A patient who has developed opioid tolerance will experience which effect?

Choice A reason: Opioid tolerance does not reduce constipation; it may persist or worsen. Tolerance primarily reduces pain relief, so this is incorrect for the effect. Choice B reason: Respiratory depression risk may not increase with tolerance, as sensitivity to this effect also diminishes. Analgesia is most affected, so this is incorrect. Choice C reason: Euphoria typically decreases with tolerance, not increases, as receptor sensitivity drops. Reduced analgesia is the primary effect, so this is incorrect. Choice D reason: Opioid tolerance leads to decreased analgesic effect, requiring higher doses for pain relief. This is the hallmark of tolerance, making it the correct choice.