It is unconstitutional--and unethical--for physicians to participate in evidence-gathering against pregnant women suspected of being addicted to illegal substances without informing them of their constitutional rights or gaining their informed consent.
Physicians have a responsibility to assess elderly patients for conditions that could affect their ability to drive safely and to be familiar with state laws that govern physician duty to report impaired drivers.
When patients request drugs for nonmedical reasons, the most effective intervention may be to explore with the patient his or her reasons for using drugs to make lifestyle changes.