No pharmaceutical opinion available for this interaction.
Calcium (supplements) could bind (chelation) to raltegravir and reduce its absorption .
Possible decrease of clinical efficacy.
Raltegravir 400 mg BID : No dose adjustment is necessary.
However, in presence of non-compliance or virological failure: consider a spacing between calcium and raltegravir of at least 3 hours.
Since the time to reach the maximum fasting plasma concentration of the latter is 3 hours.
Monitor for clinical efficacy.
Raltegravir HD 1200 mg QD : Association not recommended.
See the case report and the comments.
Raltegravir plasma level
Viral load HIV
Ref #2416 : Co-administration of an antacid containing calcium carbonate with raltegravir 400 mg BID decreased AUC and Cmin of the latter by 55% and 32%, respectively. This decrease is considered clinically nonsignificant. Product monograph recommends not to give raltegravir 400 mg BID with antacids containing aluminum or magnesium. For more details, see raltegravir + calcium (antacid) and raltegravir + antiacids.
Ref #3083 : A case report describes a 39-year-old HIV-1-infected man who experienced virologic failure while receiving a raltegravir-containing antiretroviral regimen with concomitant calcium administration. For drug interaction reasons, the patient was switched from a PI-based regimen to raltegravir/tenofovir/emtricitabine and calcium carbonate (1 g-vitamin D3 400 IU 3 times/day) was added for prevention of osteoporosis. After 10 months of an undetectable viral load and clinical evidence of a high level of adherence on this regimen, the patient developed detectable HIV-1 RNA levels with documented resistance to raltegravir. His antiretroviral therapy was changed back to a protease inhibitor-based regimen, and his HIV-1 RNA level rapidly resuppressed. Therapeutic drug monitoring at the time of virologic failure showed lower than expected raltegravir concentrations at 5 hour post dose, but tenofovir and emtricitabine concentrations were within the expected range. The authors suggest that calcium binding to the divalent metal ion-chelating motif of raltegravir may have led to subtherapeutic raltegravir levels in this patient.
Ref #3443 : However, in a pharmacokinetic study, coadministration of raltegravir 400mg BID with a multivitamin containing divalent cations (108 mg of calcium, 12 mg of iron and 30 mg of magnesium) in healthy volunteers did not show significant changes in raltegravir PK parameters. For more details, see raltegravir + multivitamins.
Use of calcium supplements with raltegravir HD 1200 mg QD is not recommanded because studies with antacids containing calcium carbonate have shown a more pronounced reduction in raltegravir Cmin when given with raltegravir HD 1200 mg QD compared to raltegravir 400 mg BID. A similar effect with calcium supplements cannot be excluded.