synergism
interaction between drugs in which they become more effective than when used alone
Antagonism
drugs interfere with one another and become less effective than when used alone
What is the shape of the zone of inhibition for synergism
bowing outward towards each other
What is the shape of the zone of inhibition for antagonism?
flatting inward, away from each other
Where to measure zone of inhibition
across a non-distorted diameter, if none: non-distorted radius x 2