Which of the following is a characteristic of opioid analgesics?

Opioid analgesics are indeed derived from plant-based sources, such as opium poppy, which contains natural opiates like morphine and codeine. This characteristic highlights the origins of many opioid medications, as they have a longstanding history in both traditional and modern medicine. While synthetic versions of opioids exist, they often mimic the properties of these natural compounds.

The other choices do not accurately reflect the nature of opioid analgesics. They are typically used for moderate to severe pain rather than mild pain, are usually classified as controlled substances that require a prescription, and are recognized for their potential for abuse and addiction. Understanding the plant-based origin of opioids is essential for comprehending their pharmacological properties and the historical context of their use in pain management.