| Level I | Good quality evidence |
Systematic review of RCTs with consistent findings High quality individual RCT |
| Level II |
Limited quality patient orientated evidence |
Systematic review of lower quality studies or studies with inconsistent findings Low quality clinical trial Cohort studies Case-control studies |
| Level III | Other |
Consensus guidelines, extrapolations from bench research, usual practice, opinion, disease-oriented evidence (intermediate or physiologic outcomes only), or case series |
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Olanzapine, oral: Krause M, Zhu Y, Huhn M, Schneider-Thoma J, Bighelli I, Nikolakopoulou A, Leucht S. Antipsychotic drugs for patients with schizophrenia and predominant or prominent negative symptoms: a systematic review and meta-analysis. Eur Arch Psychiatry Clin Neurosci. 2018 Oct;268(7):625-639. https://www.ncbi.nlm.nih.gov/pubmed/29368205
Olanzapine, oral: National Department of Health: Affordable Medicines, EDP-Adult Hospital level. Medicine Review: Olanzapine, oral for schizophrenia and related disorders, June 2019. http://www.health.gov.za/