Synthesis of n.c.a. carbon-11 labelled clozapine and its major metabolite clozapine-N-oxide and comparison of their biodistribution in mice

Nucl Med Biol. 1994 Oct;21(7):921-5. doi: 10.1016/0969-8051(94)90080-9.


N.c.a. [11C]clozapine, [8-chloro-11-(4-[methyl-11C]-methyl-1-piperazinyl)-5H-dibenzo[b,e]-1, 4-diazepine], 1, an atypical neuroleptic was synthesized by N-methylation of the desmethyl compound norclozapine, 3, using [11C]methyl iodide or [11C]methyl triflate for comparison. Subsequent oxidation of 1 with m-chloroperoxybenzoic acid yielded clozapine-N-oxide, 2, the major metabolite of 1. Purification of both radiolabelled products was carried out using a combined semi-preparative HPLC/solid phase extraction procedure. In preparative scale runs overall radiochemical yields for 1 and 2 were 70 and 65%, respectively. The radiochemical purities of both compounds exceeded 98% and the specific activities were in the range of 92-130 GBq/mumol (2.5-3.5 Ci/mumol). Biodistribution of 1 and 2 has been studied in NMRI mice. 10 min p.i. clozapine shows a 24-fold higher brain uptake than its major metabolite. At 60 min p.i., however, the cerebral uptake of both compounds is almost identical.

Publication types

  • Comparative Study

MeSH terms

  • Animals
  • Brain / metabolism
  • Carbon Radioisotopes / pharmacokinetics
  • Chromatography, High Pressure Liquid
  • Clozapine / analogs & derivatives*
  • Clozapine / chemical synthesis*
  • Clozapine / pharmacokinetics
  • Female
  • Kidney / metabolism
  • Liver / metabolism
  • Mice
  • Myocardium / metabolism
  • Tissue Distribution


  • Carbon Radioisotopes
  • Clozapine
  • clozapine N-oxide