No pharmaceutical opinion available for this interaction.
Calcium (antacid) could bind (chelation) to raltegravir and reduce its absorption .
Possible decrease of clinical efficacy.
Raltégravir 400 mg BID : Interaction clinically non-significant according to the monograph.
Raltegravir 400 mg BID : No dose adjustment or spacing 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.
Viral load HIV
Raltegravir plasma level
|400 mg||1200 mg||1200 mg|
|- 55%||- 72%||- 10%|
|- 52%||- 74%||- 2%|
|- 32%||- 48%||- 57%|
|3000 mg *||3000 mg †||3000 mg ††|
|x 1||x 1||x 1|
Ref #2416 : * Given simultaneously with raltegravir; † Given simultaneously with raltegravir HD; †† Given 12 hours after raltegravir HD.
Furthermore, the product monograph recommends not to give raltegravir 400 mg BID with antacids containing aluminum or magnesium. Antacids with calcium carbonate also reduce raltegravir 400 mg BID Cmin but they consider this decrease clinically non-significant.
See 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.