Antipsychotic chlorpromazine equivalents

What the equivalents actually mean

A CPZ equivalent answers the question: "how much of drug X produces roughly the same antipsychotic effect as 100 mg of chlorpromazine?" The problem is that "roughly the same effect" gets defined differently across sources.

• Woods 2003 used minimum effective doses from fixed-dose trials.
• Leucht et al 2014 used both minimum effective dose and near-maximum-effective dose (the 95% ED95 approach).
• Gardner 2010 used expert consensus among prescribers.
• WHO ATC/DDD publishes Defined Daily Doses that reflect assumed maintenance dosing in adults, not equivalence per se.

These give different numbers. For risperidone, Woods says 2 mg = 100 mg CPZ. Gardner's consensus is closer to 3 mg. WHO DDD is 5 mg. All defensible. None precisely right.

Also: oral vs LAI, and total dopamine occupancy differ. Partial D2 agonists (aripiprazole, brexpiprazole, cariprazine) don't fit the same framework because they're intrinsically ceiling-limited. Clozapine equivalents are the most contested because clozapine's antipsychotic effect isn't purely D2-mediated.

The main equivalence table

Values below are approximate mid-range estimates, weighted toward Leucht 2014 where available. Ranges reflect disagreement between sources.

Clozapine's range reflects that some sources treat 50 mg clozapine as 100 mg CPZ (based on receptor occupancy at low doses) while others use 100 mg. Neither captures clozapine's superior efficacy in treatment-resistant illness, which isn't a dose story at all.

Long-acting injectables

LAI equivalence is trickier because you're comparing steady-state plasma levels against oral dosing. The numbers below reflect typical maintenance conversions, not first-dose or loading regimens.

For paliperidone LAI transitions, the manufacturer's conversion chart is more reliable than any equivalence table. Use it.

How to use this in practice

Switching. If you're moving someone from olanzapine 20 mg to risperidone, the CPZ equivalent (400 mg) suggests risperidone 8 mg. That's a starting frame, not a target. Cross-taper to a reasonable dose of the new drug (say risperidone 4 to 6 mg), assess response over 2 to 4 weeks, then adjust. Don't chase equivalence for its own sake.

Dose review. When you inherit a patient on quetiapine 800 mg plus haloperidol 10 mg, adding those up gives 800 + 500 = 1300 mg CPZ-eq. That's a lot. The equivalent number is what makes the conversation with the patient real: "you're on the equivalent of about 1300 mg of chlorpromazine, which is at the high end of what evidence supports."

Reading older trials. Studies from the 1970s through 1990s often report doses in CPZ equivalents. Knowing that 500 mg CPZ-eq is a typical treatment dose and 1000+ is high-dose lets you make sense of the literature.

What not to do. Don't use CPZ equivalents to justify polypharmacy ("their total antipsychotic burden is only 600 CPZ-eq"). Two antipsychotics at 300 mg CPZ-eq each is not clinically equivalent to one antipsychotic at 600 mg CPZ-eq. Receptor coverage, side effect burden, and adherence risk aren't additive that way.

Common questions

Why does clozapine have such a wide equivalent range? Clozapine's antipsychotic effect isn't primarily D2 occupancy at typical doses. It's serotonergic, cholinergic, alpha-adrenergic, and glutamatergic contributions all at once. At 100 mg, D2 occupancy is minimal but clinical effect is real. The equivalence tables just don't capture what clozapine actually does. Some sources put 100 mg clozapine at 50 mg CPZ, some at 100, some at 200. All are defensible depending on what you're modeling. In practice, clozapine's dose is set by response and plasma level (target 350 to 600 ng/mL for treatment-resistant illness), not by CPZ conversion.

Can I use CPZ equivalents to convert between LAIs? Cautiously. For similar drugs (paliperidone monthly to 3-monthly, aripiprazole Maintena to Aristada) use manufacturer conversion tables. For cross-molecule LAI switches, the CPZ equivalent gives a starting point but you should still overlap or plateau because LAI kinetics vary. Aripiprazole Maintena 400 mg monthly is roughly oral aripiprazole 15 to 20 mg, which is roughly 100 to 130 mg CPZ. Paliperidone palmitate 156 mg monthly is roughly oral paliperidone 6 mg, which is roughly 200 mg CPZ. Those aren't interchangeable in dosing decisions.

How much aripiprazole equals a moderate quetiapine dose? Quetiapine 400 mg is about 400 mg CPZ-eq. Aripiprazole at 7.5 mg = 100 mg CPZ suggests you'd need aripiprazole 30 mg to match. That's the top of the label range and often unnecessary. The equivalence framework doesn't work well for partial agonists because their D2 occupancy plateaus. Most patients on quetiapine 400 do fine on aripiprazole 10 to 20 mg during a cross-taper. Titrate to response.

Are equivalents different for negative vs positive symptoms? CPZ equivalents were built on positive symptom control (that's what fixed-dose trials measured). For negative symptoms, primary vs secondary matters more than dose. Reducing overall antipsychotic dose can actually improve secondary negative symptoms driven by D2 over-blockade. Cariprazine has the best negative-symptom evidence among current atypicals, but that's a pharmacology story, not a dose-equivalent one.

Do I use CPZ equivalents in bipolar? Less useful. Antipsychotic dosing in bipolar mania is generally lower than in schizophrenia, and dosing in bipolar depression (quetiapine, lurasidone, cariprazine, olanzapine-fluoxetine combination) follows drug-specific evidence rather than equivalence. Quetiapine 300 mg in bipolar depression isn't the same clinical entity as quetiapine 300 mg in schizophrenia even though the CPZ-eq is identical.

Sources

• Woods SW. Chlorpromazine equivalent doses for the newer atypical antipsychotics. J Clin Psychiatry. 2003;64(6):663-667.
• Leucht S, Samara M, Heres S, et al. Dose equivalents for second-generation antipsychotics: the classical mean dose method. Schizophr Bull. 2014;40(2):314-326.
• Leucht S, Samara M, Heres S, Davis JM. Dose equivalents for antipsychotic drugs: the DDD method. Schizophr Bull. 2016;42(Suppl 1):S90-S94.
• Gardner DM, Murphy AL, O'Donnell H, Centorrino F, Baldessarini RJ. International consensus study of antipsychotic dosing. Am J Psychiatry. 2010;167(6):686-693.
• Andreasen NC, Pressler M, Nopoulos P, Miller D, Ho BC. Antipsychotic dose equivalents and dose-years: a standardized method for comparing exposure to different drugs. Biol Psychiatry. 2010;67(3):255-262.
• WHO Collaborating Centre for Drug Statistics Methodology. ATC/DDD Index. Updated annually.
• Package inserts for cariprazine, brexpiprazole, lumateperone, paliperidone LAI formulations, aripiprazole LAI formulations.

Reviewed against current guidelines as of June 8, 2026. This is not medical advice.