This Antipsychotic Conversion Calculator is a web tool that converts a given oral antipsychotic daily dose into a chlorpromazine-equivalent value and estimates the approximate equivalent dose of another antipsychotic, using commonly cited dose-equivalence conventions and published conversion methods.

What this calculator does and why it exists

Switching antipsychotics or comparing total antipsychotic exposure is a common clinical and research need. Because antipsychotics differ widely in potency, a simple milligram-to-milligram comparison is misleading. The calculator translates an initial drug dose into a chlorpromazine-equivalent (CPZ) — a commonly used common denominator in literature — and then converts that CPZ back into a dose of the target antipsychotic. This lets clinicians, pharmacists, and researchers get a quick, approximate idea of relative potency and dosing when considering switches or cumulative exposure.

The conversion method (brief, practical)

There is no single universally accepted conversion method; several methods are used in the literature, including expert consensus tables, the Defined Daily Dose (DDD) method, and meta-analytic equivalence estimates. The calculator uses a set of commonly cited conversion factors (sourced from peer-reviewed summaries and comparative tables) to approximate how many milligrams of chlorpromazine correspond to 1 mg of each antipsychotic. For example, commonly-used conversion conventions treat 2 mg haloperidol ≈ 100 mg chlorpromazine (so 1 mg haloperidol ≈ 50 mg CPZ), and 5 mg olanzapine ≈ 100 mg chlorpromazine (so 1 mg olanzapine ≈ 20 mg CPZ). These are approximations drawn from the published literature and standard clinical references.

Step-by-step: How to use the calculator

1. Select the “From” drug — choose the antipsychotic the patient is currently taking.
2. Enter the daily dose (mg) — type the total daily oral dose. For split doses (e.g., 10 mg morning and 10 mg evening), enter the sum.
3. Select the “To” drug — choose the antipsychotic you want to compare with or switch to.
4. Press Convert — the tool immediately displays:
   • The chlorpromazine equivalent (mg CPZ) for the entered dose.
   • The estimated dose (mg) of the target drug that corresponds to the same CPZ.
   • A small bar chart illustrating the original dose, the CPZ equivalent, and the estimated target dose for visual comparison (Plotly.js renders the chart).
5. Interpret with caution — treat results as approximate starting points for clinical judgment, not prescriptive values.

Practical tips and clinical considerations

• Use the calculator as a guide, not a prescription tool. Always consider patient-specific factors: prior response, side-effect sensitivity (EPS, metabolic effects), age, hepatic/renal function, drug interactions, and smoking status.
• Different methods give different numbers. Literature comparisons show variability by method (minimum effective dose method, DDD, meta-analyses). If switching, cross-check with local guidelines, product labeling, and specialist advice.
• Depot/LAI formulations and parenteral routes require different handling; this calculator focuses on common oral formulations.
• When in doubt, taper and monitor. Cross-tapering protocols and slow titration may be safer than abrupt switches, depending on the medications involved. Australian and other switching tools provide stepwise guidance for many switches.

Technical notes (for editors and site owners)

• The calculator uses Plotly.js for a simple bar chart; the UI is intentionally compact and constrained to max-width:760px so it fits typical WordPress content columns placed between sidebars.
• The background is white (per your specification) and styles are inline for maximum compatibility with WordPress custom code blocks.
• The conversion table is editable in the JavaScript block — you can update factor values to match your preferred conversion source or local guidance.

Limitations and safety/disclaimer

Dose equivalence estimates are inherently imprecise. Different studies and conversion methods produce different equivalency estimates, and some drugs (e.g., clozapine, partial agonists like aripiprazole) present special interpretation challenges. This tool is for informational use only. It must not replace clinical judgment, individual patient assessment, or specialist consultation. Always consult a psychiatrist or pharmacist before changing antipsychotic therapy.

References and methodological sources

• Leucht S, et al. Dose Equivalents for Second-Generation Antipsychotic Drugs (systematic comparisons). (peer-reviewed meta-analytic sources).
• Woods SW. Chlorpromazine Equivalent Doses for the Newer Atypical Antipsychotics. Journal of Clinical Psychiatry (commonly-cited reference). 
• Defined Daily Dose (DDD) comparative analyses and conversion tables (used to calculate several baseline CPZ equivalences).
• Antipsychotic switching tool and practical switching guidance (Australian Prescriber).

FAQ (short)

Q: Is the calculator safe to use for prescribing?
A: No — it’s informational only. Use clinical judgment and consult a clinician before changing therapy.

Q: Why do different sources give different equivalents?
A: Different methods (trial-based, DDD, expert consensus) and variations in study populations, dosing ranges, and potency metrics produce different estimates.

Q: Does the calculator support injections or depot formulations?
A: Not directly. This calculator is designed for common oral dosing. Depot formulations require different conversion handling.

Q: Can I add more drugs or change conversion factors?
A: Yes — the conversion factors are defined in the JavaScript cpzPerMg object and can be edited to reflect preferred references.

Q: Are long-acting injectables (LAIs) comparable using CPZ?
A: LAIs are typically converted with specific equivalence tables and schedules — consult product-specific conversion guidance and clinical references.