Metabolism of CP-195,543, a leukotriene B4 receptor antagonist, in the Long-Evans rat and Cynomolgus monkey.

1. The fate of [14C]CP-195,543, a novel leukotriene B4 receptor antagonist, was studied following oral administration to the Long-Evans rat and Cynomolgus monkey. 2. Most of the radioactivity was primarily excreted in the faeces, and urine was a minor route of excretion. 3. CP-195,543 was extensively metabolized in the two species, primarily by two metabolic pathways: glucuronidation of unchanged CP-195,543 and oxidative metabolism, presumably by cytochrome P450. 4. The sites of glucuronidation were the carboxylic acid moiety and the hydroxy group. The ester glucuronide was the predominant glucuronide conjugate detected in the rat, whereas the monkey generated the ether as well as the ester glucuronide. 5. The structures of oxidative metabolites were elucidated using mass spectrometry (in the positive- and negative-ion mode) and 1H-NMR. The sites of hydroxylation were the benzylic group and the 3-position of the benzopyran ring. 6. This study has indicated that CP-195,543 was mainly eliminated by Phase II metabolism in both species.

Characterization of polar urinary metabolites by ionspray tandem mass spectrometry following dansylation.

The present report illustrates the application of dansyl chloride coupled with ion spray tandem mass spectrometry (IS-MS/MS) in identifying polar urinary metabolites. In the course of the metabolism studies of a drug that is currently in development, the urine from rats and dogs was collected following oral administration of radiolabelled compound. Urinary metabolic profiles of the rat and dog indicated the presence of four major peaks and one major peak, respectively, in the radiochromatogram. Since all attempts to identify the peaks by conventional MS/MS techniques failed, the metabolites were isolated by fraction collection and dansylated. Derivatization of the metabolites resulted in the formation of more hydrophobic, readily ionizable species which were more sensitive in IS-MS/MS analysis than the underivatized metabolites. Examination of the molecular ions and the product ion mass spectra of these derivatives revealed the structures of all the urinary metabolites. The metabolites in the rat and the dog were 4-hydroxyphenylpiperazine glucuronide (M1), 1,4-dihydroxyphenyl glucuronide (M2), 1,4-dihydroxyphenyl sulfate (M3) and phenylpiperazine (M4). Thus, derivatization with dansyl chloride in conjunction with tandem mass spectrometry is a useful tool in identifying polar urinary metabolites.

Metabolism of droloxifene in the CD-1 mouse, Fischer-344 rat and cynomolgus monkey.

1. The fate of [14C]droloxifene, a novel non-steroidal anti-oestrogen, was studied following oral administration to the CD-1 mouse, F-344 rat and Cynomolgus monkey. 2. Most of the radioactivity was primarily excreted in the faeces and urine was the minor route of excretion. 3. Droloxifene was extensively metabolized in all three species, primarily by two metabolic pathways; glucuronidation of unchanged droloxifene and oxidative metabolism, presumably by cytochrome P450. 4. In mouse, oxidative metabolism followed by conjugation played a significant role in the elimination of droloxifene. An unusual diglucuronide of 4-hydroxydroloxifene was also identified in this species. 5. In rat, glucuronidation and oxidative metabolism were significant, whereas in monkey glucuronidation of droloxifene was the predominant pathway of elimination.

Pharmacokinetics and metabolism of single oral doses of trovafloxacin.

Trovafloxacin, a new fluoronaphthyridone derivative related to fluoroquinolone antimicrobial drugs, has demonstrated the following characteristics: significant gram-positive and gram-negative activity; significant activity against anaerobes and atypical respiratory pathogens; approximately 11-hour elimination half-life, permitting once-daily administration; and good tissue penetration. Because <10% of an orally administered dose is recovered in urine as unchanged drug, the predominant route of trovafloxacin elimination appears to be nonrenal. The two studies described in this review examined the metabolism and excretion of trovafloxacin and compared the time course and concentrations of trovafloxacin and its metabolites in bile to those in serum. In the first study, four healthy male volunteers received a single, oral 200-mg dose of radiolabeled trovafloxacin. In the second study, three patients with indwelling nasobiliary tubes received a single 200-mg dose of trovafloxacin. Samples of blood, urine, bile, and feces were collected. Trovafloxacin in urine and serum was analyzed by high-performance liquid chromatography (HPLC) with ultraviolet (UV) detection and in bile by HPLC-mass spectroscopy (MS). Levels of the N-acetyl metabolite in bile were determined by HPLC/UV/MS. Metabolites in serum, urine, and feces were determined by reverse-phase HPLC/MS, and radioactivity in these samples was assayed by liquid scintillation counting. In the first study, 63.3% and 23.1% of total radioactivity were recovered in feces and urine, respectively, with most of the radioactivity in urine in the form of the ester glucuronide metabolite (12.8%) and unchanged trovafloxacin (5.9%). Unchanged drug, the N-acetyl metabolite, and the N-sulfate of trovafloxacin accounted for 43.2%, 9.2%, and 3.9%, respectively, of the radioactivity in feces. In the second study, biliary trovafloxacin concentrations were highest between 1.5 and 10 hours postdose, and the maximum concentrations ranged from 18.9 to 37.9 microg/mL. The mean bile:serum ratio of trovafloxacin was 14.9, and the biliary concentration of parent drug was higher than that of its N-acetyl metabolite. In both studies, trovafloxacin was well tolerated, with no discontinuations due to adverse events. The pharmacokinetic profile of trovafloxacin in serum was consistent in healthy subjects and in individuals who had undergone recent hepatobiliary surgery. Trovafloxacin is metabolized primarily by the liver, through phase II metabolism (glucuronidation 13.2%, N-acetylation 10.4%, and N-sulfoconjugation 4.1%); minimal oxidative metabolism was detected. Renal elimination accounted for <10% of the administered dose. The high bile to serum ratio and higher trovafloxacin concentrations relative to metabolite concentrations are consistent with nonrenal elimination. These pharmacokinetic and pharmacodynamic results, together with a broad antimicrobial spectrum, long 11-hour elimination half-life, and low drug-interaction potential, suggest that trovafloxacin may be particularly appropriate for use in the surgical setting.

Excretion and metabolism of trovafloxacin in humans.

The metabolism and excretion of trovafloxacin was investigated in four healthy male volunteers after a single oral administration of 200 mg of [14C]trovafloxacin (118 microCi). Mean values of 23.1 and 63.3% of the administered dose were recovered in the urine and feces, respectively, after 240 hr. The Cmax of total radioactivity and unchanged trovafloxacin in serum was 3.2 micrograms-equiv/ml and 2.9 micrograms/ml, respectively, and peaked in 1.4 hr. The mean AUC0-infinity for radioactivity and trovafloxacin was 58.2 micrograms-eq.hr/ml and 32.2 micrograms.hr/ml, respectively. This implied that unchanged trovafloxacin constituted 55% of the circulating radioactivity. Urine and fecal samples were analyzed by LC/MS/MS for characterization of the metabolites, and the quantity of each metabolite in the matrices was assessed by means of a radioactivity detector. The profile of radioactivity in urine showed three main metabolites that were identified as the trovafloxacin glucuronide (M1), N-acetyltrovafloxacin glucuronide (M2), and N-acetyltrovafloxacin (M3). The major fecal metabolites were M3 and the sulfate conjugate of trovafloxacin (M4). Analysis of circulating metabolites from pooled serum extracts obtained at 1, 5, and 12 hr indicated that M1 was the major circulating metabolite (22% of circulating radioactivity), whereas M2 and M3 were detected in minor amounts. The results of the present study revealed that oxidative metabolism did not play a significant role in the elimination of trovafloxacin, and phase II conjugation was the primary route of trovafloxacin clearance in humans.

Metabolism and excretion of trovafloxacin, a new quinolone antibiotic, in Sprague-Dawley rats and beagle dogs. Effect of bile duct cannulation on excretion pathways.

The excretion and metabolism of trovafloxacin was investigated after administration of a single oral dose of [14C]trovafloxacin to Sprague-Dawley rats and beagle dogs. The bile was the major route of excretion in rats (59% of the dose). Trovafloxacin was extensively metabolized in this species, and only 3% of the dose was excreted unchanged. Glucuronidation and acetylation were the major metabolic pathways involved in the elimination, and no oxidative metabolites were detected in rats. In dogs, 97.6 and 2.7% of the dose was recovered in feces and urine, respectively, in 72 hr. However, excretion studies in bile duct-cannulated dogs revealed that 28.2% of the radioactivity was recovered in bile, whereas 45.6% was in urine. This suggested that bile duct cannulation had affected the disposition of trovafloxacin. Analysis of bile and urine of bile duct-cannulated dogs by LC/MS/MS indicated that glucuronidation was the major metabolic pathway in dogs as well. Two novel metabolites were identified in the bile of this species. One was confirmed as a pyrroline analog of trovafloxacin (M7), and the second was tentatively identified as the hydroxycarboxylic acid analog (M6). The differences in metabolism of trovafloxacin in the bile duct-cannulated and noncannulated dogs were investigated by comparison of the metabolite profiles in urine and feces of these animals. Although the metabolites in urine were similar, the extracts of fecal samples obtained from noncannulated animals revealed the presence of N-acetyltrovafloxacin (M3). Incubation of trovafloxacin with cecal contents of dogs under anaerobic conditions suggested the involvement of intestinal microflora in the formation of this metabolite. Metabolite M3 was absent from fecal extracts of bile duct-cannulated dogs, suggesting that surgery had affected the metabolism of trovafloxacin by gut microflora.