Vasokin
Vasokin was an experimental drug which increased blood flow to humanoid organs. In 22% of studied cases, it caused severe damage to the lungs, kidneys, heart, and brain.
In 2371, Dr. Julian Bashir administered vasokin to Vedek Bareil Antos in an attempt to save his life. Unfortunately, this led to irreversible brain damage. (DS9: "Life Support")