Stephens Thomas J, Herndon James H, Colón Luz E, Gottschalk Ronald W
Thomas J. Stephens & Associates, Inc., Carrollton, TX, USA.
J Drugs Dermatol. 2011 Feb;10(2):150-5.
To compare the functional stability of Cetaphil UVA/UVB Defense SPF 50 as measured by its ultraviolet B sun protection factor (UVB-SPF) and ultraviolet A protection factor (UVA-PF) values following exposure to natural sunlight versus the UVB-SPF and UVA-PF values of unexposed product.
These two randomized, controlled, evaluator-blinded, single-center trials were conducted according to the methods outlined in the 2007 Proposed Amendment to the Final Monograph, “Sunscreen Drug Products for Over-the-Counter Human Use.” Sunscreen samples were applied to glass plates and exposed to ultraviolet radiation in the form of natural sunlight in four minimal erythemal doses (MED) ranging from 2–6 MED (42–36 mJ/cm2). Three test sites were identified on the back of each study subject. Exposed sunscreen (one of four doses), unexposed sunscreen, and a UVB-SPF 15 control sunscreen were applied to the three test sites in a randomized fashion, followed by UV irradiation of incremental doses. Erythema and pigment darkening responses were assessed immediately following UV exposure and again 16–24 hours (erythema) or three to 24 hours (pigment darkening) after exposure. UVB-SPF and UVA-PF values were calculated for the exposed and unexposed samples.
The calculated UVB-SPF and UVA-PF values for all test samples (exposed and unexposed) were >50 and >9, respectively, which were greater than the stated UVB-SPF and UVA-PF values on the product label. No differences were observed between the exposed and unexposed samples in UVB-SPF or UVA-PF.
The UVA and UVB protection using standard evaluation techniques of Cetaphil UVA/UVB Defense SPF 50 remains stable despite exposure of the sunscreen to natural sunlight containing UVB ranging from 2–16 MED (41–336 mJ/cm2) and coexistent UVA.
通过比较露得清UVA/UVB防护乳SPF 50在自然阳光下照射后的紫外线B防晒系数（UVB-SPF）和紫外线A防护系数（UVA-PF）值与未暴露产品的UVB-SPF和UVA-PF值，来比较其功能稳定性。
这两项随机、对照、评估者盲法、单中心试验是根据2007年《非处方人类用防晒药品最终专论拟议修正案》中概述的方法进行的。将防晒样品涂在玻璃板上，并以自然阳光形式的紫外线辐射进行照射，照射剂量为四个最小红斑剂量（MED），范围为2 - 6 MED（42 - 36 mJ/cm²）。在每个研究对象的背部确定三个测试部位。将暴露的防晒产品（四个剂量之一）、未暴露的防晒产品和一种UVB-SPF 15对照防晒产品以随机方式涂在三个测试部位，然后进行递增剂量的紫外线照射。在紫外线照射后立即以及照射后16 - 24小时（红斑）或3 - 24小时（色素沉着）再次评估红斑和色素沉着反应。计算暴露和未暴露样品的UVB-SPF和UVA-PF值。
所有测试样品（暴露和未暴露）计算出的UVB-SPF和UVA-PF值分别>50和>9, 高于产品标签上标明的UVB-SPF和UVA-PF值。在UVB-SPF或UVA-PF方面，暴露和未暴露样品之间未观察到差异。
尽管露得清UVA/UVB防护乳SPF 50暴露于含有2 - 16 MED（41 - 336 mJ/cm²）UVB和共存UVA的自然阳光下，但使用标准评估技术时其UVA和UVB防护作用仍然稳定。
