Pope Benedict told Catholic pharmacists on Monday (29 Oct) they should have the right to refuse supplying drugs that cause abortion or euthanasia.
The pope, addressing an international conference of Catholic pharmacists in Vatican City, said refusal to sell certain drugs was a form of conscientious objection.
The profession was a key intermediary between doctors and patients, the pope claimed, and pharmacists should also tell customers about the implications of buying drugs.
The pontiff said: "It is not possible to anaesthetize the conscience, for example, when it comes to molecules whose aim is to stop an embryo implanting or to cut short someone's life.
"I invite your federation to consider conscientious objection which is a right that must be recognized for your profession so you can avoid collaborating, directly or indirectly, in the supply of products which have clearly immoral aims, for example abortion or euthanasia."
One drug the pope was clearly referring to is the 'morning after' pill, which prevents fertilised eggs embedding in a woman's uterus.
The Vatican has previously spoken out against Italian politicians who advocate use of the pill.