What phenomenon can develop between natural and synthetic opiates?

Cross tolerance is the correct choice because it refers to a situation where tolerance to one substance results in a decreased response to a related substance. In the context of opiates, both natural and synthetic opiates can bind to the same receptors in the brain, leading to diminished effects over time. For example, an individual who has developed a tolerance to a natural opiate may find that they require higher doses of a synthetic opiate to achieve the same level of pain relief or euphoria.

This phenomenon occurs due to the biological mechanisms involved in the way the body processes and responds to these substances. When the body becomes accustomed to the presence of one opiate, the receptors may become less responsive, or the number of available receptors may decrease. As a result, tolerance can develop across different types of opiates.

While cross dependence, cross addiction, and cross sensitization are terms that relate to substance use, they do not specifically address the tolerance aspect in the same way that cross tolerance does. Cross dependence refers to needing one substance to alleviate withdrawal symptoms of another, cross addiction deals with the potential for addiction to multiple substances, and cross sensitization involves increased sensitivity to a substance after exposure to another.