I have a family member in the medical field, and I've asked them about this before. For the most part, any medications and drug can cause harm to a child. Sometimes hospitals will give the smallest dose of morphine to patients under 12, or light forms of aspirin. I've never heard of parents refusing a doctor recommendation, but I could see where it might happen. I was given morphine as a kid when they stitched my knee, so I think it probably doesn't harm kids completely.