Disposition of drugs in cystic fibrosis. VI. In vivo activity of cytochrome P450 isoforms involved in the metabolism of (R)-warfarin (including P450 3A4) is not enhanced in cystic fibrosis.

Abstract

OBJECTIVE:

To determine whether the activity of cytochrome P450 isoforms involved in the metabolism of (R)-warfarin is enhanced in cystic fibrosis.

DESIGN:

Six adult subjects with cystic fibrosis and six healthy control subjects, matched by age and sex, were administered (R)-warfarin as a single intravenous bolus dose (0.375 mg/kg), and urine and plasma samples were collected for 192 hours. The concentration of (R)-warfarin in plasma and the concentration of (R)-warfarin and its metabolites in urine were determined by HPLC and GC/MS, respectively. Plasma protein binding of (R)-warfarin was measured by ultrafiltration.

RESULTS:

The unbound plasma clearance of (R)-warfarin was not significantly (p > 0.05) different between the cystic fibrosis and the control groups (cystic fibrosis, 997 +/- 483 ml/hr/kg; control, 788 +/- 219 ml/hr/kg). The unbound metabolic clearances of (R)-warfarin to its oxidative metabolites--6-hydroxywarfarin, 7-hydroxywarfarin, 8-hydroxywarfarin, and 10-hydroxywarfarin (mediated by P450 3A4)--were also similar (p > 0.05) in the two groups (6-hydroxywarfarin: cystic fibrosis: 124.2 +/- 72.8 ml/hr/kg, control: 99.4 +/- 37.3 ml/hr/kg; 7-hydroxywarfarin: cystic fibrosis: 43.8 +/- 32.2 ml/hr/kg, control: 34.5 +/- 10.6 ml/hr/kg; 8-hydroxywarfarin: cystic fibrosis: 80.4 +/- 85.4 ml/hr/kg, control: 69.5 +/- 39.5 ml/hr/kg; 10-hydroxywarfarin: cystic fibrosis: 4.38 +/- 2.72 ml/hr/kg, control: 16.28 +/- 13.71 ml/hr/kg).

CONCLUSION:

The in vivo activity of cytochrome P450 isoforms involved in the metabolism of (R)-warfarin, including P450 3A4, is not enhanced in cystic fibrosis.

• Authors: J P Wang, J D Unadkat, S McNamara, T A O'Sullivan, A L Smith, W F Trager, B Ramsey
• Journal: Clinical pharmacology and therapeutics (Clin Pharmacol Ther) Vol. 55 Issue 5 Pg. 528-34 (May 1994) ISSN: 0009-9236 [Print] United States
• PMID: 8181197 (Publication Type: Journal Article, Research Support, U.S. Gov't, P.H.S.)

Chemical References

• Blood Proteins
• Warfarin
• Cytochrome P-450 Enzyme System

Topics

• Adult
• Blood Proteins (metabolism)
• Cystic Fibrosis (enzymology, metabolism)
• Cytochrome P-450 Enzyme System (metabolism)
• Female
• Humans
• Male
• Protein Binding
• Stereoisomerism
• Warfarin (metabolism, pharmacokinetics)