Quetiapine

Quetiapine is a second-generation, or atypical, antipsychotic, sold most widely under the brand name Seroquel, approved to treat schizophrenia, bipolar disorder and, as an adjunct, major depressive disorder. It is not a classic recreational drug and is not a controlled substance, but it is heavily sedating and is sometimes misused, often at low doses as a sleep aid and sometimes in institutional or polydrug settings, which is why it appears in a harm-reduction context. Its street reputation as a harmless sleeping pill understates its cardiac and metabolic risks.

Quetiapine acts on multiple neurotransmitter systems, blocking dopamine D2 receptors, the basis of its antipsychotic effect, and prominently serotonin and histamine H1 receptors. Its strong antihistamine action is largely responsible for the heavy sedation and grogginess that drive its non-medical use as a sleep aid. It also blocks certain adrenergic receptors, which contributes to drops in blood pressure. This broad receptor activity explains both its therapeutic effects and its wide side-effect profile.

The most noticeable effects are strong sedation, drowsiness and calm, along with dizziness and dry mouth. Because it lowers blood pressure, standing up can cause lightheadedness or fainting, and it can affect coordination. Unlike many misused drugs it does not typically produce euphoria; the appeal is sedation. Even a single low dose can leave people heavily sedated and impaired well into the next day.

Although quetiapine is not a controlled substance, it is not benign. Its labeling carries warnings about a range of serious effects: it can prolong the heart's QT interval and, particularly in overdose or when combined with other QT-prolonging drugs, contribute to dangerous heart-rhythm disturbances. Atypical antipsychotics as a class raise the risk of high blood sugar, diabetes and significant weight gain with ongoing use, and can cause dangerous drops in blood pressure and falls. Rare but serious reactions include neuroleptic malignant syndrome, a life-threatening reaction with high fever and rigidity, and low white-blood-cell counts. Because quetiapine is a strong sedative, combining it with other central nervous system depressants such as alcohol, opioids or benzodiazepines compounds sedation and respiratory depression and can be dangerous. Its calming reputation masks these risks. Stopping abruptly after regular use can cause withdrawal-like effects such as nausea, insomnia and rebound symptoms, so it is generally tapered under medical guidance. Overdose can cause profound sedation, low blood pressure and heart-rhythm problems and warrants urgent care. If someone is unresponsive, having a seizure, or showing an irregular heartbeat, call 911; Poison Control at 1-800-222-1222 can advise on suspected overdoses. This page has not yet been medically reviewed.