Kentucky Licensed Clinical Alcohol And Drug Counselors (LCADC) Practice Test

When one drug blocks or reduces the action of another, that is called antagonism. This type of interaction can occur in several ways: a drug may compete with another for the same receptor (competitive antagonism), or it may change the receptor or signaling pathway so the second drug has a weaker effect (noncompetitive antagonism). It can also involve pharmacokinetic changes that lower the amount of the other drug reaching its site of action. A common example is naloxone blocking opioid receptors to prevent or reverse the effects of opioids like morphine. By contrast, an additive effect means the total effect is simply the sum of each drug’s effect, and a synergistic effect means the combined effect is greater than the sum of their individual effects. The term “independent effect” isn’t the standard label for these interactions.