Isabel had been taking Valium, a benzodiazepine, for a few years to calm her nerves and help her sleep. She had her dosage increased by her doctor because her previous dosage wasn’t helping her sleep at night anymore. One night, she went out with her husband for his company’s annual Christmas party. She had never been much of a drinker, but that evening she wanted to enjoy a few cocktails. She was very careful not to mix her Valium with alcohol, as her doctor had warned her. Towards the end of the evening, Isabel realized that she had had at least 5 cocktails and didn’t feel drunk at all. Which term may best describe why this happened?
a. Cross dependence
b. Cross tolerance
c. Up-regulation
d. Co-transmission

Cross - tolerance may be defined as the phenomena in which the tolerance of the one chemical increases the tolerance of the other chemical. This cross tolerance can occur in case of the multiple drugs in the individual.

The cross tolerance especially occurs in the different drugs that have similar functions or may act on the same receptors. Isabel drugs shows the cross tolerance with the alcohol as these includes the tolerance for each other and do not increase the drunkenness .

Thus, the correct answer is option (b).