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Atypical antipsychotic (second generation) Pregnancy: Use only if essential. Neonatal hyperglycaemia, extrapyramidal effects, and withdrawal.

Olanzapine

Brand names: Zyprexa, Zalasta

Adult dose

Dose: Schizophrenia/Bipolar: 10 mg once daily; range 5–20 mg/day; Acute agitation: 10 mg IM
Route: Oral or IM (acute agitation)
Frequency: Once daily (oral)
Max: 20 mg/day oral; 30 mg/day IM (max 3 IM doses in 24h)
Schizophrenia: start 10 mg OD, range 5–20 mg. Bipolar mania: 15 mg OD. Acute agitation (IM): 10 mg IM, may repeat 2h and 4h later (max 30 mg/24h). Do not give IM olanzapine within 1 hour of IM lorazepam (respiratory depression risk).

Paediatric dose

Route: Oral
Frequency: Once daily
Max: 20 mg/day
13–17 years: 2.5–5 mg OD initially; usual maintenance 5–10 mg OD (max 20 mg). Use lower end of dosing in adolescents. Not licensed for tics/Tourette's.

Dose adjustments

Renal

No dose adjustment required; monitor for accumulation in severe renal failure.

Hepatic

Reduce starting dose in hepatic impairment (10 mg/day max initially).

Clinical pearls

  • Highest weight gain of any antipsychotic — baseline BMI, fasting glucose, lipids mandatory
  • Monitor metabolic syndrome (waist circumference, fasting glucose, lipids, BP) every 6 months
  • Smokers need higher doses — stopping smoking increases olanzapine levels significantly
  • IM olanzapine effective for rapid tranquillisation but avoid with IM benzodiazepines
  • Orodispersible (Velotab) available — useful in patients refusing tablets

Contraindications

  • Narrow-angle glaucoma
  • Hypersensitivity to olanzapine

Side effects

  • Weight gain (significant — most common reason for discontinuation)
  • Metabolic syndrome (hyperglycaemia, dyslipidaemia)
  • Sedation
  • Orthostatic hypotension
  • Extrapyramidal symptoms (less than typical antipsychotics)
  • QT prolongation
  • Tardive dyskinesia (long-term)
  • Hyperprolactinaemia (less than other antipsychotics)

Interactions

  • Benzodiazepines (IM) — severe respiratory depression risk (avoid concurrent IM use within 1 hour)
  • Carbamazepine — reduces olanzapine levels by 50%
  • Fluvoxamine — increases olanzapine levels
  • Smoking — induces CYP1A2; levels can drop 50% in smokers

Monitoring

  • Weight and BMI (monthly for 3 months then quarterly)
  • Fasting glucose (baseline, 3 months, annually)
  • Fasting lipids
  • BP
  • ECG (QT)
  • Prolactin

Reference: BNFc; BNF; NICE CG178; NICE NG185 Bipolar. Verify against your local formulary and the latest BNF before prescribing.

Related

Curated clinical cross-links plus same-class fallbacks.

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