Hepatic metabolism of the new antipsychotic agent, mazapertine, in rat--API-MS/MS identification of metabolites

Metabolic fate of the antipsychotic agent, mazapertine, in man--API-MS and MS/MS identification of urinary metabolites

The in vivo metabolism of the antipsychotic agent mazapertine was studied after oral administration of mazapertine succinate (40 mg/subject) to two healthy volunteers, and urine (0-24 hours) was obtained for metabolite identification using API-ionspray LC/MS and MS/MS analysis. Unchanged mazapertine (12% of the sample) plus 10 metabolites were profiled, quantified, and tentatively identified on the basis of MS data, Glusulase-hydrolysis, and by comparison to synthetic samples. The formation of mazapertine metabolites are via seven metabolic pathways: (1) phenylhydroxylation, (2) piperidyl oxidation, (3) O-dealkylation, (4) N-dephenylation, (5) oxidative N-debenzylation, (6). depiperidylation, and (7) glucuronidation. Pathways 1, 2, 5 and 7 formed 4-OH-phenyl-mazapertine (M1, 18%) and 4-OH-piperidyl (M2, 14%)-mazapertine, carboxybenzoylpiperidine (M8, 10%) and its glucuronide (M9, 14%) as four major metabolites. Six moderate and minor metabolites (M3-M7 & M10; each < or =10%) formed via a combination of pathways 1-6. Mazapertine is extensively metabolized in humans.

Hepatic metabolism of two alpha-1A-adrenergic receptor antagonists, phthalimide-phenylpiperazine analogs (RWJ-69205 and RWJ-69471), in the rat, dog and human

The In vitro metabolism of two alpha-1A-adrenergic antagonists, RWJ-69205 and RWJ-69471 (phthalimide-phenylpiperazine analogs), was assessed after 30 and 60 min incubations with rat, dog and human hepatic S9 fractions in the presence of an NADPH-generating system. Unchanged RWJ-69205 (> or = 72% of the sample in all species) plus 3 metabolites from the RWJ-69205 incubations, and unchanged RWJ-69471 (> or = 60% of the sample in all species) and 7 metabolites from the RWJ-69471 incubations, were profiled, quantified, and tentatively identified on the basis of API-MS and MS/MS data. The formation of RWJ-69205 and RWJ-69471 metabolites are via the following five metabolic pathways: 1. phenylhydroxylation, 2. O-dealkylation, 3. oxidative N-dealkylation, 4. N-dephenylation, and 5. dehydration. Pathway 1 formed 2 major/moderate hydroxy-phenyl metabolites of 2 analogs (4-17%) in all species, and pathway 2 produced 2 O-desisopropyl metabolites of 2 analogs in major/moderate (7-16%) in rat and human, and in trace (< 1%) in dog; in conjunction with pathway 1, yielded a minor diphenolic metabolite (< 1-2%) in RWJ-69471. Pathway 3 formed a minor N-dealkylated metabolite, isopropoxyphenyl piperazine (< 1-6%) in all species of 2 analogs. Pathways 4 and 5 produced 2 minor N-desphenyl metabolite and dehydrated metabolite, respectively, in rat and human S9 (< or = 1-2%) in RWJ-69471. Both RWJ-69205 and RWJ-69471 were less extensively metabolized in the dog. However, rat and human appeared to metabolize RWJ-69471 more extensively than RWJ-69205 in this hepatic system.

Distribution and metabolism of the antipsychotic agent mazapertine succinate in rats

The pharmacokinetics and drug disposition of 14C 1-[3-[[4-[2-(1-methylethoxy)phenyl]-1-piperazinyl]methyl]benzoy]piperidine succinate (RWJ-37796, mazapertine, Mz) have been investigated in male and female Sprague-Dawley rats. Approximately 93% of the orally administered radioactive dose (30 mg/kg) was recovered after 7 days. Fecal elimination accounted for approximately 63% of the dose while urine accounted for 30%. The rate of elimination of 14C Mz was rapid with 81% of the total fecal and 94% of the total urinary radioactivity being excreted within 24 h. There were no significant gender differences in the overall excretion pattern. The maximal plasma concentration of Mz and total radioactivity occurred at 0.5h after dosing and plasma concentrations were consistently higher in female rats. The Mz concentration declined rapidly in plasma with a terminal half-life<2 h. The total radioactive dose in plasma displayed a considerably longer terminal half-life of 9-13 h. Mz and a total of 15 metabolites were isolated and identified in these samples. Unchanged Mz accounted for <5% of the radioactive dose in excreta samples and <8% of the sample in plasma (0-24 h). Metabolites were formed by phenyl hydroxylation, piperidyl oxidation, O-dealkylation, N-dephenylation, oxidative N-debenzylation and glucuronide conjugation.

Metabolism of the alpha-1A-adrenergic receptor antagonist, pyridine-phenylpiperazine analog (RWJ-69597), in rat, dog and human hepatic S9 fractions -API-MS/MS identification of metabolites

The In vitro metabolism of the alpha-1A-adrenergic antagonist, RWJ-69597, an analog of pyridine-phenylpiperazines, was conducted after incubation with rat, dog and human hepatic S9 fractions in the presence of an NADPH-generating system. Unchanged RWJ-69597 (> or =43% of the sample in all species) plus 9 metabolites were profiled, quantified, and tentatively identified on the basis of API-MS and MS/MS data. The four metabolic pathways for the formation of RWJ-69597 metabolites are: 1. methyl/phenyl/piperazinylhydroxylation, 2. N/Odealkylation, 3. N-dephenylation, and 4. dehydration. Pathway 1 formed 1 major (8-36%) and 3 minor (<1-3%) hydroxylated metabolites. Pathway 2 produced 2 moderate/minor N/O-dealkylated metabolites (<1- < or =11%), and in conjunction with pathway 1, formed 1 minor diol metabolites (< or =2%). Pathways 3 and 4 generated 2 minor metabolites, N-desphenyl RWJ-69597 (< or =4%) and dehydrated RWJ-69597 (< or =2%), respectively. RWJ-69597 is more extensively metabolized in the rat than the dog or the human in this hepatic system.

Metabolism of the new α-1A-adrenergic receptor antagonist, phthalimide-phenylpiperazine analog (RWJ-69442), in rat, dog and human hepatic S9 fractions, and in rats

The in vitro and in vivo metabolism of RWJ-69442, an alpha-1A-adrenergic receptor antagonist, was investigated after incubation with rat, dog, and human hepatic S9 fractions in the presence of NADPH-generating system, and a single oral/iv dose administration to rats (oral: 100 mg/kg; iv: 10 mg/kg). Unchanged RWJ-69442 (> or =30% of the sample in vitro; < or =47% of the sample in vivo) plus 14 metabolites were profiled, quantified and tentatively identified on the basis of API-MS and MS/MS data. The metabolic pathways for RWJ-69442 are proposed via the 4 steps: 1. phenyl/piperazinylhydroxylation, 2. N/O-dealkylation, 3. N-dephenylation, and 4. dehydration. Pathway 1 formed OH-phenyl-RWJ-69442 (M1, 4-32% in vitro & in vivo), and diOH-RWJ-69442 (M4, <1-4% in vitro & in vivo). Pathway 2 generated O-desisopropyl-RWJ-69442 (M2, <1-21% in vitro & in vivo), N-desmethyl-RWJ-69442 (M3, 2-3% in vitro & in vivo), N-desmethyl-M2 (M6, 1-8% in vitro & in vivo), and N-dealkylated RWJ-69442 (M9, < or =1-17% in vitro & in vivo), and in conjunction with pathway 1 produced 6 minor to major oxidized metabolites, OH-M2 (M5, 1-2% in vitro), OH-M3 (M11, 4-6% in vivo), OH-M9 (M10, <1-34% in vitro & in vivo), O-desisopropyl-M9 (M12, 3-21% in vivo), O-desisopropyl-M10 (M13,2-12% in vivo), and dehydro-M13 (M14, 25% in vivo). Pathways 3 and 4 formed 2 minor metabolites, N-desphenyl-RWJ-69442 (M7, <1-12% in vitro & in vivo) and dehydrated-RWJ-69442 (M8, <1-2% in vitro), respectively. RWJ-69442 is extensively metabolized in vitro in the rat and human (except dog), and in vivo in the rat.