Weakened or antagonised effect of β
2-adrenergic agonists eg, vilanterol w/ β-adrenergic blockers. Potential for increased systemic exposure to both fluticasone furoate & vilanterol w/ strong CYP3A4 inhibitors (eg, ketoconazole, ritonavir, cobicistat-containing products). May potentiate ARs w/ other long-acting muscarinic antagonists or long-acting β
2-adrenergic agonists. May potentiate possible hypokalaemic effect of β
2-adrenergic agonists w/ methylxanthine derivatives, steroids, or non-K-sparing diuretics.