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Metabolic site of propofol
- Daisuke Takizawa (25 February 2009)
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Daisuke Takizawa
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Metabolic site of propofol Daisuke Takizawa, MD 1) Eri Takizawa, MD 1) Haruhiko Hiraoka, MD 2) Katsunori Nakamura, PhD 3), Koujirou Yamamoto, PhD 3) 1) Department of Anesthesiology, Takasaki medical Office, 34-2-1108, Asahi-machi, Takasaki City 370-0052, Japan. 2) Department of Anesthesiology, Takasaki Anesthesia Clinic 3) Department of Clinical Pharmacology, Gunma University, School of Medicine Correspondence should be addressed to: Daisuke Takizawa, MD Department of Anesthesiology, Takasaki Medical Office, 34-2-1108, Asahi- machi, Takasaki City 370-0052, Japan. E-mail: d-takiza@bf6.so-net.ne.jp Takata et al reported that there was no significant difference in propofol concentration between femoral arterial and renal venous blood in a swine model 1). They concluded that the kidney is a minor site of propofol elimination in a swine model 1). In contrast to the results of their study, we previously reported that the renal extraction ratio of propofol was 50-70 % in humans 2). Takata et al suggested the possibility that the blood sample from the renal vein was contaminated with blood from the inferior vena cava in our study. As Takata et al pointed out, it can not be denied the possibility of contamination with blood from the inferior vena cava in our study. We performed the study with a continuous infusion method and corrected the blood samples in almost steady state. This point accords with Takata’s study. At steady state, propofol concentrations are equal in any blood vessels except the blood vessels from the metabolic site. Therefore, if the blood sample from the renal vein was contaminated with blood from the inferior vena cava, the renal extraction ratio was underestimated. The method of Takata’s study was controlled very well and the possibility of contamination with blood from the inferior vena cava was successfully avoided. Therefore, it is considered that the kidneys are only a minor contributor to extrahepatic elimination of propofol in swine. Concerning with the point which internal organs have a enzymes for metabolism 3)4, animal studies have less importance in the investigation of which organs contribute to extrahepatic clearance in humans. References 1) Tatata K, Kurita T, Morishita Y, Morita K, Uraoka M, Sato S. Do the kidneys contribute to propofol elimination? Br J Anaeth 2008; 101: 648-52 2) Takizawa D, Hiraoka H, Goto F, Yamamoto K, Horiuchi R. Human kidneys play an important role in the elimination of propofol. Anestheiology 2005;102:327-30 3) Court MH, Greenblatt DJ. Biochemical basis for deficient paracetamol glucuronidation in cats: an interspecies comparison of enzyme constraint in liver microsomes. J Pharm Pharmacol. 1997;49:446-9. 4) Hansen KT, Stentoft K. Characterization of benzazepine UDP-glucuronosyl -transferases in laboratory animals and man. Xenobiotica. 1995;25:611-22. Conflict of Interest:None declared |
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