Individuals with severe mental illness face a substantially higher risk of suicide compared with the general population, with drug overdose representing one of the most common and potentially lethal methods. This narrative review explores toxidromes frequently encountered in psychiatric populations, such as opioid, anticholinergic, and serotonergic toxicity, highlighting the clinical presentation in intentional overdose. Emphasis is placed on clinical recognition, antidote-based treatment, and systems-level strategies for the prevention of lethal overdose. We conducted a comprehensive literature search of PubMed, Google Scholar, and Web of Science for English-language articles using combinations of the following keywords: mental disorders; persons with psychiatric disorders; drug overdose; poisoning; serotonin syndrome; neuroleptic malignant syndrome; anticholinergic agents/poisoning; cholinergic antagonists/poisoning; psychotropic drugs/adverse effects; substance-related disorders; drug-related side effects and adverse reactions; polypharmacy; suicide, attempted; emergency service, hospital. By embedding toxidrome awareness into routine emergency and psychiatric practice, we aim to expedite treatment and improve patient outcomes.