RESUMEN
Using pig kidney epithelial cells (LLC-PK1), the present study assesses the cyclic GMP stimulatory effect of pentaerithrityl tetranitrate and its metabolites in comparison to other therapeutically used nitric oxide donors. Pentaerithrityl tetranitrate was found to be the most potent activator of cyclic GMP synthesis compared to other clinically relevant organic nitrates (glyceryl trinitrate, isosorbide dinitrate, isosorbide-5-mononitrate). The phase I metabolite pentaerithrityl trinitrate was equipotent with its parent compound in stimulating cyclic GMP. The concentration-response curves of pentaerithrityl dinitrate and isosorbide dinitrate for cyclic GMP accumulation were virtually identical. In contrast, pentaerithrityl mononitrate and the phase II metabolite pentaerithrityl trinitrate glucuronide did not alter basal cyclic GMP levels. It is concluded that the long-term vasodilatory and antiischemic effects of pentaerithrityl tetranitrate are caused to a substantial extent by cyclic GMP-mediated actions of its pharmacologically active phase I metabolites.
Asunto(s)
GMP Cíclico/biosíntesis , Tetranitrato de Eritritilo/análogos & derivados , Guanilato Ciclasa/metabolismo , Donantes de Óxido Nítrico/farmacología , Animales , Células Cultivadas , Activación Enzimática , Células Epiteliales/citología , Dinitrato de Isosorbide/farmacología , Riñón/citología , PorcinosRESUMEN
Up to now, there has been no data available on the pharmacokinetics of pentaerythrityl tetranitrate (PETN, CAS 78-11-5) and its metabolites, pentaerythrityl-trinitrate (PE-tri-N), pentaerythrityl-dinitrate (PE-di-N), pentaerythrityl-mononitrate (PE-mono-N) in human plasma. Therefore, in order to determine PETN and its metabolites in plasma sensitive and highly selective GC/MS methods had to be developed and validated. PETN and its metabolite PE-tri-N were validated in the concentration range 50 pg/ml to 10 ng/ml. Isosorbide dinitrate (ISDN) was used as the internal standard and the analytes were extracted with dichloromethane from the plasma. The mass spectrometric tests were carried out using chemical ionization in the negative mode (NlCl) with the application of ammonia as a reagent gas. The nitrate ion m/z 62 was determined in the analytes and internal standard. The accuracy of the mean of the quality control samples during the three days (between days) was between 100 and 110% (PETN), as well as 90 and 106% (PE-tri-N). After an oral application of 100 mg PETN in a pilot study, unchanged PETN and PE-tri-N was measured in plasma. Both metabolites PE-di-N and PE-mono-N were validated at the concentration range of 0.25 ng/ml to 25 ng/ml plasma. After extraction, these analytes were derivatized with BSTFA (N,O-bis[trimethylsilyl]trifluoro-acetamide). The applied internal standard was isosorbide-5-mononitrate (IS-5-MN). The mass spectrometric tests were carried out in the same manner as for PETN and PE-tri-N with chemical ionization in the NlCl mode. The detected masses were m/z 324 for PE-di-N, m/z 351 for PE-mono-N and m/z 217 for IS-5-MN. The accuracy of the mean of the quality control samples during 5 days were between 104 and 107% (PE-di-N) and 102 and 106% (PE-mono-N). The maximum concentration of these analytes in the subject samples were on the average all over 5 ng/ml plasma after the oral administration of 100 mg PETN.
Asunto(s)
Tetranitrato de Pentaeritritol/sangre , Vasodilatadores/sangre , Calibración , Cromatografía de Gases y Espectrometría de Masas , Humanos , Tetranitrato de Pentaeritritol/farmacocinética , Vasodilatadores/farmacocinéticaRESUMEN
Two preparations containing 100 mg pentaerithyrityl tetranitrate (PETN, CAS 78-11-5) each were administered to 24 healthy male volunteers in an open randomised two-way cross-over design. The test preparation was a commercially available 50 mg tablet (Pentalong 50 mg Tabletten, 2 tablets per dose), the reference preparation was an aqueous suspension prepared immediately before application from the same 25% PETN/lactose trituration as was used for manufacturing the tablets. Blood samples were withdrawn pre-dose and at 14 time points within 24 h after dosing. The resulting plasma was analysed by a GC/MS method developed on purpose. Since in a pilot study not a single one of 120 plasma samples contained concentrations of unchanged PETN or of its metabolite pentaerithrityl trinitrate (PE-tri-N, CAS 1607-17-6) above the quantification limit of 50 pg/ml, the samples of this study were assayed for the metabolites pentaerithrityl dinitrate (PE-di-N, CAS 1607-01-8) and pentaerithrityl mononitrate (PE-mono-N, CAS 1607-00-7) only. -Mean peak levels of 17 ng/ml and 7.5 ng/ml PE-di-N were reached ca. 3 h after application of tablets or trituration. The plasma elimination half-life was 4-5 h. Average maximum PE-mono-N levels of 79 ng/ml (tablets) and 35 ng/ml (trituration) were observed at 7 h p. appl. They declined with a half-life of 10-11 h. The relative bioavailability of the tablets as determined by means of the AUC of PE-di-N is 280-290%. This high value is explained by the specific properties of drug liberation and dissolution from the preparations used.