There are a large number of toxins that can lead to coma of which the most common (in Australia) are

In addition there are a number of less common toxins, which are important to diagnose as they have severe effects and specific treatment.

Clearly, there are also large numbers of other drugs that may lead to impairment of consciousness by reducing cerebral blood flow or causing seizures. These will not be discussed here.

Features that help to differentiate between these drugs are