How do Maltofer (iron supplement) and calcium carbonate interact?

Interaction Between Maltofer (Iron Supplement) and Calcium Carbonate

Maltofer (iron(III)-hydroxide polymaltose complex) does not significantly interact with calcium carbonate, making concurrent administration safe without the need for separated dosing. 1

Understanding the Supplements

• Maltofer contains iron in a non-ionic form (iron(III)-hydroxide polymaltose complex or IPC), which has different physicochemical properties compared to simple iron salts like iron sulfate 1
• Calcium carbonate provides 40% elemental calcium content but is more likely to cause gastrointestinal side effects like constipation, bloating, and reflux symptoms compared to other calcium supplements 2

Evidence on Interaction

• Laboratory studies in rats demonstrated that iron uptake from Maltofer was not significantly affected when co-administered with calcium carbonate 1
• Iron-59 retrieval from blood and major storage organs was 64-76% for IPC alone compared with 59-85% following co-administration with calcium carbonate and other medications 1
• This contrasts with traditional iron salts (like ferrous sulfate), where calcium carbonate has been shown to significantly reduce iron absorption 3, 4

Mechanism of Non-Interaction

• Traditional iron salts are ionic and prone to binding with other substances, while Maltofer's non-ionic iron form makes it less susceptible to interactions 1
• The polymaltose complex protects the iron from binding with substances like calcium that would normally inhibit absorption of simple iron salts 1

Clinical Implications

• Unlike with traditional iron supplements, patients taking Maltofer do not need to separate their doses from calcium carbonate 1
• This simplifies medication regimens and may improve adherence, as separation of calcium and iron supplements would otherwise necessitate multiple daily administrations 5

Comparison with Traditional Iron Supplements

• Calcium carbonate has been shown to reduce iron retention by approximately 57% when co-administered with traditional iron supplements 3
• Calcium carbonate depresses iron bioavailability more than calcium sulfate or sodium carbonate when using traditional iron forms 4
• When traditional iron is present in a multivitamin with ascorbic acid, the inhibitory effect of calcium carbonate may be mitigated 6

Recommendations for Clinical Practice

• Patients can take Maltofer and calcium carbonate together without timing separation 1
• For patients with GERD or gastrointestinal sensitivity, consider calcium citrate instead of calcium carbonate, as it causes fewer gastrointestinal side effects 2
• If using traditional iron supplements (not Maltofer), separate calcium carbonate administration by at least 2 hours 3

Common Pitfalls to Avoid

• Do not assume all iron supplements behave like Maltofer - traditional iron salts do interact significantly with calcium carbonate 3, 4
• Avoid recommending calcium carbonate to patients with significant reflux symptoms, as it may exacerbate their condition 2
• Be aware that excessive calcium supplementation (above 2,000-2,500 mg per day) may increase risk of kidney stones and potentially cardiovascular events 2