Adults

For schizophrenia: Initially 10 mg once daily, adjusted based on clinical response, typically 5-20 mg/day. For bipolar mania: Initially 10-15 mg once daily, adjusted to 5-20 mg/day. A 50 mg dose is exceptionally high and should only be used under strict medical supervision for resistant cases.

Elderly

A lower starting dose (e.g., 5 mg/day) and slower titration may be considered due to potential for increased sensitivity and risk of adverse effects.

Renal_impairment

No specific dosage adjustment is required for mild to moderate renal impairment, but caution is advised. For severe impairment, dose adjustment may be necessary based on clinical judgment.

Onset

Initial effects may be noticed within a few days, but full therapeutic effects for schizophrenia or bipolar disorder may take several weeks.

Excretion

Approximately 57% of the dose is excreted in the urine and 30% in the feces.

Half life

The elimination half-life is approximately 21 to 54 hours.

Absorption

Well absorbed after oral administration, bioavailability is approximately 60%. Peak plasma concentrations are reached in 5-8 hours.

Metabolism

Extensively metabolized in the liver, primarily by glucuronidation and by the cytochrome P450 enzymes CYP1A2 and CYP2D6. The major circulating metabolites are inactive.

Antihypertensives

Potentiation of orthostatic hypotension.

Carbamazepine (CYP1A2 inducer)

Decreased olanzapine plasma levels, dose increase may be necessary.

Fluvoxamine (CYP1A2 inhibitor)

Increased olanzapine plasma levels, dose reduction may be necessary.

Alcohol and other CNS depressants

Enhanced CNS depressant effects, increased sedation.