I read it back in the 80s so it must be older than 1985. The plot goes like this.
A doctor gets transferred to the future. He materialises in the middle of the road and almost gets killed. He finds out that medicine has been banned. The group that transported him finds him and tell him that they brought him to the future so that he may save the life of their leader. The leader has been stabbed to the heart with a dart, and frozen until they can find a doctor somewhere in time and bring him back to save the leader. But the leader's condition is irreversible and they decide to go back in time to the moment of the stabbing. But in a weird turn of events the doctor is forced to stab the leader.