Potency ratio--a brief synopsis.

Deflazacort (DFZ) is a novel glucocorticoid with bone sparing properties, and there have been numerous studies investigating its potency relative to other glucocorticoids. As estimates of potency are difficult to evaluate in patients with disease, the concept of minimum effective dose is used. In double-blind, crossover studies, paired patient studies and between-patient studies, the potency of DFZ to prednisone (PDN) and to methylprednisolone was established as being 1.28:1 (1.17-1.38, 95% CI) and 1.6:1 (1.45-1.75, 95% CI), respectively. The bone wasting properties of DFZ have been determined using the concept of bone wasting ratio (ratio between bone loss velocity values observed in patients given the minimum effective doses of two glucocorticoids). The results of three studies which have evaluated the bone wasting ratio of PDN to DFZ indicate that this ratio is approximately 2.03:1 (1.84-2.23, 95% CI). That is, at therapeutically equivalent doses, twice as much bone loss occurs with PDN as with DFZ.