Higher clearance of micafungin in neonates compared with adults: role of age-dependent micafungin serum binding.

Abstract

Micafungin, a new echinocandin antifungal agent, has been used widely for the treatment of various fungal infections in human populations. Micafungin is predominantly cleared by biliary excretion and it binds extensively to plasma proteins. Micafungin body weight-adjusted clearance is higher in neonates than in adults, but the mechanisms underlying this difference are not understood. Previous work had revealed the roles of sinusoidal uptake (Na(+) -taurocholate co-transporting peptide, NTCP; organic anion transporting polypeptide, OATP) as well as canalicular efflux (bile salt export pump, BSEP; breast cancer resistance protein, BCRP) transporters in micafungin hepatobiliary elimination. In the present study, the relative protein expression of hepatic transporters was compared between liver homogenates from neonates and adults. Also, the extent of micafungin binding to serum from neonates and adults was measured in vitro. The results indicate that relative expression levels of NTCP, OATP1B1/3, BSEP, BCRP and MRP3 were similar in neonates and in adults. However, the micafungin fraction unbound (f(u) ) in neonatal serum was about 8-fold higher than in the adult serum (0.033±0.012 versus 0.004±0.001, respectively). While there was no evidence for different intrinsic hepatobiliary clearance of micafungin between neonates and adults, our data suggest that age-dependent serum protein binding of micafungin is responsible for its higher clearance in neonates compared with adults.

• Authors: Souzan B Yanni, P Brian Smith, Daniel K Benjamin Jr, Patrick F Augustijns, Dhiren R Thakker, Pieter P Annaert
• Journal: Biopharmaceutics & drug disposition (Biopharm Drug Dispos) Vol. 32 Issue 4 Pg. 222-32 (May 2011) ISSN: 1099-081X [Electronic] England
• PMID: 21449041 (Publication Type: Comparative Study, Journal Article, Research Support, N.I.H., Extramural, Research Support, Non-U.S. Gov't)
• Copyright: Copyright © 2011 John Wiley & Sons, Ltd.

Chemical References

• Antifungal Agents
• Blood Proteins
• Echinocandins
• Lipopeptides
• Organic Anion Transporters
• Symporters
• Micafungin

Topics

• Adult
• Age Factors
• Antifungal Agents (blood, chemistry, pharmacokinetics, therapeutic use)
• Biliary Tract (physiology)
• Blood Proteins (metabolism)
• Echinocandins (blood, chemistry, pharmacokinetics, therapeutic use)
• Humans
• Infant, Newborn
• Lipopeptides (blood, chemistry, pharmacokinetics, therapeutic use)
• Liver (metabolism)
• Micafungin
• Organic Anion Transporters (metabolism)
• Protein Binding
• Symporters (drug effects, metabolism)