Metabolism is an important route of pentamidine elimination in the rat: disposition of 14C-pentamidine and identification of metabolites in urine using liquid chromatography-tandem mass spectrometry

Pharmacol Toxicol. 1995 Aug;77(2):114-20. doi: 10.1111/j.1600-0773.1995.tb00999.x.


This study assesses the contribution of metabolism for the disposition of pentamidine in the rat. With the use of 14C-labelled compound, the excretion of radioactivity in urine and faeces has been studied in four rats during 44 days after a single intravenous injection of the drug. The urinary and faecal excretion of the radioactivity were of equal importance; 22 +/- 2% (mean +/- S.D.) and 25 +/- 4% being detected in urine and faeces, respectively. The activity in organs and tissues at 44 days after drug administration was also measured and amounted to 21 +/- 5% of the administered dose. Using HPLC the proportion of metabolites in urine in relation to unchanged pentamidine increased with time after dose, being 76 +/- 15% (mean +/- S.D.) of the total excreted radioactivity on day 1 and 97 +/- 1% on day 6. HPLC--tandem mass spectometry was used for identification of metabolites in urine obtained from four rats given unlabelled pentamidine. Using synthetic reference compounds and the selective MS/MS mode four oxidized metabolites of pentamidine were identified either by direct injection into the system or by analyses of extracted urine. Thus, a substantial part of pentamidine is excreted as metabolites in urine.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Animals
  • Carbon Radioisotopes
  • Chromatography, High Pressure Liquid
  • Feces / chemistry*
  • Male
  • Mass Spectrometry
  • Molecular Weight
  • Pentamidine / metabolism
  • Pentamidine / urine*
  • Rats
  • Rats, Sprague-Dawley
  • Tissue Distribution


  • Carbon Radioisotopes
  • Pentamidine