Olanzapine (Olazax, Zalasta, Zyprexa)
Mechanism of action
Antipsychotic (atypical).
Antagonises several receptors including dopamine receptor D1, D2, D3 and D4, serotonin receptor 5HT2A, 5HT2C, 5HT3, 5HT6, alpha-1 adrenergic receptor, histamine receptor H1 and muscarinic receptors.
Block of D2 receptor, specifically in the mesolimbic pathway, and serotonin 5HT2A receptor in prefrontal cortex are mainly responsible for the antipsychotic effects of olanzapine.
Indications and dose
Pharmacokinetics
Onset of action: 15–45 minutes
Half-life of elimination: 21–54 hours (30 hours on average)
Metabolism: Hepatic
Elimination: Mainly through metabolism, only 7 % as an unchanged drug
Directions for administration
Starting dose may be adjusted within the range 5–20 mg/day after clinical reassessment.
Lower starting dose (5 mg) is recommended in patients with severe renal/hepatic impairment.
Metabolism of olanzapine may be induced by smoking although it is not recommended to routinely change the dosage for smokers.
Medicinal forms
Tablets – 2.5 mg, 5 mg, 7.5 mg, 10 mg, 15 mg, 20 mg
Side-effects
Somnolence, dizziness
Weight gain
Eosinophilia, leukopenia, neutropenia
Elevation of prolactin, cholesterol, glucose, and triglyceride levels
Transient (asymptomatic) elevations of hepatic aminotransferases
Dyskinesia, parkinsonism
Orthostatic hypotension
Anticholinergic effects
References
