The synthesis of [O-methyl-¹¹C]venlafaxine: A non-classical, fast-acting antidepressant

As part of our program to develop PET tracers for the 5-HT reuptake site, venlafaxine, a non-classical, fast-acting antidepressant, was selected as a candidate for labelling with ¹¹C for in vivo evaluation. [O-methyl-¹¹C]venlafaxine was produced by the alkylation of O-desmethyl venlafaxine with [¹¹C]methyl iodide followed by HPLC purification and formulation. Radiochemically pure [O-methyl-¹¹C]venlafaxine was obtained in a 30 ± 5 % decay corrected radiochemical yield and a specific activity > 50 GBq/μmol (1.4 Ci/μmol) at the end of synthesis. For a typical production starting with 46 GBq (1.3 Ci) [¹¹C]CO₂, 5.2 GBq (140 mCi) [O-methyl-¹¹C]venlafaxine was obtained as a sterile, formulated solution in a synthesis time of 30 min (counted from EOB).