Warfarin is an anticoagulant drug, one of the most used for the prevention of thromboembolic events. This thesis work aims to evaluate the possible drug-drug interactions involving warfarin and some antibacterial therapies. The data collected at the Culzoni Pharmacy in Settimo Milanese evaluated 10 patients in TAO with warfarin with a significant fluctuation of the INR. Warfarin is administered as an equimolar racemate of R- and S-warfarin. About 20% of the administered dose is reduced to alcohol derivatives, with the formation of a second chiral center in position 11. The metabolization of the remaining 80% is carried out by the hepatic P-450: S-warfarin is mainly transformed into S-7 - and S-6-hydroxywarfarin from CYP2C9 in a 3: 1 ratio. CYP2C19, CYP1A1 and CYP1A2 also show activity against this substrate. R-warfarin, on the other hand, is mainly metabolised by CYP3A4, and its major metabolite 10-hydroxywarfarin is the second most present metabolite in human plasma. Another criticality is the inhibition of the hydroxylase activity of CYP2C9 by R-warfarin and the hydroxylated metabolites: the results indicate that 10-hydroxywarfarin is the major inhibitor, with Ki approximately 2.5 times lower than the Km of S-warfarin , while R-warfarin shows a Ki of about 2.5 times higher than the Km of the substrate. It was also observed that R-warfarin and 10-hydroxywarfarin can increase the expression of CYP3A4 and CYP2C9 in the liver through interaction with PXR. The clearance of monohydroxylated metabolites could therefore play a critical role in determining the therapeutic outcome, which is why the analysis of phase II metabolic pathways has been more in-depth in recent decades; the data show that R-, S- and rac-warfarin are not substrates for human UGT. In increasing order 4'- 6-, 7- and 8-hydroxywarfarin are the monohydroxylated metabolites preferred by UGT 1A1, 1A9 and 1A6. The analysis of the metabolism of warfarin is of vital importance to evaluate the possible interactions reported (amoxicillin, ciprofloxacin, clarithromycin and levofloxacin) and has shown that the clearance of warfarin is dominated by a complex metabolic pathway. Case reports describing these hypoprothrombinemic events during concomitant intake of warfarin and the antibacterials mentioned are available in the literature, but in general, prospective clinical studies have had little ability to notice statistically significant coagulation changes. Ciprofloxacin was shown on day 12 of therapy to significantly reduce clotting factor II and clotting factor VII concentrations and to increase R-warfarin concentration. An increase in mean PT of 3% was also noted, but none of the patients experienced any bleeding events. Clarithromycin has been shown to decrease intestinal CYP3A activity by 64% after the first dose administered and to decrease hepatic CYP3A activity by approximately 50% during therapy. For levofloxacin, a supratherapeutic INR was found in 7 (32%) of the treated patients and in 3 (14%) of the control patients, while the patients with an increase greater than 1.0 were 18% and 5% respectively. Three patients in the levofloxacin group and none in the control group achieved INR greater than 4.0. The case reports are therefore in disagreement with clinical studies and this can derive from different causes: unrecognized confounding factors, studies with too few patient groups, alteration of the intestinal bacterial flora, pharmacokinetic interactions and inhibition of hepatic CYPs during states of inflammation or infection. Although significant evidence of these possible interactions does not exist, healthcare professionals need to monitor for possible signs of over-anticoagulation during and after antibacterial therapy.
Il warfarin è un farmaco anticoagulante, uno dei più utilizzati per la prevenzione di eventi tromboembolici. L'elaborato di tesi si pone l’obbiettivo di valutare le possibili interazioni che coinvolgono il warfarin ed alcune terapie antibatteriche. I dati raccolti presso la Farmacia Culzoni di Settimo Milanese hanno valutato 10 pazienti in TAO con warfarin con una fluttuazione importante dell’INR. Warfarin è somministrato come racemato di R- ed S-warfarin. Circa il 20% della dose somministrata viene ridotta in alcol derivati, con la formazione di un secondo centro chirale in posizione 11. La metabolizzazione del restante 80% è a carico dei P-450 epatici: S-warfarin è trasformato principalmente in S-7- e S-6-idrossiwarfarin da CYP2C9 in rapporto 3:1. Anche CYP2C19, CYP1A1 e CYP1A2 mostrano attività verso questo substrato. R-warfarin invece è metabolizzato principalmente da CYP3A4, ed il suo metabolita principale 10-idrossiwarfarin è il secondo metabolita maggiormente presente nel plasma umano. Altra criticità è l’inibizione dell’attività idrossilasica di CYP2C9 da parte di R-warfarin e dei metaboliti idrossilati: i risultati indicano come 10-idrossiwarfarin sia il maggior inibitore, con Ki di circa 2,5 volte inferiore alla Km di S-warfarin, mentre R-warfarin dimostra una Ki di circa 2,5 volte superiore alla Km del substrato. È stato inoltre osservato come R-warfarin e 10-idrossiwarfarin possano aumentare l’espressione di CYP3A4 e CYP2C9 a livello epatico tramite l’interazione con PXR. La clearance dei metaboliti monoidrossilati potrebbe quindi svolgere un ruolo critico nel determinare l’esito terapeutico, per questo negli ultimi decenni l’analisi delle vie di metabolizzazione di fase II è stata maggiormente approfondita; i dati mostrano come R-, S- e rac-warfarin non siano substrati per le UGT umane. In ordine crescente 4’- 6-, 7- ed 8-idrossiwarfarin sono i metaboliti monoidrossilati preferiti dalle UGT 1A1, 1A9 e 1A6. L’analisi del metabolismo di warfarin è di vitale importanza per valutare le possibili interazioni riportate (amoxicillina, ciprofloxacina, claritromicina e levofloxacina) ed ha dimostrato come la clearance di warfarin sia dominata da una complessa via metabolica. In letteratura sono disponibili case reports che descrivono questi eventi ipoprotrombinemici durante la concomitante assunzione di warfarin e gli antibatterici citati, ma in generale gli studi clinici prospettici hanno avuto scarsa capacità di notare variazioni coagulative statisticamente significative. Ciprofloxacina ha sì dimostrato al giorno 12 di terapia di ridurre in modo significativo le concentrazioni del fattore di coagulazione II e del fattore di coagulazione VII e di aumentare la concentrazione di R-warfarin. È stato anche notato un aumento del PT medio del 3%, ma nessuno dei pazienti ha riscontrato eventi di sanguinamento. Claritromicina ha dimostrato di diminuire l’attività di CYP3A intestinale del 64% dopo la prima dose somministrata e di diminuire di circa il 50% l’attività di CYP3A epatico durante la terapia. Per levofloxacina un INR sovraterapeutico è stato riscontrato in 7 (32%) dei pazienti trattati ed in 3 (14%) dei pazienti controllo, mentre i pazienti con aumento maggiore di 1,0 erano il 18% ed il 5% rispettivamente. Tre pazienti del gruppo levofloxacina e nessuno del gruppo di controllo hanno ottenuto INR superiore a 4,0. I case reports sono quindi in disaccordo con gli studi clinici e questo può derivare da differenti cause: fattori confondenti non riconosciuti, studi con gruppi di pazienti troppo poco numerosi, alterazione della flora batterica intestinale, interazioni farmacocinetiche ed inibizione dei CYP epatici durante stati di infiammazione o di infezione. Sebbene una significativa dimostrazione di queste possibili interazioni non esista, è necessario che gli operatori sanitari monitorino durante e dopo la terapia antibatterica possibili segnali di over-anticoagulazione.
Warfarin ed antibatterici: meccanismi di interazione ed analisi di INR over-terapeutici individuati grazie alla farmacia dei servizi
BONAZZOLI, DAVIDE
2019/2020
Abstract
Warfarin is an anticoagulant drug, one of the most used for the prevention of thromboembolic events. This thesis work aims to evaluate the possible drug-drug interactions involving warfarin and some antibacterial therapies. The data collected at the Culzoni Pharmacy in Settimo Milanese evaluated 10 patients in TAO with warfarin with a significant fluctuation of the INR. Warfarin is administered as an equimolar racemate of R- and S-warfarin. About 20% of the administered dose is reduced to alcohol derivatives, with the formation of a second chiral center in position 11. The metabolization of the remaining 80% is carried out by the hepatic P-450: S-warfarin is mainly transformed into S-7 - and S-6-hydroxywarfarin from CYP2C9 in a 3: 1 ratio. CYP2C19, CYP1A1 and CYP1A2 also show activity against this substrate. R-warfarin, on the other hand, is mainly metabolised by CYP3A4, and its major metabolite 10-hydroxywarfarin is the second most present metabolite in human plasma. Another criticality is the inhibition of the hydroxylase activity of CYP2C9 by R-warfarin and the hydroxylated metabolites: the results indicate that 10-hydroxywarfarin is the major inhibitor, with Ki approximately 2.5 times lower than the Km of S-warfarin , while R-warfarin shows a Ki of about 2.5 times higher than the Km of the substrate. It was also observed that R-warfarin and 10-hydroxywarfarin can increase the expression of CYP3A4 and CYP2C9 in the liver through interaction with PXR. The clearance of monohydroxylated metabolites could therefore play a critical role in determining the therapeutic outcome, which is why the analysis of phase II metabolic pathways has been more in-depth in recent decades; the data show that R-, S- and rac-warfarin are not substrates for human UGT. In increasing order 4'- 6-, 7- and 8-hydroxywarfarin are the monohydroxylated metabolites preferred by UGT 1A1, 1A9 and 1A6. The analysis of the metabolism of warfarin is of vital importance to evaluate the possible interactions reported (amoxicillin, ciprofloxacin, clarithromycin and levofloxacin) and has shown that the clearance of warfarin is dominated by a complex metabolic pathway. Case reports describing these hypoprothrombinemic events during concomitant intake of warfarin and the antibacterials mentioned are available in the literature, but in general, prospective clinical studies have had little ability to notice statistically significant coagulation changes. Ciprofloxacin was shown on day 12 of therapy to significantly reduce clotting factor II and clotting factor VII concentrations and to increase R-warfarin concentration. An increase in mean PT of 3% was also noted, but none of the patients experienced any bleeding events. Clarithromycin has been shown to decrease intestinal CYP3A activity by 64% after the first dose administered and to decrease hepatic CYP3A activity by approximately 50% during therapy. For levofloxacin, a supratherapeutic INR was found in 7 (32%) of the treated patients and in 3 (14%) of the control patients, while the patients with an increase greater than 1.0 were 18% and 5% respectively. Three patients in the levofloxacin group and none in the control group achieved INR greater than 4.0. The case reports are therefore in disagreement with clinical studies and this can derive from different causes: unrecognized confounding factors, studies with too few patient groups, alteration of the intestinal bacterial flora, pharmacokinetic interactions and inhibition of hepatic CYPs during states of inflammation or infection. Although significant evidence of these possible interactions does not exist, healthcare professionals need to monitor for possible signs of over-anticoagulation during and after antibacterial therapy.È consentito all'utente scaricare e condividere i documenti disponibili a testo pieno in UNITESI UNIPV nel rispetto della licenza Creative Commons del tipo CC BY NC ND.
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https://hdl.handle.net/20.500.14239/13229