Which term describes a combined effect equal to the sum of each drug’s effect?

• A. Additive Action
• B. Synergism
• C. Potentiation
• D. Antagonism

Answer: (A)

The concept here is additive action. When two drugs with active effects that contribute independently are used together, the total effect is essentially the sum of each drug’s effect. There’s no enhancement beyond simple addition or suppression of the other’s action. For example, if Drug A lowers a fever by a certain amount and Drug B lowers the fever by the same amount, the combined effect is about twice that amount.

If the combination produces more than the sum, that would be synergism. If one drug doesn’t have an effect on its own but increases the effect of another, that’s potentiation. If one drug reduces or blocks the effect of another, that’s antagonism.