Interaction not studied with any of the components of Genvoya. Plasma concentrations of this medicinal product may be increased when co-administered with Genvoya, resulting in reduced serum cortisol concentrations. Concomitant use of Genvoya and corticosteroids that are metabolised by CYP3A (e.g. fluticasone propionate or other inhaled or nasal corticosteroids) may increase the risk of development of systemic corticosteroid effects, including Cushing's syndrome and adrenal suppression. Co-administration with CYP3A-metabolised corticosteroids is not recommended unless the potential benefit to the patient outweighs the risk, in which case patients should be monitored for systemic corticosteroid effects. Alternative corticosteroids which are less dependent on CYP3A metabolism e.g. beclomethasone for intranasal or inhalational use should be considered, particularly for long-term use. For coadministration of cutaneously-administered corticosteroids sensitive to CYP3A inhibition, refer to the prescribing information of the corticosteroid for conditions or uses that augment its systemic absorption.

Coadministration is expected to decrease concentrations of elvitegravir and cobicistat and increase corticosteroid concentrations. Coadministration with oral dexamethasone or other systemic corticosteroids that induce CYP3A may result in loss of therapeutic effect and development of resistance to elvitegravir. Consider alternative corticosteroids. Coadministration with corticosteroids (all routes of administration) whose exposures are significantly increased by strong CYP3A inhibitors can increase the risk for Cushing’s syndrome and adrenal suppression. Alternative corticosteroids including beclomethasone and prednisolone (whose PK and/or PD are less affected by strong CYP3A inhibitors relative to other studied steroids) should be considered, particularly for long-term use.

A case study was reported of a 49-year-old HIV positive woman taking elvitegravir/cobicistat/tenofovir-DF/emtricitabine (Stribild: 150/150/300/200 mg, once daily) who developed severe lower back pain. After NSAID therapy failed to relieve the pain she received two interlaminar epidural injections of 80 mg triamcinolone. One month later she presented with moon facies, mild fatigue and weight gain. Tests revealed she had low ACTH and cortisol and indicated adrenal insufficiency. She continued on Stribild but was not administered further injections of triamcinolone. Follow up visits described eventual resolution of her moon facies and fatigue. The authors hypothesise a drug-drug interaction occurred via inhibition of CYP3A4 by cobicistat, leading to increased triamcinolone exposure and secondary adrenal insufficiency.