chlorpromazineR: Convert antipsychotic doses to chlorpromazine equivalents

Studies investigating or controlling for the impact of antipsychotic medications often need to quantify the amount of medication to which an individual is or has been exposed. As different antipsychotics have different potencies, the task is more complicated than using each medication’s daily dosage in milligrams, for example. chlorpromazineR is an R package to calculate dose equivalents for common oral and injectable antipsychotic medications based on conversion factors from the published literature. We do not propose to suggest which conversion factors are appropriate to use, or how to interpret the converted data. All users should also refer to the papers from which the conversion factor data originates to determine whether the use of such data is appropriate for their study.

We hope that this package is of use to scientists who do clinical research involving antipsychotic medications. Specifically, the goals of this package are:

• to improve transparency and consistency in calculating chlorpromazine equivalents,
• to reduce human error and improve accuracy,
• and to simplify workflows for large datasets, as from chart reviews of electronic health records.

For further details and usage, please see the walkthrough vignette.

This results from this package should be double checked for accuracy when used in production. We welcome feedback--please contact via eb@ericebrown.com or file an issue.

Installation

The CRAN release version (recommended) can be installed via the command: install.packages("chlorpromazineR").

The development version of this package can be installed via the command: devtools::install_github("ropensci/chlorpromazineR").

Usage

Once installed, load package with library(chlorpromazineR). The package's main conversion functions are documented and usage and examples can be seen with help(to_cpz) and help(to_ap). It is strongly recommended to read the articles from which the keys are derived, and to verify that the program's output is producing results as expected. This package facilitates bulk conversion, but should be verified to ensure it produces the results as expected.

Online calculator

An online calculator using this package is available as a shiny app.

Convert data to chlorpromazine equivalents

participant_ID <- c("P01", "P02", "P03", "P04")
age <- c(42, 29, 30, 60) # not used in calculation
antipsychotic <- c("olanzapine", "olanzapine", "quetiapine", "ziprasidone")
dose <- c(10, 12.5, 300, 60)
example_oral <- data.frame(participant_ID, age, antipsychotic, dose, 
                           stringsAsFactors = FALSE)
to_cpz(example_oral, ap_label = "antipsychotic", dose_label = "dose", 
       route = "oral")

Disclaimer

This package is not for clinical use. The authors assume no liability. All work must be verified independently. Use at own risk.

Licence

Copyright (C) 2019-2021 Eric E. Brown. This software is licensed under the GPL-3.

Citation

If you use this package in your scientific paper, please cite this package and the original papers from which the conversion factors are derived. The references can be viewed by using the built-in help function, e.g. help(gardner2010), and as listed below. In addition, a spreadsheet-based tool facilitating dose equivalence conversion has been published by Leucht et al. (2020).

Davis, J. (1974). Dose equivalence of the anti-psychotic drugs.
Journal of Psychiatric Research, 11, 65-69.
<https://doi.org/10.1016/0022-3956(74)90071-5>

Gardner, D. M., Murphy, A. L., O’Donnell, H., Centorrino, F., & 
Baldessarini, R. J. (2010). International consensus study of 
antipsychotic dosing. The American Journal of Psychiatry, 167(6),
686–693. <https://doi.org/10.1176/appi.ajp.2009.09060802>

Leucht, S., Samara, M., Heres, S., & Davis, J. M. (2016). Dose
Equivalents for Antipsychotic Drugs: The DDD Method. Schizophrenia
Bulletin, 42(suppl_1), S90–S94. <https://doi.org/10.1093/schbul/sbv167>

Leucht, S., Crippa, A., Siafis, S., Patel, M., Orsini, N. & Davis, J. M. 
(2020). Dose-Response Meta-Analysis of Antipsychotic Drugs for Acute 
Schizophrenia. American Journal of Psychiatry. 117(4).
<https://doi.org/10.1176/appi.ajp.2019.19010034>

Woods, S. (2003). Chlorpromazine Equivalent Doses for the Newer
Atypical Antipsychotics. Journal of Clinical Psychiatry. 64(6).
663-667. <https://doi.org/10.4088/JCP.v64n0607>