Final answer:
Toxic substances such as stimulants, depressants, and hallucinogens are metabolized in the liver, which performs the critical function of detoxification through drug metabolism.
Step-by-step explanation:
Toxic substances like stimulants, depressants, and hallucinogens are metabolized mainly in the liver. The liver plays a crucial role in detoxifying these substances through a process known as drug metabolism. The liver has the capability to break down or modify toxic substances such as alcohol, nicotine, and prescription medications, sometimes resulting in toxication when the metabolite is more toxic than its precursor. Ethanol, for example, is broken down into carbon dioxide and water through a series of steps using various liver enzymes. Nicotine is extensively metabolized in the liver to a variety of breakdown products. Moreover, the liver converts toxic ammonia into non-toxic urea, aiding in its excretion from the body.