Evaluation of (R)-[11C]verapamil as PET tracer of P-glycoprotein function in the blood-brain barrier: kinetics and metabolism in the rat

Nucl Med Biol. 2005 Jan;32(1):87-93. doi: 10.1016/j.nucmedbio.2004.06.007.


There is evidence that P-glycoprotein (P-gp) in the blood-brain barrier (BBB) may be involved in the aetiology of neurological disorders. For quantification of P-gp function in vivo, (R)-[11C]verapamil can be used as a positron emission tomography (PET) tracer, provided that a mathematical model describing kinetics of uptake and clearance of verapamil is available. To develop and validate such a model, the kinetic profile and metabolism of (R)-[11C]verapamil have to be known. The aim of this study was to investigate the presence of labeled metabolites of [11C]verapamil in the plasma and (brain) tissue of Wistar rats. For this purpose, extraction and high-performance liquid chromatography (HPLC) methods were developed. The radioactive metabolites of (R)-[11C]verapamil in the liver were N-dealkylated compounds, O-demethylated compounds and a polar fraction formed from N-demethylation products of (R)-[11C]verapamil. Apart from this [11C] polar fraction, other radioactive metabolites of [11C]verapamil were not detected in the brain tissue. Thirty minutes after injection, unmetabolized (R)-[11C]verapamil accounted for 47% of radioactivity in the plasma and 69% in the brain. Sixty minutes after injection, unmetabolized (R)-[11C] verapamil was 27% and 48% in the plasma and the brain, respectively.

MeSH terms

  • ATP Binding Cassette Transporter, Subfamily B, Member 1 / metabolism*
  • Animals
  • Blood-Brain Barrier / diagnostic imaging*
  • Blood-Brain Barrier / metabolism*
  • Carbon Radioisotopes / pharmacokinetics
  • Drug Evaluation, Preclinical
  • Metabolic Clearance Rate
  • Organ Specificity
  • Positron-Emission Tomography / methods*
  • Radiopharmaceuticals / pharmacokinetics
  • Rats
  • Rats, Wistar
  • Tissue Distribution
  • Verapamil / pharmacokinetics*


  • ATP Binding Cassette Transporter, Subfamily B, Member 1
  • Carbon Radioisotopes
  • Radiopharmaceuticals
  • Verapamil