatment is specifically for females who’ve gone through menopause, are at high risk for fracture (broken bone), and cannot take other osteoporosis medications (or have tried other osteoporosis medications, but they didn’t help enough).
- osteoporosis in males.* For Prolia, the drug is specifically approved to increase bone mass in males with osteoporosis who are at high risk for fracture and cannot use other osteoporosis medications.
- osteoporosis due to use of steroids (also called glucocorticoids) in adults. For Prolia, this use is specific to people who will use steroids for at least 6 months and are at high risk for fracture.
Prolia is also FDA-approved to treat:
- bone loss in males who are at high risk for fracture and receiving certain treatments for nonmetastatic** prostate cancer
- bone loss in females who are at high risk for fracture and receiving certain treatments for nonmetastatic breast cancer
Fosamax is also FDA-approved to:
- prevent osteoporosis in females who’ve gone through menopause
- treat Paget’s disease of bone (a condition that causes soft, weak bones) in certain adults
* Sex and gender exist on spectrums. Use of the terms “female” and “male” in this article refers to sex assigned at birth.
** “Nonmetastatic” means the cancer hasn’t spread to other parts of the body.
Your doctor may recommend taking calcium and vitamin D supplements during your treatment with either Prolia or Fosamax. They’ll also advise you on the details of taking these supplements, such as the type and dosage.
Fosamax comes with a limitation of use. The ideal length of time that a person should take Fosamax treatment isn’t known for sure. Because of this, your doctor will periodically check to determine whether you need to continue the drug. If your doctor determines you’re at low risk for fracture, they may have you stop taking Fosamax after 3–5 years of treatment.
Here’s a quick look at the dosage and administration of Prolia and Fosamax for the conditions both drugs treat.
Note: Sex and gender exist on spectrums. Use of the terms “female” and “male” in this article refers to sex assigned at birth.
Dosage for treating osteoporosis in females after menopause
Here’s an overview of the dosage and administration for Prolia and Fosamax for treating osteoporosis in females after menopause. Strengths below are measured in milligrams (mg) and milliliters (mL).
| Prolia for osteoporosis in females after menopause | Fosamax for osteoporosis in females after menopause | |
| Forms | liquid solution, given as a subcutaneous injection using a prefilled syringe | oral tablet and oral solution* |
| Strengths | 60 mg in 1 mL of solution | oral tablet:* • 5 mg • 10 mg • 35 mg • 40 mg • 70 mg oral solution:* • 70 mg per 75 mL of solution |
| Dosing frequency | 60 mg given once every 6 months | 10 mg taken once per day or 70 mg taken once per week |
| Given by | healthcare professional (see below) | self (see below) |
* Fosamax is a brand-name drug. Currently, Fosamax is only available as a 70-mg oral tablet. The generic version of the drug, alendronate, comes in two forms: an oral tablet and an oral solution. Alendronate oral tablets are available in several strengths: 5 mg, 10 mg, 35 mg, 40 mg, and 70 mg. Alendronate oral solution comes in one strength of 70 mg per 75 mL. Your doctor or pharmacist can provide further details about the available forms and strengths of this drug.
Prolia is given as a subcutaneous injection (an injection under your skin). The drug may be injected into your abdomen, upper thigh, or upper arm. Typically, Prolia injections are given by a healthcare professional at a doctor’s office or clinic.
Fosamax (alendronate) is taken by mouth following a specific routine. You’ll take your dose on an empty stomach, typically first thing in the morning, with a glass of plain water. For at least 30 minutes after you take your dose:
- you should sit or stand upright (do not lie down)
- do not eat or drink anything besides plain water
- do not take any other medications or supplements
After 30 minutes, you should stay upright (avoid lying down) until you’ve had something to eat. Following this specific routine helps to prevent certain side effects of alendronate or Fosamax.
Dosage for osteoporosis in males
Here’s an overview of the dosage and administration for Prolia and Fosamax for treating osteoporosis in males.
| Prolia for osteoporosis in males | Fosamax for osteoporosis in males | |
| Forms | liquid solution, given as a subcutaneous injection using a prefilled syringe | oral tablet and oral solution* |
| Strengths | 60 mg in 1 mL of solution | oral tablet:* • 5 mg • 10 mg • 35 mg • 40 mg • 70 mg oral solution:* • 70 mg per 75 mL of solution |
| Dosing frequency | 60 mg given once every 6 months | 10 mg taken once per day or 70 mg taken once per week |
| Given by | healthcare professional (see below) | self (see below) |
* Fosamax is a brand-name drug. Currently, Fosamax is only available as a 70-mg oral tablet. The generic version of the drug, alendronate, comes in two forms: an oral tablet and an oral solution. Alendronate oral tablets are available in several strengths: 5 mg, 10 mg, 35 mg, 40 mg, and 70 mg. Alendronate oral solution comes in one strength of 70 mg per 75 mL. Your doctor or pharmacist can provide further details about the available forms and strengths of this drug.
Prolia is given as a subcutaneous injection (an injection under your skin). The drug may be injected into your abdomen, upper thigh, or upper arm. Typically, you’ll receive Prolia injections from a healthcare professional at a doctor’s office or clinic.
Fosamax (alendronate) is taken by mouth following a specific routine. You’ll take your dose on an empty stomach, typically first thing in the morning, with a glass of plain water. For at least 30 minutes after you take your dose:
- you should sit or stand upright (do not lie down)
- do not eat or drink anything besides plain water
- do not take any other medications or supplements
After 30 minutes, you should stay upright (avoid lying down) until you’ve had something to eat. Following this specific routine helps prevent certain side effects of alendronate or Fosamax.
Dosage for osteoporosis due to steroid use
Here’s an overview of the dosage and administration for Prolia and Fosamax for treating osteoporosis caused by steroid treatment.
| Prolia for osteoporosis due to steroid use | Fosamax for osteoporosis due to steroid use | |
| Forms | liquid solution, given as a subcutaneous injection using a prefilled syringe | oral tablet and oral solution* |
| Strengths | 60 mg in 1 mL of solution | oral tablet:* • 5 mg • 10 mg • 35 mg • 40 mg • 70 mg oral solution:* • 70 mg per 75 mL of solution |
| Dosing frequency | 60 mg given once every 6 months | 5 mg or 10 mg taken once per day |
| Given by | healthcare professional (see below) | self (see below) |
* Fosamax is a brand-name drug. Currently, Fosamax is only available as a 70-mg oral tablet. The generic version of the drug, alendronate, comes in two forms: an oral tablet and an oral solution. Alendronate oral tablets are available in several strengths: 5 mg, 10 mg, 35 mg, 40 mg, and 70 mg. Alendronate oral solution comes in one strength of 70 mg per 75 mL. Your doctor or pharmacist can provide further details about the available forms and strengths of this drug.
Prolia is given as a subcutaneous injection (an injection under your skin). The drug may be injected into your abdomen, upper thigh, or upper arm. Typically, you’ll receive Prolia injections from a healthcare professional at a doctor’s office or clinic.
Fosamax (alendronate) is taken by mouth following a specific routine. You’ll take your dose on an empty stomach, typically first thing in the morning, with a glass of plain water. For at least 30 minutes after you take your dose:
- you should sit or stand upright (do not lie down)
- do not eat or drink anything besides plain water
- do not take any other medications or supplements
After 30 minutes, you should stay upright (avoid lying down) until you’ve had something to eat. Following this specific routine helps prevent certain side effects of alendronate or Fosamax.
How much Prolia or Fosamax costs depends on the treatment plan your doctor prescribes, your insurance plan, and your pharmacy. It’ll also depend on the cost of visiting a healthcare professional to receive doses of Prolia. You can visit Optum Perks* for price estimates of Fosamax.
Both Prolia and Fosamax are brand-name drugs. Prolia is only available as a brand-name drug. Fosamax is available as a generic drug called alendronate. Brand-name medications are often more expensive than generics. Talk with your doctor or pharmacist to learn about Prolia, Fosamax, or alendronate.
* Optum Perks is a sister site of Medical News Today.
Prolia and Fosamax may not be right for you if you have certain medical conditions or other factors that affect your health. The drugs share some of the same precautions, but they also have different ones. Some of these precautions are mentioned below.
If any of the following medical conditions or other health factors are relevant to you, talk with your doctor before using Prolia or Fosamax.
| Precaution | Prolia | Fosamax |
| if you’ve had an allergic reaction to either drug or any of its ingredients | ✓ | ✓ |
| if you’re pregnant or can become pregnant | ✓ | ✓ |
| if you’re breastfeeding or thinking about breastfeeding | ✓ | ✓ |
| if you have chronic kidney disease or are on dialysis | ✓ | ✓ |
| if you have hypocalcemia (low level of calcium in your blood) | ✓ | ✓ |
| if you need teeth removed or dental surgery | ✓ | ✓ |
| if you have immune system problems | ✓ | |
| if you have malabsorption (trouble absorbing minerals) | ✓ | ✓ |
| if you’ve had thyroid or parathyroid surgery | ✓ | |
| if you’re already receiving a drug that contains denosumab (Xgeva) | ✓ | |
| if you have trouble swallowing | ✓ | |
| if you have a condition that affects your digestion or digestive tract | ✓ | |
| if you’re unable to stand or sit upright for at least 30 minutes | ✓ |
Switching between Prolia and Fosamax is possible.
If you’d like to know more about switching between Prolia and Fosamax, talk with your doctor. They can give you additional details and help determine the best treatment approach for your personal situation.
Even if two drugs treat the same condition or are in the same drug class, your body can still respond differently. It’s important that you do not stop, start, or switch any of your drug treatments without your doctor’s recommendation.
Some key points to remember when comparing Prolia and Fosamax include:
- Prolia is given once every 6 months, while Fosamax is taken once per day or once per week.
- Prolia is given as a subcutaneous injection. In contrast, Fosamax is taken by mouth.
- Prolia and Fosamax are both prescribed to treat osteoporosis in certain people. But some of their uses are different. Prolia is used to reduce bone loss in people receiving certain cancer treatments. And Fosamax is used to treat Paget’s disease of bone and to help prevent osteoporosis in certain people.
If you’d like to learn more about Prolia or Fosamax, talk with your doctor or pharmacist. They can help answer any questions you have about similarities and differences between the drugs. They can also help determine whether one drug or the other might work well for you.
Note: For more information about your condition, see our lists of:
Disclaimer: Medical News Today 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.