Overcoming the obstacle of excess acetonitrile content in the final fluorine-18 radiotracers

Acetonitrile is widely used as a solvent in synthesizing various fluorine-18 positron emission tomography (PET) radiotracers. Acetonitrile is classified as a Class II residual solvent, and due to its inherent toxic properties, the quantity of residual acetonitrile in drug products has to be limited. When working under Good Manufacturing Practices (GMP) during the radiosynthesis of a radiotracer, the aim is to control all solvent concentrations contained in the ready-to-use product. All products must meet predetermined specifications. Rarely, these limits may be exceeded. To avoid eliminating the entire batch, applying a straightforward time-based technique would be desirable to allow the majority of the product to be safely used. This technique should be based on determining a specific time and volume for which the radiotracer can be utilized in the patients after completing quality control analysis. Here, we report a very simple Excel sheet program based on existing mathematical equations that calculates the exact time and volume at which the radiotracer product can be safely administered to a patient.