The active substance in Striascan, ioflupane (123I), is a radiopharmaceutical. It contains a substance called ioflupane, which is labelled with 123I (iodine 123), a radioactive form of iodine. Ioflupane attaches specifically to structures on nerve cell endings that are responsible for the transport of dopamine.

When Striascan is injected, ioflupane (123I) is distributed by the blood and builds up in the striatum, where it attaches to the structures that transport dopamine. This build-up can be seen using an imaging technique called single-photon-emission computed tomography (SPECT), which detects the radioactive iodine 123.

In patients with Parkinson’s disease and related diseases, and in patients with dementia with Lewy bodies, there is typically a loss of the dopamine-containing nerve cells in the striatum. If this happens, the amount of Striascan attaching to these nerve cells is greatly reduced, which can be seen on the scan. This enables diseases related to Parkinson’s disease to be distinguished from essential tremor, and for Lewy body dementia to be distinguished from Alzheimer’s disease.