Green Oncology: Calcium Supplementation and Reducing the Fracture Risk with Aromatase Inhibitors

Guest post by Amy Smith


Green Oncology: Calcium Supplementation and Reducing the Fracture Risk with Aromatase Inhibitors


The Patient Issue:

Many post-menopausal women with breast cancer will be taking aromatase inhibitors (AIs) such as anastrozole, exemestane, or letrozole.  With AI’s having a fracture risk between 6-11% the risk is real.  This is an opportunity for pharmacists to provide some clear advice in preventing fractures for these patients.


The Pharmacist’s Advice:

As pharmacists, we tend to focus on patient’s pharmaceutical therapy and glaze over non-pharmacological measures. Patients can reduce the risk of a fracture by limiting tobacco, alcohol, and caffeine.  In addition, weight-bearing exercises can improve bone health.  Now this doesn’t mean handing out World Gym memberships with each box of anastrozole because yoga, tai chi, golf, and walking are all considered weight bearing.

Calcium supplementation may benefit some patients, but assessing the need for supplementation is an important first step.  With any medication, there are draw backs to consider and calcium is no exception with a recent BMJ meta-analysis showing that there may be an increased risk of myocardial infarction in patients on calcium supplementation.  The benefits are real but they must be balanced with the potential risks. 

A recent change in the osteoporosis guidelines suggest post-menopausal women (patients >50 years) require 1200 mg of elemental calcium per day (down from 1500 mg recommended in the 2002 guidelines).  Vitamin D is recommended at 1000 IU per day however higher doses have been proven to be safe.

Patients can estimate their calcium intake by using the osteoporosis calcium calculator.   (  Personally I rarely drink milk and my diet still contained 840mg of calcium daily.  Just because your patient states “I don’t like milk” doesn’t automatically mean starting calcium carbonate 500 mg TID is appropriate.

When recommending a particular calcium supplement for your patients there are a couple important points to consider which are unique to oncology patients.      


Calcium Type



Specific to Oncology

Calcium carbonate


-Easy to find

-Variety of dosage forms

-Those taking H2 receptor antagonists (e.g. ranitidine) or PPIs (e.g. pantoprazole), or elderly patients, have reduced stomach acid which inhibits absorption

-Many oncology patients are elderly and/or on medications to reduce acid reflux therefore calcium carbonate may not be the best selection

Calcium citrate

-Easily absorbed in the presence of H2 receptor antagonists, PPIs, or reduced stomach acid

-Less elemental calcium per tablet therefore a greater quantity of tablets may be required to achieve the recommended dose

-Less product selection

-Increased cost/tablet

-May be the best for optimal absorption

Calcium with Magnesium

-Calcium may constipate patients and magnesium may cause diarrhea therefore the combination may have a neutral effect on patients’ bowels

-Provides supplementation for those with hypomagnesium

-Magnesium is not required for the absorption of calcium therefore may be an unnecessary medication in those who tolerate calcium

-The addition of an unwarranted medication may further contribute to the polypharmacy experienced by many oncology patients

Administration Note:  The body can absorb only 500 mg of calcium at a time.  Therefore when supplementing be sure to recommend dividing doses through out the day.  


The Bottom Line:

            Many options are available in reducing fracture risk in women using AIs.  In all patients, consider non-pharmacological measures and assess daily calcium intake prior to recommending supplementation.  In oncology patients requiring a calcium supplement, consider all your options, not just calcium carbonate, when making a recommendation.


Thanks for reading!