How can ritonavir affect exposure to the active ingredients in Relvar Ellipta?

Ritonavir, a strong CYP3A4 inhibitor, can increase systemic exposure to both fluticasone furoate and vilanterol in Relvar Ellipta; co-administration should be avoided unless benefits outweigh the increased risk of systemic corticosteroid adverse effects, in which case patients should be monitored for these effects.