异维A酸（Isotretinoin），是维A酸的异构体，最初是一种治疗脑癌、胰脏癌和皮肤癌等多种癌病，但现时常用作治疗青春痘，通常为口服用A酸，外用A酸则通常为维A酸成份），有时亦用作医治斑色鱼鳞癣。它属于衍生自维生素A的类视色素，人体可自然形成小量的此化学物。

自2002年2月起，罗氏药厂对异维A酸专利权届满后，市面有多间厂商生产通用名药物。其中中国商品名称叫作「泰尔丝」或「特维丝」，其余常见药名包括Accutane、Amnesteem、Claravis、Decutan、Isotane、Sotret、Oratane、Isotrex和Isotrexin等。

Isotretinoin (INN) (etymology and pronunciation), also known as 13-cis retinoic acid and first marketed as Accutane by Hoffmann-La Roche, is an oral pharmaceutical drug primarily used to treat severe nodular acne. Rarely, it is also used to prevent certain skin cancers (squamous-cell carcinoma), and in the treatment of other cancers. It is used to treat harlequin-type ichthyosis, a usually lethal skin disease, and lamellar ichthyosis. It is a retinoid, meaning it is related to vitamin A, and is found in small quantities naturally in the body. Its isomer, tretinoin, is also an acne drug.