What was the first medication to be sold in water-soluble tablets?

This multi-purpose drug was first stabilized and patented during three years from 1897 to 1900 by Felix Hoffman, a chemist with Friedrich Bayer & Co. in Germany. First, Bayer began distributing aspirin to doctors to give to their patients in a powdered formula. In 1900, Bayer introduced water-soluble tablets, representing the first-ever medication to be sold in this form. In 1915, prescriptions for aspirin became unnecessary. Before long, aspirin was the most popular drug in the world.

Source: Lemelson-MIT