The practice of medicine is mostly driven by research. Nearly every medical remedy you know of started as a hypothesis, which was eventually supported by research. There tends to be a long road spanning from animal-based research, eventually feeding into humans. Real-life medical experiments are almost inevitable, requiring a select group of patients to avail themselves of medical research.
In your day-to-day medical encounters, you may be requested to participate in some clinical experiments. Some people will feel compelled to decline, possibly thinking about the risks involved. However there are many safety processes in place to protect you as a participant.