Pharmaceutical Terms: Efficacy, Effectiveness and Efficiency


In this brief article, we explain the different pharmaceutical terms used to explain the effect.

 Efficacy, Effectiveness and Efficiency


In essence its getting a specific effect done without consideration the resources needed or used to reach it, this is the opposite of efficency. Efficacy  is reaching (via procedure, service or intervention) a specific goal to produce a desired effect with the key word IDEAL CONDITIONS ( in lab conditions,  controlled environment and under professionals).

In an efficacy system or person is one who achieves acceptable levels of performance (outcome, output) with relatively high inputs (resources, time, money) are consumed to achieve this.

Example: The efficacy of vaccine A was achieved under ideal lab circumstances, yet, its effectiveness needs to be shown.

  • Efficacy is the extent to which a specific intervention, procedure, or service produces the desired effect, under ideal conditions (controlled environment, lab circumstances). Efficacy = Effectiveness. Only the circumstance.
  •  Efficacy is getting things done, i.e. meeting targets.  Efficacy is the ability to produce a desired amount of the desired effect, or success in achieving a given goal.  Contrary to efficiency, the focus of efficacy is the achievement as such, not the resources spent in achieving the desired effect.



  • Being effective means achieving organizational goals. Effectiveness comes first.
  • Effectiveness is the extent to which planned outcomes, goals, or objectives are achieved as a result of an activity, strategy, intervention or initiative intended to achieve the desired effect, under ordinary circumstances (not controlled circumstances such as in laboratory).
    Example: A vaccine is effective when it is capable to produce the desired effect (protection against disease) in the population, under ordinary circumstances.
  • Effectiveness is doing “the right” things, i.e. setting right targets to achieve an overall goal (the effect).  In his book “The Effective Manager” Peter Drucker claims that effectiveness is a very important discipline which “can be learned and must be learned.” We could easily learn what the right things are.  But this is not enough to be effective.  As Nicholay Haitov said in “Men Times” – it’s one thing to wish (know), another – to be capable of doing it and third and fourth – to do it. Most important is the fourth – to do it.  Effectiveness is not a destination, it is a journey. We will always need to find the right things and we will always have to do them.  Our success will be measured by our results, not by our plans, intentions or promises.


  • Being efficient means achieving goals with little wasted resources.
  • Efficiency is the ratio of the output to the inputs of any system. An efficient system or person is one who achieves higher levels of performance (outcome, output) relative to the inputs (resources, time, money) consumed.
    Examples: Worker A moved 16 boxes from the truck to the store in one hour and worker B moved 9 boxes in one hour. Worker A is more efficient than worker B. Car T uses 10 gallons to travel 150 miles, car F uses 13 gallons to travel 150 miles. Car T is more fuel efficient than car F.
  • Efficiency is doing things in the most economical way (good input to output ratio).  Some colleagues do their job with 300 telephone calls and in 900 minutes (Efficient), while others do the same job with 500 calls and 2000 minutes (Not Efficient).

effectiveness, efficiency, efficacy, leaderPostulate on effectiveness: what is effective is not necessarily efficacious, and what is efficacious is not necessarily efficient.



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Dr. Mohsen Saeed Ozaibi

A Dentist, Professional Blogger and Owner on Graduated in 2009 with a Bachelor Degree in Dental Science from Misr International University. A Pioneer in Digital Dental Content Publishing.

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