The male genital tract is not a pharmacological sanctuary from efavirenz

L. B. Avery, R. P. Bakshi, Y. J. Cao, C. W. Hendrix

Research output: Contribution to journalArticlepeer-review

18 Scopus citations


Many antiretroviral (ARV) drugs have large blood plasma-to-seminal plasma (BP/SP) concentration ratios. Concern exists that these drugs do not adequately penetrate the male genital tract (MGT), resulting in the MGT becoming a pharmacological sanctuary from these agents, with ineffective MGT concentrations despite effective blood concentrations. Efavirenz (EFV) is the most highly protein-bound ARV drug, with 99% binding in blood plasma and the largest BP/SP total EFV concentration ratio, reportedly ranging from 11 to 33. To evaluate protein binding as an explanation for the differences between the drug concentrations in blood and semen, we developed a novel ultrafiltration method, corrected for the duration of centrifugation, to measure protein binding in the two matrices. In six subjects, protein-free EFV concentrations were the same in blood and semen; the median (interquartile range (IQR)) protein-free EFV SP/BP ratio was 1.21 (0.99-1.35); EFV protein binding was 99.82% (99.79-99.86) in BP and 95.26% (93.24-96.67) in SP. This shows that the MGT is not a sanctuary from EFV.

Original languageEnglish (US)
Pages (from-to)151-156
Number of pages6
JournalClinical pharmacology and therapeutics
Issue number1
StatePublished - Jul 2011

ASJC Scopus subject areas

  • Pharmacology
  • Pharmacology (medical)


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