Dictionary > Synergistic effect

Synergistic effect

synergistic effects - definition and example

Synergistic effect
n., plural: synergistic effects
[ˌsɪnəˈdʒɪstɪk ɪˈfɛkt]
Definition: Effects when chemical substances or biological structures interact resulting in an overall effect that is greater than the sum of individual effects of any of them.

Synergistic Effects Definition

In biology, synergistic effects are the effects when chemical substances or biological structures interact resulting in an overall effect that is greater than the sum of individual effects of any of them. Synergistic effects are the combined effects of at least two substances making an impact that is more significant than both of them could have shown by themselves. Etymology: from Greek “synergos”, meaning “working together”. Compare: antagonistic effect

Examples of Synergistic Effects

  • Skin harm caused by both tobacco smoke and UV radiation is more prominent than by tobacco smoke alone or by UV radiation alone.
  • “Baking soda volcano”‘ activity in science class is another example. The joined activity of vinegar and heating soft drink consolidates to make a seriously percolating emission when mixed.
  • Both carbon tetrachloride and ethanol (ethyl liquor) are harmful to the liver. When administered together, they produce more considerable liver injury than the entirety of their individual impacts on the liver.
  • Barbiturate drugs when taken with general anesthetics, alcohol (acute consumption) narcotic analgesic (pain reliever), and other sedative-hypnotic drugs can lead to greater adverse effects on the central nervous system (CNS) (by causing CNS depression).
  • The toxicity of some insecticides notably pyrethrin (from chrysanthemums) and synthetic pyrethrins (pyrethroids) can be increased many times by the addition of compounds that themselves are not insecticides. These synergists are sesamin, sesamolin, piperonyl butoxide, MGK-264 (bi-cycloheptene dicarboximide), and sesame. Piperonyl butoxide is perhaps the most widely used synthetic pyrethroid synergist.
  • When physicians treat bacterial heart infections with ampicillin and gentamicin. This is done on the grounds that the two antimicrobials target various pieces of the microorganisms, and taking them together kills the microscopic organisms faster, thus speeding up recovery.
  • Cancer treatment presents yet another example of synergism. Patients with cancers are quite frequently put on both chemotherapy and radiation therapy. They work to stop the growth of cancer cells by targeting different parts of the replication process.

Synergy & Synergism

Synergy refers to the interaction of biological structures or entities so that the overall impact will be greater than the sum of individual effects. The extent of the impact is so great that it cannot be reproduced singly. Another related term is synergism. The latter is used in pharmacology. It refers to the condition wherein a set of drugs produce synergistic effects, thereby, enhancing their efficacy. The term, basically, is associated with the notion that “the whole is greater than the sum of its parts”. (Ref. 1)

Synergy in Biology

In biology, synergy is a common phenomenon. It takes many forms. For instance, in ecology, it can take the form of symbiosis, e.g. by cooperation, parasitism, etc. It may also be implied as coevolution in evolutionary biology. In the biochemical world, synergy is manifested in the form of the combined effects of substances, such as drugs. Or, it may be a form of epistasis, genetically-speaking. So let’s take a look at synergy in these various fields.

Synergy in Ecology

Cooperation, a type of symbiosis, is an ecological synergy in a way that individuals in the association work together to bring about positive effects. An example of this would be ant and bee colonies. These social insects have distinctive roles and castes in their colony.  They communicate with each other chiefly through chemical signals picked up by their antennae. Colobopsis explodens, for instance, display an interesting behavior referred to as autothysis. These ants will explode (thus, the name) their body at will while wrapped around to their enemy. This suicidal act is an effort to defend their nest. Autothysis is also seen in certain species of termites wherein soldier termites will rupture their body to act as a blockade to tunnels, thereby preventing invaders from entering their nest. (Ref. 2)

Cooperation that leads to synergism is also exhibited by the colony of predatory myxobacterial species, Myxococus xanthus. M. xanthus is a soil bacterium that prey on other bacteria. Together, they form a cooperative hunting group (colony) through the soil. They secrete digestive enzymes as they encounter and feed on bacteria.  Through colonies, they are able to feed even much larger prey and jointly secrete digestive enzymes much more than that produced singly, which has the disadvantage of getting dissipated through the soil. (Ref. 1, 3)

Myxococcus xanthus - synergy by cooperation

Myxococcus xanthus – synergy by cooperation. Credit: Devangam,  Microbewiki.kenyon.edu.

The presence of two or more kinds of parasites within the host exemplifies pest synergy. So for instance, the presence of two different kinds of parasitic worms would produce synergistic adverse effects that are far greater than the effects produced by each. The impact, therefore, correlates with density. This is also apparent even in infection. The host that harbors pathogenic bacteria or viruses may or may not show symptoms of the infection as the impact of the presence of the pathogens will depend on the pathogens’ size or population density.

Synergy in Evolutionary Biology

The phenomenon of synergy is employed in Evolutionary Biology in an attempt to explain the progressive evolution of complexity among organisms through time. Referred to as the Synergism Hypothesis,  it postulates that synergism serves as the functional basis for the evolution of complex systems in nature, including human societies. (Ref. 1) Certain associations formed together by two or more species are so great that they tend to coevolve together through time. For example, the insects and flowers they pollinate coevolve by acquiring traits that made them relatively more complex than their ancestors as driven by selection pressures present in their environment.

Synergy in Biochemistry

Synergy at the biomolecular level is exemplified by certain enzymes working together producing synergistic effects. At the cellular level, this is demonstrated by certain hormones, especially those involved in a positive feedback loop. For example, oxytocin is produced incrementally during childbirth to induce labor contractions. As more oxytocin is released, the muscle contractions are intensified until the neonate is pushed outside the birth canal.

In pharmacology, drug synergism happens when the effects of two or more different kinds of drugs are amplified when they are administered jointly. Their impact is greater than their combined effects. For instance, drug A produces an effect of 30% while drug B produces an effect of 20%. When combined, their synergistic effects are at 75%, which is greater than the sum of their independent effects, which is 50%.

Examples are as follows:

  • The synergistic effects of penicillin and aminoglycoside on the cell wall damage of certain gram-positive bacteria
  • Combined potency of aspirin and caffeine in providing greater pain relief than when taken alone
  • Probenecid drug prolonging the effects of penicillin by delaying the latter’s renal excretion (Ref. 4)



Toxicological synergy refers to the investigation of the antagonistic impacts of synthetic compounds or physical operators on living life forms. The conventional meaning of toxicology is “the study of toxins”. Toxicologic cooperative energy is of worry to people in general and administrative organizations since synthetic substances exclusively viewed as protected would present unsuitable well-being or biological danger when the introduction is to a mix.

The toxicity of certain insecticides can be increased several times by the presence of other compounds that are not insecticides, per se. Referred to as synergists, compounds such as piperonyl butoxide, sesamin, sesamolin, bi-cycloheptene dicarboximide, and sesamex, augment the insecticidal activity of pyrethrin. (Ref. 5)

Synergy in Genetics

Epistasis refers to the interaction of the genes at two or more loci. Together, they make the phenotypic expression of another gene. The term synergistic epistasis refers to the type of epistasis wherein the effect of two mutations on fitness is greater than what they would have produced when alone.

Try to answer the quiz below to check what you have learned so far about Synergistic Effects.


Choose the best answer. 

1. Cooperation, a form of symbiosis, is an ecological synergy. The more individuals work together the more there are cumulative positive effects.

2. Pest synergy pertains to a form of synergy wherein the presence of two or more kinds of parasites could lead to more adverse effects than when they are present without the others.

3. Drug synergism happens when the effects of two or more different kinds of drugs cancel each other's effects.

4. The potency of aspirin and caffeine increases when combined, providing greater pain relief than when taken alone.

5. Synergistic epistasis is when the genes interact and together cause more effects than they would have produced when alone.

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  1. Corning, P. A. (1998). “The synergism hypothesis”: On the concept of synergy and its role in the evolution of complex systems. Journal of Social and Evolutionary Systems21(2), 133–172. https://doi.org/10.1016/s1061-7361(00)80003-x
  2. Newly Discovered Exploding Ants – Colobopsis explodens – Biology Online Archive Article. (2020, March 6). Biology Articles, Tutorials & Dictionary Online. https://www.biologyonline.com/articles/newly-discovered-exploding-ants-colobopsis-explodens‌
  3. Myxococcus xanthus – microbewiki. (2011). Kenyon.Edu. https://microbewiki.kenyon.edu/index.php/Myxococcus_xanthus#:~:text=Myxococcus%20xanthus%20is%20a%20soil,can%20take%20up%20and%20metabolize.‌
  4. Tripathi, K. D. (2013). Essentials of Medical Pharmacology G – Reference, Information and Interdisciplinary Subjects Series. JP Medical Ltd. p. 931.
  5. Amdur, M. O., Doull, J., & Klaassen, C. D. (1993). Casarett and Doull’s Toxicology: The Basic Science of Poisons, 4th Edition. ResearchGate; Lippincott, Williams & Wilkins. https://www.researchgate.net/publication/232211057_Casarett_and_Doull’s_Toxicology_The_Basic_Science_of_Poisons_4th_Edition‌


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