The synthesis of no-carrier-added and carrier-added 18F-labelled haloperidol

Fluorine-18 labelled haloperidol (18F-HP) was synthesized by a fluorine-fluorine exchange reaction on haloperidol, fluorine-chlorine exchange on a chloro-analog of haloperidol, and from 18F-labelled p-fluorobenzonitrile prepared by two different exchange reactions. Nucleophilic fluorine was used in the form of tetra n-butylammonium fluoride. The overall radiochemical yield, expressed at the end of syntheses was 5% for exchange in haloperidol and about 2%-3% for exchange in chloroanalog in a 40 min synthesis (from the end of the irradiation). Specific activities up to 1 Ci/mmol for haloperidol and up to 5000 Ci/mmol for chloro-analog as substrates were obtained. The syntheses using p-substituted chloro-and nitro-benzonitriles as starting materials for the exchange reaction gave a product with an average specific activity of about 2000 Ci/mmol and in general an overall radiochemical yield of 5%-10%. Purification of [18F]haloperidol was done by HPLC on a C-18 column. The radiochemical purity as assessed by thin layer radiochromatography (TLRC) of the final product was at least 95%, with high chemical purity. (author)