Clinical trials were first introduced in Avicenna 's The Canon of Medicine in 1025 AD , where he laid down rules for the experimental use and testing of drugs . He wrote a precise guide for practical experimentation in the process of discovering and proving the effectiveness of medical drugs and substances . In The Canon of Medicine in 1025 AD , he laid down rules for the experimental use and testing of drugs and wrote a precise guide for practical experimentation in the process of discovering and proving the effectiveness of medical drugs and substances .