Calcium and acid inhibitors and QUM

Calcium and acid inhibitors and QUM are a seemingly unusual combination. Some acid inhibitors may reduce the effectiveness of some calcium interventions. What does this have to do with QUM (Quality Use of Medicines)?

Mechanisms and consequences 

The relationships

The therapeutic effectiveness of calcium carbonate when an acid inhibitor is also prescribed, is being questioned. Is calcium carbonate the best option? Why is it the preferred option?

Calcium

Calcium is not absorbed in the stomach it is absorbed in the intestines. The stomach is where calcium is either converted to a soluble form such as Ca2+ or is bound to a soluble organic molecule. This solubilization enables its intestinal absorption.

Release of calcium from its compound may require a source of acid – either gastric or dietary.

Acid inhibitors

Acid inhibitors reduce the amount of acidity released from the gastric parietal cells into the stomach, and include -

H2 antagonists (H2As). Block the histamine receptors. Increase gastric pH to a median of about 2-3. Can maintain intragastric pH > 4 for 4 hours. Short duration of effect.

Proton pump inhibitors (PPIs). Inhibit the proton pumps. Increase gastric pH to about 4-6. Can maintain intragastric pH > 4 for 15-22 hours.

Potassium-competitive acid blockers (P-CABs). Bind to proton pumps in a K⁺-competitive manner. Early evidence indicates they maintain a pH > 4 for longer than PPIs.

Comments about PPIs in this post are deemed relevant to P-CABs because of their many similarities. However, there is currently no specific evidence likely due to their recent formulation.

Quality Use of Medicines (QUM)

QUM’s role is to improve medication safety and quality by reducing prescription errors and harm. Its initiatives include –

 - promotion of appropriate, judicious, safe and effective medication use,

 - reviewing prescription data to facilitate improvement.

Ultimately QUM is about the administration of the correct medicine, at the appropriate time, to the right person.

Calcium and acid inhibitors

A common prescription combination is calcium carbonate and a PPI. A P-CAB and calcium combination is likely to become commonplace as more is known about P-CABs. Duration of these prescription combinations is typically years not months.

PPI prescription means suppression of gastric acidity. Absorption of calcium from calcium carbonate is minimal if administered whilst fasting ie on an empty stomach. Calcium carbonate must therefore be taken at mealtimes.

Calcium from calcium citrate is not dependent on pH for absorption and therefore can be administered at any time.

H2As are considered unlikely to negatively impact calcium status.

Pharmaceutical Benefits Scheme (PBS) influence

The PBS is the vehicle by which the government subsidises the cost of medicine for most medical conditions.

Ultimately which calcium intervention is recommended seems to be based on cost to the consumer.

QUM

The cost versus benefit issue makes this a QUM matter.

Prescribers and consumers are unaware concurrent prescription of a PPI means calcium carbonate interventions are ineffective unless taken with meals.

My spot check of PPI documents found neither their Consumer Medicine Information (CMI) nor their Product Information (PI) include recommendations that -

- calcium carbonate interventions should be administered with meals;

- calcium citrate interventions can be administered at any time.

This omission means -

- the right consumer is being given the right intervention likely at the wrong time; and therefore

- the taxpayer is subsidizing an ineffective intervention.

I suggest 2 strategies to address this significant QUM issue –

- PBS listing for calcium citrate;

- require the CMI and PI documents for PPIs to include appropriate calcium management strategies.

Currently the medicine may be correct but the timing may not be.

Clinical concerns

What actions will you initiate when you see someone prescribed both calcium carbonate and a PPI – will you -

- check that the calcium carbonate intervention is being consumed with meals?

- recommend changing to calcium citrate to ensure adequate calcium absorption?

- contact your pharmaceutical Regulator and request appropriate calcium management strategies be included in the CMI and PI when prescribed a PPI?

Conclusions

Calcium and acid inhibitors are a combination that requires the right medicine to be administered at the right time. But is it?

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The information in this article is provided to support Health Professionals. It is not an exhaustive protocol and Health Professionals are advised that adequate professional supervision is accessed to ensure that Duty of Care obligations with respect to safe administration of medicines is met for each consumer.