Which term best describes the interaction where the combined effect is greater than the effects of either substance alone?

• A. Synergism
• B. Antagonism
• C. Tolerance
• D. Metabolism

Answer: (A)

When two substances interact in a way that the overall effect is larger than what either would produce alone, that interaction is called synergy. This means the joint action is more than just adding the two effects together; they amplify each other, producing a bigger impact than expected from either substance by itself. Synergy can arise from different mechanisms, such as both substances acting on the same target to strengthen the response, or one substance changing how the other is processed or available in the body to boost its effect. This concept is different from an additive interaction, where the total effect equals the sum of the individual effects; or from antagonism, where one substance dampens the effect of the other. It’s also distinct from tolerance, which is a diminished response to a substance with repeated use, and from metabolism, which describes how the body processes drugs.