Effectiveness can be described as the result of a medicine’s pharmacological effect (efficacy) in interaction with different contextual factors that occur in real life. In other words, the effectiveness of a medicine can be measured when all real-life interactions occur. These interactions include effect modification, which has an impact on the treatment effect. Contextual factors that interact with the medicine’s pharmacological effect are known as drivers of effectiveness.
There are three levels of contextual factors that interact with the pharmacological effect of a medicine. These relate to the:
- actual use of the medicine
- patient and disease
- healthcare system.
If drivers of effectiveness are not correctly taken into account during a medicine’s development, the effectiveness of the medicine measured in routine clinical practice may differ from that estimated during development, creating an ‘efficacy-effectiveness gap’ (for a definition, see Clarify the Issues).
The figure below illustrates how the three levels of contextual factors may interact with the efficacy of a medicine, resulting in its effectiveness. In reality, when considering specific medicines not all of these potential drivers of effectiveness will be important (i.e. not all variables representing potential interactions with the effect of the medicine will need to be considered as confounders).
Figure. Interactions between drivers of effectiveness and efficacy (image courtesy of Prof Abenhaim)
Ways to better understand and identify the potential drivers of effectiveness for a medicine can be found on Methods to Explore and Identify Drivers of Effectiveness.
Key contributor
Clementine Nordon and Lucien Abenhaim, LASER