Bithionol (Standard) is the standard substance of Bithionol, and it is applicable for quantitative analysis, quality control, and related research in biochemical experiments. Bithionol (Actamer), formerly marketed as an active ingredient in various topical drug products, was shown to be a potent photosensitizer with the potential to cause serious skin disorders. Approvals of the NDA's for bithionol drug products were withdrawn on October 24, 1967.