Effect of Cyclosporine and Tacrolimus on Cytochrome P450 Activities in Human Liver Microsomes

Abstract

The eŠects of cyclosporine and tacrolimus on cytochrome P450 (CYP) 1A2-mediated 7-ethoxyresoruˆn O-deethylation, CYP2C9-mediated tolbutamide hydroxylation, CYP2C19-mediated S-mephenytoin 4′ -hydroxylation, CYP2D6-mediated debrisoquine 4-hydroxylation, CYP2E1-mediated chlorzoxazone 6-hydroxylation, CYP3A4-mediated nifedipine oxidation, and CYP3A4-mediated testosterone 6b-hydroxylation activities in human liver microsomes were compared. Cyclosporine and tacrolimus, at concentrations of 0.2 or 2 mM, neither inhibited nor stimulated any of the metabolic activities except for those of CYP3A4. On the other hand, cyclosporine and tacrolimus competitively inhibited CYP3A4-mediated nifedipine oxidation activity, with inhibition constants (K i ) of 1.42 and 0.36 mM, respectively. In addition, 20 mM cyclosporine inhibited CYP2C19 and CYP2D6 activities by 29％ and 30％, respectively. These results suggest that tacrolimus would not cause clinically signiˆcant interactions with other drugs, which are metabolized by CYPs, via the inhibition of hepatic metabolism and that the reason why cyclosporine, but not tacrolimus, has a pharmacokinetic inhibitory eŠect might be that the dosage and/or the unbound concentrations around its metabolic enzymes are higher than those of tacrolimus, rather than the diŠerences in the inhibition potential. Obvious substrate-dependent eŠects on CYP3A4-inhibition potential were not observed.

Effect of penicillin-based antibiotics, amoxicillin, ampicillin, and piperacillin, on drug-metabolizing activities of human hepatic cytochromes P450

“…The metabolic activities of recombinant P450s in the absence of penicillin-based antibiotics were similar to those reported previously (Niwa et al, 1999(Niwa et al, , 2005(Niwa et al, and 2007. CYP2C9-mediated tolbutamide methylhydroxylation, CYP2D6-mediated dopamine formation, and CYP3A4 and CYP3A5-mediated testosterone 6β-hydroxylation in the presence of the penicillin-based antibiotics at a concentrations of 0.1-1 mM were 87%-111% of control, indicating that these penicillin-based antibiotics had neither inhibitory nor stimulatory effects against these P450s.…”

“…Incubation times were 5 (for aminopyrine N-demethylation and testosterone 6β-hydroxylation), 10 (for dopamine formation), or 60 min (for tolbutamide methylhydroxylation). Concentrations of aminopyrine, tolbutamide, p-tyramine, and testosterone were 5,000, 400, 60, and 60 μM, respectively; which are around the expected K m (Niwa et al, 1999(Niwa et al, , 2005(Niwa et al, and 2007. All data were analyzed using the average of triplicate determinations.…”

“…Aminopyrine N-demethylation (CYP2C8), tolbutamide methylhydroxylation (CYP2C9), dopamine formation (CYP2D6), and testosterone 6β-hydroxylation (CYP3A4 and CYP3A5) were determined in the presence or absence of amoxicillin, ampicillin, and piperacillin, as described previously (Niwa et al, 1999(Niwa et al, , 2005(Niwa et al, and 2007. The incubation mixture consisted of human P450, 1 mM NADPH, and 100 mM potassium phosphate buffer (pH 7.4) in a final volume of 0.5 mL.…”

Cyclosporine A, but Not Tacrolimus, Shows Relevant Inhibition of Organic Anion-Transporting Protein 1B1-Mediated Transport of Atorvastatin

“…Inhibition of CYP3A4 or inhibition of P-gp or a combination of CYP3A4 and P-gp inhibition has also been suggested to play a role in this interaction. However, inhibition of CYP3A4 by CsA is probably of limited relevance considering the relatively high K i values reported (Wandel et al, 1999;Niwa et al, 2007) and the phenotypic findings by Lemahieu et al (2005) showing no reduction in CYP3A4 activity after CsA treatment. P-gp activity seems to be roughly halved by concomitant CsA treatment (Lemahieu et al, 2005), suggesting that OATP1B1 may be the most important factor in the interaction between atorvastatin and CsA.…”

“…By using the total concentration of CsA in the estimations, inhibition of OATP1B1-mediated uptake of atorvastatin ranged from 94 to 99% with preincubation and from 42 to 82% with coincubation in the dose interval. The maximal inhibition of OATP1B1-mediated uptake by Tac was estimated to be 0.77% when we considered the maximum total concentration at the inlet to the liver, estimated on the basis of a C max value of 0.097 M (78 ng/ml) (Niwa et al, 2007).…”