Psychiatric Pharmacy Essentials: Antipsychotic Dose Equivalents

Antipsychotic dose equivalents may be utilized when switching between antipsychotics or when comparing different medications. Multiple methods are used to calculate antipsychotic dose equivalences, each with their own strengths and limitations. Variation in receptor binding profiles of newer agents, changes to methodology in clinical trials over the decades, and lack of dose response data for older agents means no one method will apply to all available agents. Furthermore none of the available methods take into account a patient’s acuity status, specific physical and medical condition(s), or history of previous antipsychotic exposure. Equivalent doses are difficult to determine and often incorrect therefore the information below should be paired with caution and clinical judgement. Methods which currently exist consider schizophrenia or psychosis dosing and may not accurately translate to other psychiatric diagnoses. It should also be noted that dose equivalency guidance may not predict individual patient efficacy or tolerability. An awareness and comparison of multiple methods is required for clinical decision making, and has been included in the table and references below.  The link to the multi-method dose equivalent calculator referenced in Leucht et al. (2020) has also been included to aid in calculation of medications or formulations not included in the table below.

How should I convert doses between different antipsychotics?1-6

Oral Antipsychotic Dose Equivalents (based on olanzapine)

Generic Brand   DDD1,2 ED953 MED4 CMD5
First Generation Antipsychotics          
Chlorpromazine Thorazine©   30mg N.A N.A 38.9mg
Fluphenazine Prolixin©   1mg N.A N.A 0.5mg
Haloperidol Haldol©   0.8mg 0.42mg 0.53mg 0.6mg
Loxapine Loxitane©   10mg N.A N.A N.A
Perphenazine Trilafon©   3mg N.A N.A 3.5mg
Pimozide Orap©   0.4mg N.A N.A N.A
Thioridazine Mellaril©   30mg N.A N.A 37.1mg
Thiothixene Navane©   3mg N.A N.A 2.0mg
Trifluoperazine Stelazine©   2mg N.A N.A 1.1mg
Second Generation Antipsychotics          
Aripiprazole Abilify©   1.5mg 0.76mg 1.33mg 1.41mg
Asenapine Saphris©   2mg 0.99mg 1.33mg 0.89mg
Brexpiprazole Rexulti©   N.A 0.22mg N.A N.A
Cariprazine Vraylar©   N.A 0.5mg N.A N.A
Clozapine Clozaril©   30mg N.A 40mg 30.62mg
Iloperidone Fanapt©   N.A 1.33mg 1.07mg N.A
Lurasidone Latuda©   6mg 9.69mg 5.33mg N.A
Lumateperone Caplyta©   N.A N.A N.A N.A
Olanzapine Zyprexa©   1mg 1mga 1mg 1mg
Paliperidone Invega©   0.6mg 0.88mg 0.40mg N.A
Quetiapine Seroquel©   40mg 31.78mg 20mg 32.27mg
Risperidone Risperdal©   0.5mg 0.41mg 0.27mg 0.38mg
Ziprasidone Geodon©   8mg 12.29mg 5.33mg 7.92mg

Abbreviations: ED95 = 95% Effective Dose;  OLZ = olanzapine;  MED = Minimum Effective Dose; DDD = Defined Daily Dose; CMD = Classical Mean Dose;  ICSAD = International Consensus Study of Antipsychotic Dosing, CPZ = chlorpromazine; n.a = not available.
a ED95 equivalence based off dose-response for predominant positive symptoms

Definitions:

Defined Daily Dose: assumed average maintenance dose per day for a drug used for its main indication for adults2
95% Effective Dose: the mean dose that produces 95% of maximum symptom reduction3
Minimum Effect Dose: the lowest fixed dose consistently more efficacious than placebo4
Classical Mean Dose: calculates mean doses utilized in randomized, double-blind, flexible dose available studies of antipsychotics5

Multi-method Dose Equivalent Calculator:3

Antipsychotic Dose Conversion Website

Reviewer 1:  Leah Rickert, PharmD, BCPP
Reviewer 2: Austin Smith, PharmD, BCPP
2024-2025 AAPP Resident and New Practitioner Committee

References

  1. WHO Collaborating Centre for Drug Statistics Methodology. (2024) ATC/DD Index 2024. Accessed August 30,2024. [Weblink]
  2. Leucht, S., Samara, M., Heres, S., & Davis, J. M. (2016). Dose Equivalents for Antipsychotic Drugs: The DDD Method. Schizophrenia bulletin, 42 Suppl 1(Suppl 1), S90–S94. [Weblink]
  3. Leucht, S., Crippa, A., Siafis, S., Patel, M. X., Orsini, N., & Davis, J. M. (2020). Dose-Response Meta-Analysis of Antipsychotic Drugs for Acute Schizophrenia. Am J Psychiatry, 177(4), 342–353. [Weblink]
  4. Leucht, S., Samara, M., Heres, S., Patel, M. X., Woods, S. W., & Davis, J. M. (2014). Dose equivalents for second-generation antipsychotics: the minimum effective dose method. Schizophrenia bulletin, 40(2), 314–326. [Weblink]
  5. Leucht, S., Samara, M., Heres, S., Patel, M. X., Furukawa, T., Cipriani, A., Geddes, J., & Davis, J. M. (2015). Dose Equivalents for Second-Generation Antipsychotic Drugs: The Classical Mean Dose Method. Schizophrenia bulletin, 41(6), 1397–1402. [Weblink]
  6. Patel, M. X., Arista, I. A., Taylor, M., & Barnes, T. R. (2013). How to compare doses of different antipsychotics: a systematic review of methods. Schizophrenia research, 149(1-3), 141–148. [Weblink]