Euthanasia and physicians' moral duties

Opponents of euthanasia sometimes argue that it is incompatible with the purpose of medicine, since physicians have an unconditional duty never to intentionally cause death. But it is not clear how such a duty could ever actually be unconditional, if due consideration is given to the moral weight of countervailing duties equally fundamental to medicine. Whether physicians' moral duties are understood as correlative with patients' moral rights or construed noncorrelatively, a doctor's obligation to abstain from intentional killing cannot be more than a defeasible duty.