Quetiapin

Quetiapin is an atypical antipsychotic medication used to treat schizophrenia, bipolar disorder (including manic and depressive episodes), and as an adjunctive treatment for major depressive disorder. It is available in immediate‑release and extended‑release tablet forms, often marketed under the names Quetiapin IR and Quetiapin XR. The drug is typically started at a low dose and adjusted based on effectiveness and tolerability.

Pharmacology and pharmacokinetics: Quetiapin acts mainly as an antagonist at dopamine D2 and serotonin 5-HT2A receptors, which is thought to help reduce psychotic and mood symptoms. It also has antihistaminic and some alpha‑adrenergic blocking activity, contributing to sedation and other effects. Quetiapin is metabolized in the liver primarily by the CYP3A4 enzyme. The extended‑release formulation is designed to provide a slower release over the day, which can affect dosing and side effects.

Clinical uses and considerations: In schizophrenia, quetiapin can help with psychotic and mood symptoms. In bipolar disorder, it is used for manic or mixed episodes and for bipolar depression. For major depressive disorder, it is used as an adjunctive therapy when symptoms persist despite antidepressants. It may be prescribed off-label for sleep in some cases due to its sedating effects. Caution is advised in elderly patients with dementia‑related psychosis, as antipsychotics in this population are associated with increased mortality. Suicidality risk should be monitored in mood disorders.

Safety and monitoring: Common side effects include sleepiness, dizziness, weight gain, and metabolic changes such as increased blood sugar and lipids. Less commonly, movement disorders or restlessness can occur. Quetiapin can interact with other medications that affect liver enzymes, particularly CYP3A4 inhibitors or inducers, and with other central nervous system depressants. Regular monitoring of weight, glucose, lipids, and symptoms is recommended.