Which statement describes a synergistic pharmacologic interaction?

• A. The combined effect exceeds the sum of the individual effects.
• B. The combined effect equals the sum.
• C. The combined effect is less than the sum.
• D. The drugs cancel each other.

Answer: (A)

Synergy happens when two drugs, taken together, produce an effect that is greater than adding their separate effects. This means the combination boosts overall activity beyond what you’d expect if you just added each drug’s independent effects. It can occur because the drugs act on different targets that amplify the response or because one drug enhances the other's action at the site of effect. For example, two agents with distinct mechanisms may work together to kill a pathogen more effectively than either would alone. By contrast, if the combined effect were just equal to the sum of the two, that would be additive; if it were less than the sum, or if they counteract each other, that would be antagonistic. So the statement that describes a synergistic interaction is that the combined effect exceeds the sum of the individual effects.