Trong lịch sử, corticosteroid mạnh hơn đã được tạo ra bởi flo hóa, do đó, các sản phẩm flo đã trở thành liên quan với nguy cơ cao hơn các sự kiện bất lợi. Nhưng rõ ràng, nó không phải là flo hóa (hoặc halogenation) cho mỗi gia nhập là kết quả tác dụng phụ corticosteroid | 44 Givan et al. treatment became evident. Historically more potent corticosteroids were created by fluorination thus fluorinated products became associated with higher risk of adverse events. But clearly it is not fluorination or halogenation per se that results in corticosteroid side effects. To the extent that a given compound is able to activate the corticosteroid receptor so too will be its capacity to produce unwanted and detrimental side effects irrespective of the potency-enhancing mechanism. It is an incorrect assumption bordering on myth that nonhalogenated corticosteroids are in any way safer than halogenated ones we can expect that corticosteroids of similar potency will have similar side effect profiles. DELIVERY AND PHYSIOLOGIC POTENCY As with systemic corticosteroid therapy topical corticosteroid therapy and efficacy relies upon activation of the cytoplasmic corticosteroid receptor. However unlike systemic corticosteroids which are ingested or injected intramuscularly topical corticosteroids must reach their target cells by first diffusing across the stratum corneum. Therefore it is essential to realize that topical corticosteroid potency is a function of not only the agent s physiologic potency to activate its cellular receptor but also the ability of that agent to first gain access to the intended area. The ability of a given corticosteroid compound to traverse the stratum corneum involves complex physical chemistry. Furthermore the ability of a formulation to deliver a corticosteroid cannot be predicted and must be assessed or measured clinically. A key concept of the potency of a formulation is the ability of the active agent to separate from the vehicle and diffuse across the stratum corneum. We can envision this as a two-phase system one in which the vehicle sits on the stratum corneum much as olive oil sits on water in Italian dressing . How much drug reaches the targeted skin is determined in large part by how the drug partitions between the .
