Certified Addiction Counselor (CAC) Practice

What defines cross tolerance among psychoactive chemicals?

1. The ability of differing substances to enhance effects

2. The ability of similar substances to substitute for one another

3. The capability to prevent addiction

4. The mechanism through which withdrawal symptoms occur

The correct answer is: The ability of similar substances to substitute for one another

Cross tolerance refers to a phenomenon where tolerance to one substance (usually a psychoactive drug) leads to a similar tolerance effect with another substance, particularly when they share similar pharmacological effects or mechanisms of action. This means that if an individual has developed tolerance to a certain drug, they might exhibit reduced responsiveness to another drug that has similar effects, even if they have not previously used that second drug. For example, if a person has built up a tolerance to alcohol, they may also find that they require higher doses of benzodiazepines (which can act on similar receptors in the brain) to achieve the same effect, even if they have not used benzodiazepines before. This shared mechanism of action is what defines cross tolerance, allowing substances that are pharmacologically related to be interchangeable to a degree when it comes to their effects on the body. The other options do not accurately describe cross tolerance. Enhancing effects of differing substances suggests a synergistic relationship rather than a shared tolerance. The concept of preventing addiction does not pertain to tolerance at all, and while withdrawal symptoms can relate to tolerance, they are not defined by the cross tolerance phenomenon specifically.