The Primary Fallacy
When the Conscience is Based on Hopes and Dreams
How do birth control pills “primarily” work?
Scour the internet and you’ll find terms like “primary mode of action” and “primary mechanism of action.”
Here is the distinction:
“Mechanism of action: Biological response derived from a drug administration, due to the interaction of the molecule with specific protein targets. It defines the functional changes on a molecular level, in contrast with ‘mode of action’, which instead refers to the changes observed after administration of a substance on a cellular level.”1 (Liggi, 2014, p. 2030)
To keep things simple, I’m going to use both terms interchangeably. Sorry, molecular biologists.
A more important distinction for this discussion is when and why the word “primary” is supposed to be used when referring to mode or mechanism of action.
The Code of Federal Regulations Title 21 includes extensive definitions, but here’s the gist:
The term “primary mode of action” is reserved for combination products.
Combined-oral-contraceptives like Yaz fit this category because they are comprised of more than one drug.
But progesterone-only-pills like Opill are not a combination product since they are comprised of a single drug. Therefore, you would expect to see simply a “mode of action” described without anything labeled as primary.
Let’s take a look at how these products are described on the web, and then we’ll look at how they’re described by the FDA label…(read more)
Liggi, S., Drakakis, G., Koutsoukas, A., Cortes-Ciriano, I., Martínez-Alonso, P., Malliavin, T. E., Velazquez-Campoy, A., Brewerton, S. C., Bodkin, M. J., Evans, D. A., Glen, R. C., Carrodeguas, J. A., & Bender, A. (2014). Extending in silico mechanism-of-action analysis by annotating targets with pathways: application to cellular cytotoxicity readouts. Future medicinal chemistry, 6(18), 2029–2056. https://doi.org/10.4155/fmc.14.137