Pharmacokinetics of 1-(2-deoxy-2-fluoro-beta-L-arabinofuranosyl)-5-methyluracil (L-FMAU) in rats.

PURPOSE

The objective of this study was to characterize the pharmacokinetics of 1-(2-deoxy-2-fluoro-beta-L-arabinofuranosyl)-5-methyluracil (L-FMAU), a nucleoside analogue with potent activity against the hepatitis B virus and the Epstein-Barr virus, in rats.

METHODS

Three doses of L-FMAU were administered intravenously (10, 25, and 50 mg/kg) to rats, and L-FMAU concentrations in plasma and urine were measured by HPLC. Pharmacokinetic parameters were generated by using area-moment analysis.

RESULTS

There were no significant differences in the pharmacokinetic parameters between the three doses (alpha < 0.05). Thus, the disposition of L-FMAU was linear over the dosage of 10 to 50 mg/kg. Plasma concentrations of L-FMAU declined rapidly with a terminal phase half-life of 1.33 +/- 0.45 h (mean +/- SD). Total clearance of L-FMAU was moderate, averaging 1.15 +/- 0.28 L/h/kg. The fraction of compound excreted unchanged in urine was 0.59 +/- 0.13. No glucuronide metabolite was found in the urine. The steady-state volume of distribution was 1.12 +/- 0.26 L/kg indicating intracellular distribution of the compound. The fraction of L-FMAU bound to plasma proteins was approximately 15% and was independent of nucleoside concentration.

CONCLUSIONS

The pharmacokinetics of L-FMAU in rats were independent of dose over the dosage range of 10 to 50 mg/kg.