Background: Two-drug regimens antiretroviral therapies are increasingly prescribed to HIV patients, as they are recommended by international guidelines, and they show an excellent efficacy, safety, and tolerability profile. Regimens administered as single tablets (STRs) are usually preferred by patients and they are associated with higher adherence.
Case report: We report two cases of drug-induced hypersensitivity (DIH) that occurred after switching from dolutegravir (DTG) plus rilpivirine (RPV) in separate pills to a fixed dose combination containing the same molecules (DTG/RPV; Juluca®). Following the DIH event, DTG/RPV coformulation was discontinued. At symptomatic resolution, they continued to receive DTG plus RPV in separate pills uneventfully. The component present only in the DTG/RPV coformulation was iron oxide red (E172), contained in the film-coating. Iron oxide red is an approved colorant, used as drug excipient. Patch test with DTG/RV coformulation performed several months after the DIH event was negative. Drug allergy to excipients remains underappreciated and underreported and frequently leads to inappropriate medication discontinuation.
Conclusion: Our case underscores the role of meticulous medication allergy history in differentiating true medication allergy from excipient allergy. This observation may be useful in the era of antiretroviral simplification to two-drug regimens.
Keywords: DTG/RPV; Drug induced hypersensitivity; excipient; iron oxide red; single tablet regimen.