BSP and BDP could be hydrolyzed by phosphatase as fast-release phosphate prodrugs and esterase enzymes as sustained-release dipropionate prodrugs into active pharmaceutical ingredients betamethasone (BOH), betamethasone 17-monodipropionate (B17P) and betamethasone 21-monodipropionate (B21P), respectively. Because the activating enzymes such as phosphate and esterase were highly efficient and ubiquitous in human blood, BSP that was highly ionized and hydrophilic could be rapidly absorbed into blood from the administration place and then be metabolized quickly into active betamethasone (BOH) without a rate-limiting step.
