Short‐term dose‐response relationships for the relative systemic effects of oral prednisolone and inhaled fluticasone in asthmatic adults

Abstract

To determine the systemic dose-response relationships with oral prednisolone and inhaled fluticasone propionate administered in a putative 11:1 mg equivalent basis, in terms of effects on adrenal, bone and haematological markers. Twelve asthmatic patients mean (s.e.) age, 28.8 [3.3] years, FEV1 94.7 [3.6]% predicted, FEF(25-75) 65.5 [6.1]% predicted were studied in a double-blind, double dummy randomised crossover design comparing placebo, inhaled fluticasone propionate via volumatic spacer given twice a day (ex actuator dose 0.44 mg day-1, 0.88 mg day-1, 1.76 mg day-1 ) and oral prednisolone given once daily (5 mg day-1, 10 mg day-1, 20 mg day-1 ). All treatments were for 4 days at each dose level with a 7-day washout at crossover. Measurements were made at 08.00 h after the last dose of each dose level for plasma cortisol, serum osteocalcin and blood eosinophil count. There were significant dose-related effects for suppression of all three endpoints with both prednisolone and fluticasone propionate. Parallel slope analysis revealed a calculated dose ratio for relative potency of 8. 5:1 mg (95% CI 5.7-11.2) comparing Pred with FP for morning cortisol. The magnitude of suppression with FP was less for osteocalcin and eosinophils than for cortisol. Systemic tissues exhibit different dose-response relationships for the effects of inhaled and oral corticosteroids with suppression of cortisol being greater than osteocalcin or eosinophils. For cortisol suppression we observed an 8.5:1 mg relative potency ratio comparing prednisolone with fluticasone propionate. Patients taking high dose inhaled fluticasone propionate should therefore be screened for evidence of impaired adrenal reserve.