Fallypride is a high affinity dopamine D2/D3 receptor antagonist used in medical research, usually in the form of fallypride (18F) as a positron emission tomography (PET) radiotracer in human studies. Fallypride is a high affinity dopamine D2/D3 receptor antagonist used in medical research, usually in the form of fallypride (18F) as a positron emission tomography (PET) radiotracer in human studies.