Regional P-glycoprotein activity and inhibition at the human blood-brain barrier as imaged by positron emission tomography

S. Eyal, B. Ke, M. Muzi, J. M. Link, D. A. Mankoff, A. C. Collier, J. D. Unadkat

Research output: Contribution to journalArticle

50 Scopus citations


We used positron emission tomography (PET) to evaluate the contribution of P-glycoprotein (P-gp), present at the human blood-brain barrier (BBB), to regional drug distribution in the brain. Eleven healthy volunteers underwent PET imaging with 11 C-verapamil before and during cyclosporine A infusion. Regional P-gp inhibition was expressed as cyclosporine A-induced percentage change in the distributional clearance of verapamil (K 1) in the brain, normalized to the regional blood flow (rCBF). K 1 estimates were similar across gray-matter regions of the brain and lower in the white matter regions, but all these estimates were considerably lower than rCBF. Normalization of K 1 by rCBF diminished the differences in estimates related to gray matter and white matter. In contrast, the K 1 for the pituitary, which is situated outside the BBB, approximated the rCBF. The magnitude of P-gp inhibition was comparable across BBB-protected brain structures. Our results indicate that P-gp and its inhibition equally affect the distribution of drugs (and therefore their neuro-efficacy and toxicity) in the various brain regions protected by the BBB.

Original languageEnglish (US)
Pages (from-to)579-585
Number of pages7
JournalClinical pharmacology and therapeutics
Issue number5
StatePublished - May 1 2010


ASJC Scopus subject areas

  • Pharmacology
  • Pharmacology (medical)

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