WHAT IS ALREADY KNOWN ABOUT THIS SUBJECT• Cranberry juice has a significant inhibitory effect on CYP2C9 activity in vitro, whereas it shows a minimal effect on the pharmacokinetics and pharmacodynamics of warfarin, a CYP2C9 substrate in vivo.• Information regarding the interaction between cranberry juice and other medications metabolized by CYP2C9 is limited. WHAT THIS STUDY ADDS• Cranberry juice suppressed the metabolism of diclofenac, another CYP2C9 substrate, by human liver microsomes.• Pharmacokinetic parameters of diclofenac were not altered by cranberry juice consumption in human subjects. AIMTo investigate a potential interaction between cranberry juice and diclofenac, a substrate of CYP2C9. METHODSThe inhibitory effect of cranberry juice on diclofenac metabolism was determined using human liver microsome assay. Subsequently, we performed a clinical trial in healthy human subjects to determine whether the repeated consumption of cranberry juice changed the diclofenac pharmacokinetics. RESULTSCranberry juice significantly suppressed diclofenac metabolism by human liver microsomes. On the other hand, repeated consumption of cranberry juice did not influence the diclofenac pharmacokinetics in human subjects. CONCLUSIONSCranberry juice inhibited diclofenac metabolism by human liver microsomes, but not in human subjects. Based on the present and previous findings, we think that although cranberry juice inhibits CYP2C9 activity in vitro, it does not change the pharmacokinetics of medications metabolized by CYP2C9 in clinical situations.

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1. The aims were to attest whether HepG2-GS-3A4, a cell line into which the human CYP3A4 gene was introduced, can be used for a screening of chemicals that will inhibit CYP3A4 activity. 2. The capacity of the cells for metabolizing CYP3A4 substrates in vitro was evaluated. Also determined was the effect of CYP3A4 inhibitors and non-inhibitors on nifedipine hydroxylation. Western blot, immunohistochemostry and determination of beta-nicotinamide adenine dinucleotide phosphate (NADPH)-reductase activity were performed. 3. HepG2-GS-3A4 selectively metabolized substrates of CYP3A4 (diazepam, nordiazepam, lidocaine, atorvastatin, and nifedipine) to a greater degree than control. The metabolites were easily detected in the culture medium. Values of V(max) of HepG2-GS-3A4 were about 30- to 100-fold higher than those of the control, while values of K(m) were comparable. Pre-incubation of cimetidine and ketoconazole significantly inhibited nifedipine hydroxylation, while addition of inhibitors specific to other isoforms of CYPs had no substantial effect. The HepG2-GS-3A4 expressed a higher amount of CYP3A4 protein and mRNA than control. Most NADPH reductase activity was detected in microsomal fractions. 4 In conclusion, HepG2-GS-3A4 sufficiently and selectively metabolize substrates of CYP3A4, and inhibitors of CYP3A4 reduced the metabolism. Because the metabolites were easily detected in the culture medium, this cell might be useful for the new and easy screening of new drugs for the evaluation of CYP3A4-inhibiting activity in vitro.

The chronopharmacological effect of raloxifene, a selective estrogen-receptor modulator, was evaluated by repeated dosing of ovariectomized rats. Bilateral ovariectomy or sham operation was performed at age 12 wks, and animals were kept in rooms with a 12 h light-12 h dark cycle. Raloxifene (3 mg/kg, once daily for 10 wks) or vehicle was given repeatedly at either 2 h after lights-on (2 HALO) or 14 h after lights-on (14 HALO). Plasma fibrinogen concentration at the end of the study was reduced by the drug, and the reduction was significantly prominent in rats in whom the drug was dosed at 2 HALO rather than 14 HALO. Femur bone density decreased, and urinary excretion of deoxypyridinoline, an index of bone resorption capacity of osteoclasts, increased in ovariectomized animals at the end of the study. Treatment with raloxifene ameliorated these changes in a dosing time-independent manner. Serum calcium, ALT, and total protein concentrations at the end of the study also did not differ according to treatment regime, which indicates that protein synthesis and liver function may not contribute to the effects. This is the first study to determine dosing time-dependent changes in the efficacy of raloxifene in an animal model of osteoporosis. Because fibrinogen concentration is reported to be a marker of cardiovascular events, consideration of dosing time of raloxifene may be important to obtain a better cardioprotective effect of this medication when it is prescribed to postmenopausal women with osteoporosis.

We concluded that inhibition of CYP3A4 activity by DHB includes the inhibition of POR activity. HepG2-GS-3A4 might be a good tool to evaluate the mechanisms.