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Etidronate/Calcium Carbonate - Oral

Pronunciation: e-ti-DROE-nate/KAL-see-um KAR-bo-nate

Common Brand Name(s): Didrocal

Important: How To Use This Information

This is a summary and does NOT have all possible information about this product. This information does not assure that this product is safe, effective, or appropriate for you. This information is not individual medical advice and does not substitute for the advice of your health care professional. Always ask your health care professional for complete information about this product and your specific health needs.


This product is used to prevent and treat certain types of bone loss (osteoporosis). It contains 2 medications. Etidronate belongs to a class of medications called bisphosphonates. It works by decreasing the activity of cells that break down bone. Calcium is a mineral that is very important in the body. It is necessary for normal functioning of nerves, cells, muscle, and bone. If there is not enough calcium in the blood, then the body will take calcium from bones, thereby weakening bones. Slowing bone loss and having the right amount of calcium is important for building and keeping strong bones, which in turn helps to reduce the risk of broken bones.

Your risk of developing osteoporosis increases as you grow older, after menopause due to lower levels of natural estrogen hormones, and when you are taking corticosteroid medications (e.g., prednisone) for long periods.

How To Use

Read the Patient Information Leaflet provided by your pharmacist before you start using this product. If you have any questions, consult your doctor or pharmacist.

This product comes as a package with 5 separate blister cards meant to be taken for a 3-month cycle. The first blister card contains a 14-day supply of etidronate. Use this blister card first, taking each dose of etidronate by mouth on an empty stomach (2 hours before or after eating), usually once daily or as directed by your doctor. Take with a full glass of water (8 ounces or 240 milliliters) unless your doctor directs you otherwise. Do not lie down for at least 30 minutes after taking this medication.

Avoid taking etidronate within 2 hours of food or any products containing iron, magnesium, calcium, or aluminum (e.g., antacids, laxatives, certain supplements, milk). Doing so may reduce the amount of drug that is absorbed by your body. Consult your doctor or pharmacist for more details.

The other 4 blister cards contain calcium carbonate. Start taking the calcium after you finish the 14-day supply of etidronate. Take this medication by mouth with food, usually once daily or as directed by your doctor.

Use this medication regularly to get the most benefit from it. To help you remember, take it at the same time each day. Talk to your doctor about the risks and benefits of long-term use of this medication.

If your doctor has recommended that you follow a special diet, it is very important to follow the diet to get the most benefit from this medication and to prevent serious side effects. Your doctor may also direct you to take additional supplements/vitamins (e.g., calcium, vitamin D). Follow your doctor's instructions closely, and do not take any other supplements/vitamins unless ordered by your doctor.

Side Effects

Diarrhea, nausea, headache, upset stomach, or leg cramps may occur with etidronate. Constipation and upset stomach may occur with calcium. If any of these effects persist or worsen, tell your doctor or pharmacist promptly.

To prevent constipation, eat dietary fiber, drink enough water, and exercise. You may also need to take a laxative. Ask your pharmacist which type of laxative is right for you.

Tell your doctor right away if any of these unlikely but serious side effects occur with calcium:

  • vomiting
  • loss of appetite
  • unusual weight loss
  • mental/mood changes (e.g., confusion)
  • bone/muscle pain
  • increased thirst/urination
  • weakness
  • unusual tiredness

Tell your doctor right away if any of these unlikely but serious side effects occur with etidronate:

  • mental/mood changes (e.g., confusion, depression)
  • jaw pain
  • new or increased bone/joint/muscle pain
  • new or unusual hip/thigh/groin pain
  • hair loss
  • easily broken bones
  • muscle weakness
  • skin numbness/tingling
  • easy bruising/bleeding
  • signs of infection (e.g., fever, persistent sore throat)

Etidronate may rarely cause irritation and ulcers in your stomach or esophagus. Seek immediate medical attention if any of these serious side effects occur:

  • new/severe/worsening heartburn
  • chest pain
  • difficult/painful swallowing
  • stomach/abdominal pain
  • black/tarry stools
  • vomit that looks like coffee grounds

A very serious allergic reaction to this drug is rare. However, seek immediate medical attention if you notice any symptoms of a serious allergic reaction, including:

  • rash
  • itching/swelling (especially of the face/tongue/throat)
  • severe dizziness
  • trouble breathing

This is not a complete list of possible side effects. If you notice other effects not listed above, contact your doctor or pharmacist.

In the US -

Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088 or at

In Canada - Call your doctor for medical advice about side effects. You may report side effects to Health Canada at 1-866-234-2345.


Before taking this medication, tell your doctor or pharmacist if you are allergic to etidronate; or to other bisphosphonates (e.g., alendronate); or if you have any other allergies. This product may contain inactive ingredients, which can cause allergic reactions or other problems. Talk to your pharmacist for more details.

This medication should not be used if you have certain medical conditions. Before using this medicine, consult your doctor or pharmacist if you have:

  • a certain bone disorder (osteomalacia)

Before using this medication, tell your doctor or pharmacist your medical history, especially of:

  • diarrhea that doesn't stop
  • decreased or no stomach acid (achlorhydria)
  • kidney disease (e.g., kidney stones)
  • stomach/intestinal ulcers
  • esophagus problems (such as esophageal stricture, achalasia)
  • trouble swallowing
  • colitis
  • heart disease
  • asthma
  • a certain disease that causes swelling (sarcoidosis)
  • difficulty absorbing nutrition from food (malabsorption syndrome)

Some people taking etidronate may have serious jawbone problems. Your doctor should check your mouth before you start this medication. Tell your dentist that you are taking this medication before you have any dental work done. To help prevent jawbone problems, have regular dental exams and learn how to keep your teeth and gums healthy. If you have jaw pain, tell your doctor and dentist right away.

Before having any surgery (especially dental procedures), tell your doctor and dentist about this medication and all other products you use (including prescription drugs, nonprescription drugs, and herbal products). Your doctor or dentist may tell you to stop taking this medication before your surgery. Ask for specific instructions about stopping or starting this medication.

Kidney function declines as you grow older. This medication is removed by the kidneys. Elderly people may be at greater risk for side effects while using this drug.

Caution is advised if you are pregnant or planning to become pregnant in the future. Etidronate may stay in your body for many years. Its effects on an unborn baby are not known. Discuss the risks and benefits with your doctor before starting treatment with etidronate.

It is not known if etidronate passes into breast milk. Consult your doctor before breast-feeding.

Drug Interactions

See also the How to Use section.

Your doctor or pharmacist may already be aware of any possible drug interactions and may be monitoring you for them. Do not start, stop, or change the dosage of any medicine before checking with your doctor or pharmacist first.

Before using this medication, tell your doctor or pharmacist of all prescription and nonprescription/herbal products you may use, especially of:

  • "blood thinners" (e.g., warfarin)
  • certain phosphate binders (e.g., calcium acetate)
  • digoxin
  • aspirin

Calcium can decrease the absorption of other drugs such as tetracycline antibiotics (including doxycycline, minocycline), estramustine, strontium, levothyroxine, and quinolone antibiotics (e.g., ciprofloxacin, levofloxacin). Separate your doses of these medications as far as possible from your doses of calcium. Ask your doctor or pharmacist about how long you should wait between doses and for help finding a dosing schedule that will work with all your medications.

Check the labels on all your prescription and nonprescription/herbal products (e.g., antacids, vitamins) because they may contain calcium. Ask your pharmacist about using those products safely.

This medication may interfere with certain laboratory/medical tests (including bone scans), possibly causing false results. Make sure laboratory personnel and all your doctors know you use this drug.

This document does not contain all possible interactions. Before using this product, tell your doctor or pharmacist of all the products you use. Keep a list of all your medications with you, and share the list with your doctor and pharmacist.


If someone has overdosed and has serious symptoms such as passing out or trouble breathing, call 911. Otherwise, call a poison control center right away. US residents can call their local poison control center at 1-800-222-1222. Alberta residents can call PADIS (Poison and Drug Information Service) 24 hours a day at 1-800-332-1414. Canada residents can call a provincial poison control center. Symptoms of overdose for etidronate may include: vomiting, numbness/tingling of the hands/feet, severe diarrhea, change in the amount of urine, broken bone, easy bruising/bleeding. Symptoms of overdose for calcium may include: nausea/vomiting, loss of appetite, mental/mood changes, weakness, tiredness.


Do not share this medication with others.

Laboratory and/or medical tests (e.g., bone mass, calcium/phosphate levels, kidney function) should be performed periodically to monitor your progress or check for side effects. Consult your doctor for more details.

Lifestyle changes that help promote healthy bones include increasing weight-bearing exercise, stopping smoking, limiting alcohol, and eating well-balanced meals that contain adequate calcium and vitamin D. Since you may also need to take calcium and vitamin D supplements and make lifestyle changes, consult your doctor for specific advice.

Missed Dose

If you miss a dose, take it as soon as you remember. If it is near the time of the next dose, skip the missed dose. Take your next dose at the regular time. Do not double the dose to catch up.

If you have questions about missing a dose or you don't have more medication, contact your healthcare provider or pharmacist.


Store at room temperature between 59-86 degrees F (15-30 degrees C) away from light and moisture. Do not store in the bathroom. Keep all medicines away from children and pets.

Do not flush medications down the toilet or pour them into a drain unless instructed to do so. Properly discard this product when it is expired or no longer needed. Consult your pharmacist or local waste disposal company for more details about how to safely discard your product.

This information does not replace the advice of a doctor. Healthwise, Incorporated, disclaims any warranty or liability for your use of this information. Your use of this information means that you agree to the Terms of Use. Learn how we develop our content.