Physicians are permitted to prescribe drugs off-label. By off-label, I really mean “silent label.” Silent label implies the manufacturer has not received FA approval to market the drug as safe and effective for treating the off-label condition.
An example: some antibiotics have been approved for those 18 or older. The label granted by the FDA likely reflects the submission. The manufacturer might have wanted to keep costs down and only test adults. Most manufacturers know that if a drug is approved for adults, some physicians will prescribe the medication for younger patients. And the law generally allows physicians to do precisely that. (We are aware of only a narrow class of restrictions where the federal government dictates the uses for which a drug can be prescribed – anabolic steroids and human growth hormone). Eventually, the literature will accumulate data about the safety and efficacy of the antibiotic’s use in minors.
So doctors have had significant latitude to prescribe medications off-label.