From the Hippocratic Oath:

"I will apply dietetic measures for the benefit of the sick according to my ability and judgment; I will keep them from harm and injustice. (How many docs do you know that prescribe dietary measures before prescribing poison?)

I will neither give a deadly drug to anybody if asked for it, nor will I make a suggestion to this effect. Similarly I will not give to a woman an abortive remedy. In purity and holiness I will guard my life and my art.