Depression of consciousness – coma, specifically – is a frequent complaint in the emergency room consultation and is a challenge for health personnel, considering the number of life-threatening conditions that may be associated with this clinical sign. Toxicity in the central nervous system is one of the most common manifestations in the poisoned patient, where signs and symptoms have been found in up to 30%. This percentage is significant in working-age individuals as morbidity resulting from a delay in care and secondary lesions involves a social impact. According to their effect on the central nervous system, xenobiotics can be divided into two groups: stimulants that cause states of agitation, delirium or convulsions, and depressants that cause varying degrees of alteration in the state of consciousness, anywhere from drowsiness to coma. The purpose of this article was to review depressants, focusing on coma induced by intoxication. In addition to reviewing the pathophysiology and the main toxic substances involved, we consider the best approach to this class of patients based on the evidence, in order to favor the reasonable use of resources available, while avoiding complications and reducing health system costs.