Is 0.01% steroid that less potent than 1% ? 0.01%含量的激素药膏比1%的更弱效吗？
“There are only two industries that call their customers ‘users’: illegal drugs and software”
— Edward Tufte, a computer scientist, said in The Social Dilemma Netflix 2020 Documentaries.
Less is More
Is 3% topical steroid far more potent than a 0.01%? Short answer, NO.
It is true that 0.25% betamethasone dipropionate is stronger than 0.05% betamethasone dipropionate, however the 0.05% clobetasol propionate is approximately 600-1000 times stronger than 1% hydrocortisone. It is important to remember that the strength of a steroid preparation is not proportional to the % displayed on the label. For example, a 0.01% class I steroid may be hundreds of times more potent compared to a 3% class VII preparation. Understanding how strong the product you received isn’t as easy as reading the label due to the many factors that are at play.
What is steroid potency?
Topical corticosteroids can be subdivided into seven classes in the United States based on their ability to constrict small blood vessels (also known as capillaries) [1,2], with Class One being the most potent and Class Seven the least potent. However, UK and France use four classes. The immunosuppressive effects of topical corticosteroids also acts directly on the DNA level [3-5], the higher the potency of a topical steroid, the higher the risk of getting side effects.
How is the potency determined?
The strength of a topical steroid is determined by a vasoconstrictor test that measures how much it can cause your blood vessels to constrict (blanching of the skin) after topcial applicaiton on healthy skin [6,7]. Investigators assess steroids penetration and their blanching effect with a chromameter to measure the exact skin colour, from absence to strong vasoconstriction. It is evident that the vasoconstriction rankings predicts not only percutaneous absorption but also the risk of side effects. Who can assume that the vasoconstriction on healthy skin is correlated with the anti-inflammatory effect on skin disease?
0.01%含量的药物一定比1%的更弱效吗？至少对于激素药膏来讲，并非如此！ 皮质激素二丙酸倍他米松0.25%的确比0.05%强效，但是0.05%的丙酸氯倍他索皮质激素要比1%的氢化可的松激素强度高出1000倍！看药物标签不能只看数学，更要看文学。
皮质激素强度测量是60年前（1962年）提出，就是在正常皮肤上涂类固醇，然后观察皮肤变得有多么白，医学用语是皮肤真皮上层毛细血管收缩度，用肉眼或者色度计记录皮肤变白的程度，由不变（标记为0）到真的的很白（标记为4），此法简单粗狂沿用至今。至于是否皮肤变白（毛细血管收缩）与皮肤病的治疗有因果关系？我无法确定，可能属于归纳推理吧，但我可以确定激素是个好物件，有哪个用户不想让皮肤变白呢？
“只有两个行业称他们的客户为‘用户’：毒品和软件”
— 计算机科学家爱德华·塔夫特（Edward Tufte）在奈飞2020年纪录片《社会困境》中说。
Reference
- Humbert, P. and Guichard, A. (2015), The topical corticosteroid classification called into question: towards a new approach. Exp Dermatol, 24: 393-395.
- Cornell RC, Stoughton RB. Correlation of the vasoconstriction assay and clinical activity in psoriasis. Arch Dermatol 1985; 121:63.
- Ahluwalia A. Topical glucocorticoids and the skin–mechanisms of action: an update. Mediators Inflamm. 1998;7(3):183-93
- Uva L, Miguel D, Pinheiro C, Antunes J, Cruz D, Ferreira J, Filipe P. Mechanisms of action of topical corticosteroids in psoriasis. Int J Endocrinol. 2012;2012:561018
- Sarah Gabros; Trevor A. Nessel; Patrick M. Zito. Topical Corticosteroids. Treasure Island (FL): StatPearls Publishing; 2022 Jan
- Goa KL. Clinical pharmacology and pharmacokinetic properties of topically applied corticosteroids. A review. Drugs. 1988;36 Suppl 5:51-61.
- Anonymous. Drug Ther Bull 1977: 15: 5–8
