ABSTRACT:Absorption, metabolism, and excretion of paliperidone, an atypical antipsychotic, was studied in five healthy male subjects after a single dose of 1 mg of [ 14 C]paliperidone oral solution (ϳ16 Ci/ subject). One week after dosing, 88.4 to 93.8% (mean 91.1%) of the administered radioactivity was excreted: 77.1 to 87.1% (mean 79.6%) in urine and 6.8 to 14.4% (mean 11.4%) in the feces. Paliperidone was the major circulating compound (97% of the area under the plasma concentration-time curve at 24 h). No metabolites could be detected in plasma. Renal excretion was the major route of elimination with 59% of the dose excreted unchanged in urine. About half of the renal excretion occurred by active secretion. Unchanged drug was not detected in feces. Four metabolic pathways were identified as being involved in the elimination of paliperidone, each of which accounted for up to a maximum of 6.5% of the biotransformation of the total dose. Biotransformation of the drug occurred through oxidative N-dealkylation (formation of the acid metabolite M1), monohydroxylation of the alicyclic ring (M9), alcohol dehydrogenation (formation of the ketone metabolite M12), and benzisoxazole scission (formation of M11), the latter in combination with glucuronidation (M16) or alicyclic hydroxylation (M10). Unchanged drug, M1, M9, M12, and M16 were detected in urine; M10 and M11 were detected in feces. The monohydroxylated metabolite M9 was solely present in urine samples of extensive CYP2D6 metabolizers, whereas M10, another metabolite monohydroxylated at the alicyclic ring system, was present in feces of poor metabolizers as well. In conclusion, paliperidone is not metabolized extensively and is primarily renally excreted.

Human granulocyte chemotactic protein 2 (GCP-2) has originally been isolated from cytokine-stimulated osteosarcoma cells as a chemokine coproduced in minute amounts together with interleukin 8. Human GCP-2 (75 residues) was synthesized on a 0.25-mmol scale using Fmoc chemistry. After disulfide bridge formation and purification, monomeric GCP-2 was recovered as a 6-kDa protein; the pure synthetic protein showed a molecular mass of 8076 Da as determined by matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS). The exact amino acid sequence of synthetic GCP-2 was confirmed by Edman degradation. Synthetic GCP-2 was an equally active (minimal effective concentration of 1-3 nM) chemoattractant for neutrophilic granulocytes as was natural 75-residue GCP-2. At concentrations up to 30 nM, synthetic GCP-2 did not stimulate eosinophil, monocyte, or lymphocyte chemotaxis. GCP-2 induced a dose-dependent increase in [Ca2+]i in neutrophils, 1 nM being the minimal effective concentration. The GCP-2-induced [Ca2+]i increase was completely prevented by pertussis toxin. Prestimulation of neutrophils with equimolar concentrations of purified natural IL-8, GROalpha, GROgamma and ENA-78 abolished the [Ca2+]i increase in response to 1 nM GCP-2. Alternatively, the [Ca2+]i rise induced by these CXC chemokines was inhibited by pretreatment of neutrophils with GCP-2. GCP-2 stimulated [Ca2+]i increases in CXCR1- and CXCR2-transfected cells, demonstrating that GCP-2 binds to both IL-8 receptors. Intradermal injection of synthetic GCP-2 resulted in a dose-dependent neutrophil accumulation and plasma extravasation in rabbit skin. To provoke this skin reaction, GCP-2 (10 pmol/site) was nearly as effective as IL-8, indicating that it is an important complementary mediator of the inflammatory response.