What is Cross-Tolerance?

What is Cross-Tolerance?

• A. Exposure to one drug is not related to tolerance to other drugs
• B. Tolerance depends on dosage only
• C. Exposure to one drug can cause tolerance to similar drugs
• D. Cross-tolerance only occurs with antibiotics

Answer: (C)

Cross-tolerance happens when the body's adaptations from repeated use of one drug spill over to other drugs that act on the same brain system or have similar effects. The body changes in ways like adjusting receptor sensitivity or altering metabolic enzymes, so another drug with a similar mechanism evokes a weaker effect even if you haven’t used it recently. For example, someone who regularly uses alcohol can show tolerance to other sedatives that boost the same GABA system, or someone tolerant to one opioid may find other opioids less effective. That’s why exposure to one drug can lead to tolerance to similar drugs. The other statements don’t fit because cross-tolerance isn’t about no relationship between drugs, nor is tolerance determined by dosage alone, and cross-tolerance isn’t limited to antibiotics.

Cross-tolerance happens when the body's adaptations from repeated use of one drug spill over to other drugs that act on the same brain system or have similar effects. The body changes in ways like adjusting receptor sensitivity or altering metabolic enzymes, so another drug with a similar mechanism evokes a weaker effect even if you haven’t used it recently. For example, someone who regularly uses alcohol can show tolerance to other sedatives that boost the same GABA system, or someone tolerant to one opioid may find other opioids less effective. That’s why exposure to one drug can lead to tolerance to similar drugs.

The other statements don’t fit because cross-tolerance isn’t about no relationship between drugs, nor is tolerance determined by dosage alone, and cross-tolerance isn’t limited to antibiotics.