Olanzapin

Olanzapin, known in English as olanzapine, is a second-generation (atypical) antipsychotic used to treat schizophrenia and bipolar disorder. It acts mainly as an antagonist at dopamine D2 and serotonin 5-HT2A receptors, with activity at several other receptors such as 5-HT2C, histamine H1, and alpha-adrenergic receptors. This receptor profile contributes to its effects on psychotic symptoms and mood stabilization, but also to its adverse effect pattern, including weight gain and sedation.

Medical use typically includes treatment of schizophrenia in adults and some adolescents, and management of manic or mixed episodes in bipolar I disorder, with ongoing maintenance therapy in appropriate patients. Olanzapin is also available in a fixed-dose combination with fluoxetine for treatment-resistant depression in some regions, and a long-acting injectable form is used for maintenance in selected patients under specialist care.

Administration and dosing: Olanzapin is available as oral tablets and orodispersible tablets, with an intramuscular form for acutely agitated patients and a long-acting injectable preparation for maintenance. Starting doses commonly begin around 5–10 mg once daily, titrating to about 10–20 mg daily as tolerated and clinically indicated; maximum commonly 20 mg/day. Dosing must be individualized, with adjustments for age, hepatic impairment, and comorbid conditions.

Side effects and safety: Common adverse effects include drowsiness, weight gain, increased appetite, and metabolic changes (glucose and lipid abnormalities). Extrapyramidal symptoms are less frequent than with typical antipsychotics but can occur. Other risks include orthostatic hypotension, anticholinergic effects, and lipid/glucose disturbances, necessitating regular monitoring. A boxed warning notes increased mortality in elderly patients with dementia-related psychosis; use in these patients is not recommended.

Pharmacokinetics and interactions: Olanzapin is extensively metabolized in the liver, mainly by CYP1A2, with contributions from CYP2D6 and CYP3A4. The half-life ranges roughly from 21 to 54 hours. Smoking can induce CYP1A2 and lower olanzapine levels; concomitant CNS depressants may enhance sedation.