(noun. /SIN-er-jee/)
by Amanda Linke
What does it mean?
Synergy is the interaction between two or more substances to produce a combined effect greater than the sum of their separate effects.
When a patient has cancer or an infection, they will usually receive multiple drugs to treat their condition. Therefore, scientists are very interested in studying how those drugs interact together, and how to make combinations that better kill cancer cells or bacteria.
For example, let’s say Drug A (red) will kill 50% of the population and Drug B (blue) will kill another 50% of the population. In a population of 1000 bacteria, Drug A would kill 500 bacteria, but then there are only 500 bacteria left for Drug B to target. Therefore, Drug B would kill 50% of 500, or 250 bacteria. After both drug treatments, there would be 250 living bacteria and 750 dead bacteria, which is 75% killing of the starting population. This shows how even if two drugs could kill 50% of a population, added together they only kill 75% of the total, not 100%.
Therefore, scientists developed the idea of synergy: Can two drugs work together to kill completely independent populations so the combination can achieve more killing effects than normal? Can we develop the perfect treatment strategy to target more than the sum of the individual parts? The key to developing a good drug combination is to decrease the overlapping population (gray) affected by either drug to maximize their individual effects.
How do I use it in a sentence?
Anti-inflammatory drugs and opioids given together synergize to decrease chronic pain for some patients.
Combining Drug A (50% kill effect) with Drug B (50% kill effect) can lead to three potential drug interactions: 1) Antagonism, where the drugs affect similar populations (60% kill effect); 2) Additivity, where the drugs have 50% overlapping affected populations (75% kill effect); or 3) Synergy, where drugs affect very different populations (90% kill effect). In perfect antagonism the drugs would affect the exact same population, leading to an overall decrease in effect (50% kill effect). In perfect synergy the drugs would affect completely independent populations, leading to an increased effect (100% kill effect). Image is the author’s own work.
Etymology
Synergy comes from the Greek word sunergos, meaning “working together.”
Related terms
Additivity: interaction between two or more substances to produce a combined effect equal to the sum of their separate effects (average population overlap).
Antagonism: interaction between two or more substances to produce a combined effect less than the sum of their separate effects (high population overlap).
Misconceptions (about word usage)
Many pharmacologists will use the word synergy when they observe additivity. True synergy is rare in drug discovery and must be mathematically proven using the Loewe Additivity (which looks at percent effects like above) or Bliss Independence (which focuses on drug dosages) models.
Fields of study in which this word is commonly used
Cancer biology, Pharmacology, Drug Discovery.
