Dinitrophenol makes the inner mitochondrial membrane leaky to protons. Until which year was it used as a weight-loss drug?

1. Dinitrophenol is an uncoupler that makes the inner mitochondrial membrane leaky to protons. 2. A leaky membrane lets protons return without passing through the enzyme that makes adenosine triphosphate. 3. It was used until 1938 as a weight-loss drug. 4. No other date is attached to this compound. 5. The decade is easy to slip by ten years in either direction, which is what the other options test. 6. Fixing the year to 1938 is the only claim supported here, so a nearby year cannot be substituted. _Source: OpenStax Biology (1st ed., CC BY 4.0), Ch 7 "Cellular Respiration", section 7.4 Oxidative Phosphorylation_