Flonase - Clinical Pharmacology

Drug Interactions

Fluticasone propionate is a substrate of cytochrome P450 3A4. Coadministration of fluticasone propionate and the highly potent cytochrome P450 3A4 inhibitor ritonavir is not recommended based upon a multiple-dose, crossover drug interaction study in 18 healthy subjects.

Fluticasone propionate aqueous nasal spray (200 mcg once daily) was coadministered for 7 days with three P450 3A4 inhibitors: ritonavir (100 mg twice daily), ketoconazole (200 mg once daily), and erythromycin (500 mg twice daily). Coadministration with ritonavir resulted in a significant increase in plasma fluticasone propionate exposure and a significant decrease (86%) in plasma cortisol area under the plasma concentration versus time curve (AUC).

Coadministration with ketoconazole resulted in a slight increase in fluticasone propionate exposure and a 7% reduction in the area under the plasma cortisol AUC. Coadministration with erythromycin did not affect fluticasone propionate pharmacokinetics; there was a 2% reduction in the plasma cortisol AUC. Caution should be exercised when potent cytochrome P450 3A4 inhibitors (e. g., ketoconazole) are coadministered with fluticasone propionate

Pharmacodynamics

In a trial to evaluate the potential systemic and topical effects of FLONASE Nasal Spray on allergic rhinitis symptoms, the benefits of comparable drug blood levels produced by FLONASE Nasal Spray and oral fluticasone propionate were compared. The doses used were 200 mcg of FLONASE Nasal Spray, the nasal spray vehicle (plus oral placebo), and 5 and 10 mg of oral fluticasone propionate (plus nasal spray vehicle) per day for 14 days. Plasma levels were undetectable in the majority of patients after intranasal dosing, but present at low levels in the majority after oral dosing. FLONASE Nasal Spray was significantly more effective in reducing symptoms of allergic rhinitis than either the oral fluticasone propionate or the nasal vehicle. This trial demonstrated that the therapeutic effect of FLONASE Nasal Spray can be attributed to the topical effects of fluticasone propionate.