Influence of verapamil on the pharmacokinetics of rotundic acid in rats and its potential mechanism

ContextRotundic acid (RA), a plant-derived pentacyclic triterpene acid, has been reported to possess extensive pharmacological activities. The poor bioavailability limits its further development and potential clinic application.ObjectiveTo clarify the potential mechanism for poor oral bioavailability.Materials and methodsThe single-dose pharmacokinetics of orally administered RA (10 mg/kg) in Sprague–Dawley rats without or with verapamil (25 or 50 mg/kg) were investigated. Additionally, MDCKII-MDR1 and Caco-2 cell monolayers, five recombinant human cytochrome P450 (rhCYP) enzymes (1A2, 2C8, 2C9, 2D6 and 3A4), and rat liver microsomes were also conducted to investigate its potential mechanism.ResultsVerapamil could significantly affect the plasma concentration of RA. Co-administered verapamil at 25 and 50 mg/kg, the AUC_0–∞ increased from 432 ± 64.2 to 539 ± 53.6 and 836 ± 116 ng × h/mL, respectively, and the oral clearance decreased from 23.6 ± 3.50 to 18.7 ± 1.85 and 12.2 ± 1.85 L/h/kg, respectively. The MDCKII-MDR1 cell assay showed that RA might be a P-gp substrate. The rhCYPs experiments indicated that RA was mainly metabolized by CYP3A4. Additionally, verapamil could increase the absorption of RA by inhibiting the activity of P-gp, and slow down the intrinsic clearance of RA from 48.5 ± 3.18 to 12.0 ± 1.06 µL/min/mg protein.Discussion and conclusionsThese findings indicated that verapamil could significantly affect the pharmacokinetic profiles of RA in rats. It was demonstrated that P-gp and CYP3A were involved in the transport and metabolism of RA, which might contribute to the low oral bioavailability of RA.     

Pioglitazone, an in vitro inhibitor of CYP2C8 and CYP3A4, does not increase the plasma concentrations of the CYP2C8 and CYP3A4 substrate repaglinide

Objective Pioglitazone, a thiazolidinedione antidiabetic, inhibits cytochrome P450 (CYP) 2C8 and CYP3A4 enzymes in vitro. Repaglinide, a meglitinide analogue antidiabetic, is metabolised by CYP2C8 and CYP3A4. In patients with type 2 diabetes, the pioglitazone-repaglinide combination has acted synergistically on glycaemic parameters. Our aim was to determine whether pioglitazone increases the plasma concentrations of repaglinide. Methods In a randomized, 2-phase cross-over study, 12 healthy volunteers received 30 mg pioglitazone or placebo once daily for 5 days. On day 5, they ingested a single 0.25 mg dose of repaglinide 1 h after the last pretreatment dose. Plasma repaglinide and pioglitazone, and blood glucose concentrations were measured for 12 h. Results During the pioglitazone phase, the mean peak plasma repaglinide concentration (C_max) and the total area under the concentration-time curve [AUC(0-∞)] of repaglinide were 100% (range 53–157%, P=0.99) and 90% (range 63–120%, P=0.22), respectively, of those during the placebo phase. Also the half-life of repaglinide was unaffected, but the median peak time of repaglinide was shortened from 40 min to 20 min by pioglitazone (P=0.014). The short-term pioglitazone administration did not modify the blood glucose-lowering effect of a single dose of repaglinide. Conclusions Pioglitazone does not increase the plasma concentrations of repaglinide, indicating that the inhibitory effect of pioglitazone on CYP2C8 and CYP3A4 is very weak in vivo, probably due to its extensive plasma protein binding. The synergistic effect of repaglinide and pioglitazone on the glycaemic parameters, seen in patients with type 2 diabetes during their long-term use, is unlikely to be caused by inhibition of repaglinide metabolism by pioglitazone.     

服用卡马西平癫痫患者CYP3A4基因多态性的研究

目的:研究服用卡马西平癫痫患者细胞色素P4503A4(CYP3A4)的基因多态性,为临床制定卡马西平个体化给药方案提供依据。方法:收集临床服用卡马西平癫痫患者的血标本,用聚合酶链反应-限制性片段长度多态性(PCR-RFLP)法检测CYP3A4的突变。结果:141例患者中存在CYP3A4*4、CYP3A4*6的突变,个体突变率均为0.71%;未见CYP3A4*5的突变。结论:2例突变型标本与其他标本的血药浓度与临床疗效比较无显著性差异,不能说明CYP3A4*4、CYP3A4*6的突变对其表达的药物代谢酶的活性有影响。     

卡马西平健康人体药物动力学特性

目的:建立测定卡马西平(CBZ)的高效液相色谱法。分析CBZ在健康受试者体内药动学特性,探讨临床应用个体差异的原因。方法:12名健康受试者单剂量(200 mg)口服CBZ片,HPLC法测定血浆样品药物浓度。结果:CBZ的线性范围为(0.05～10)μg·ml~(-1),最低检测浓度为0.05μg·ml~(-1),方法平均回收率为94.4%。单剂量口服CBZ后血浆浓度符合一级吸收一房室模型,其主要药动学参数为:C_(max)为(4.71±0.99)μg·ml~(-1),t_(max)为(16±12)h,AUC为(361.62±49.43)μg·h·ml~(-1),t_(1/2)= (38.39±6.37)h。结论:该法测定血浆中CBZ浓度高效、灵敏、准确,CBZ体内药动学特性存在明显个体差异。     

Methadone—metabolism, pharmacokinetics and interactions

The pharmacokinetics of methadone varies greatly from person to person; so, after the administration of the same dose, considerably different concentrations are obtained in different subjects, and the pharmacological effect may be too small in some patients, too strong and prolonged in others. Methadone is mostly metabolised in the liver; the main step consists in the N-demethylation by CYP3A4 to EDDP (2-ethylidene-1,5-dimethyl-3,3-diphenylpyrrolidine), an inactive metabolite. The activity of CYP3A4 varies considerably among individuals, and such variability is the responsible for the large differences in methadone bioavailability. CYP2D6 and probably CYP1A2 are also involved in methadone metabolism. During maintenance treatment with methadone, treatment with other drugs may be necessary due to the frequent comorbidity of drug addicts: psychotropic drugs, antibiotics, anticonvulsants and antiretroviral drugs, which can cause pharmacokinetic interactions. In particular, antiretrovirals, which are CYP3A4 inducers, can decrease the levels of methadone, so causing withdrawal symptoms. Buprenorphine, too, is metabolised by CYP3A4, and may undergo the same interactions as methadone. Since it is impossible to foresee the time-lapse from the administration of another drug to the appearing of withdrawal symptoms, nor how much the daily dose of methadone should be increased in order to prevent them, patients taking combined drug treatments must be carefully monitored. The so far known pharmacokinetic drug-drug interactions of methadone do not have life-threatening consequences for the patients, but they usually cause a decrease of the concentrations and of the effects of the drug, which in turn can cause symptoms of withdrawal and increase the risk of relapse into heroin abuse.     

The pharmacokinetic study on the interaction between nobiletin and anemarsaponin BII in vivo and in vitro

ContextThe interaction between nobiletin and anemarsaponin BII could affect the pharmacological activity of these two drugs during their combination.ObjectiveThe co-administration of nobiletin and anemarsaponin BII was investigated to explore the interaction and the potential mechanism.Materials and methodsMale Sprague-Dawley rats were only orally administrated with 50 mg/kg nobiletin as the control and another six rats were pre-treated with 100 mg/kg anemarsaponin BII for 7 d followed by the administration of nobiletin. The transport and metabolic stability of nobiletin were evaluated in vitro, and the effect of anemarsaponin BII on the activity of CYP3A4 was also assessed to explore the potential mechanism underlying the interaction.ResultsThe increasing C_max (2309.67 ± 68.06 μg/L vs. 1767.67 ± 68.86 μg/L), AUC (28.84 ± 1.34 mg/L × h vs. 19.57 ± 2.76 mg/L × h), prolonged t_1/2 (9.80 ± 2.33 h vs. 6.24 ± 1.53 h), and decreased clearance rate (1.46 ± 0.26 vs. 2.42 ± 0.40) of nobilein was observed in rats. Anemarsaponin BII significantly enhanced the metabolic stability of nobiletin in rat liver microsomes (half-life increased from 31.56 min to 39.44 min) and suppressed the transport of nobiletin in Caco-2 cells (efflux rate decreased from 1.57 ± 0.04 to 1.30 ± 0.03). The inhibitory effect of anemarsaponin BII on CYP3A4 was also found with an IC₅₀ value of 10.23 μM.Discussion and conclusionsThe interaction between anemarsaponin BII and nobiletin was induced by the inhibition of CYP3A4, which should draw special attention in their clinical co-administration.     

Effects of oral clotrimazole troches on the pharmacokinetics of oral and intravenous midazolam

AIMS

The aim of the study was to determine the effects of oral clotrimazole troches on the pharmacokinetics of oral and intravenous midazolam in the plasma.

METHODS

We conducted a randomized, open-label, four-way crossover study in 10 healthy volunteers. Each volunteer received oral midazolam 2 mg or intravenous midazolam 0.025 mg kg⁻¹ with and without oral clotrimazole troches 10 mg taken three times daily for 5 days. Each study period was separated by 14 days. Serial blood samples were collected up to 24 h after oral midazolam and 6 h after intravenous midazolam. Plasma concentrations for midazolam and its metabolite 1-hydroxymidazolam were measured and fitted to a noncompartmental model to estimate the pharmacokinetic parameters.

RESULTS

Ten healthy volunteers aged 21–26 years provided written informed consent and were enrolled into the study. Clotrimazole decreased the apparent oral clearance of midazolam from 57 ± 13 l h⁻¹[95% confidence interval 48, 66] to 36 ± 9.8 l h⁻¹ (95% confidence interval 29, 43) (P= 0.003). These changes were accompanied by a decrease in the area under the concentration–time curve (mean difference 22 µg h⁻¹ l⁻¹, P= 0.001) and bioavailability (mean difference 0.21, P= NS). There were no significant differences in the systemic clearance of midazolam with or without clotrimazole troches.

CONCLUSIONS

Oral clotrimazole troches decreased the apparent oral clearance of midazolam; no significant differences in the systemic clearance of midazolam were found.     

Effect of ketoconazole and diltiazem on the pharmacokinetics of apixaban,an oral direct factor Xa inhibitor

Aim

Apixaban is an orally active inhibitor of coagulation factor Xa and is eliminated by multiple pathways, including renal and non-renal elimination. Non-renal elimination pathways consist of metabolism by cytochrome P450 (CYP) enzymes, primarily CYP3A4, as well as direct intestinal excretion. Two single sequence studies evaluated the effect of ketoconazole (a strong dual inhibitor of CYP3A4 and P-glycoprotein [P-gp]) and diltiazem (a moderate CYP3A4 inhibitor and a P-gp inhibitor) on apixaban pharmacokinetics in healthy subjects.

Method

In the ketoconazole study, 18 subjects received apixaban 10 mg on days 1 and 7, and ketoconazole 400 mg once daily on days 4–9. In the diltiazem study, 18 subjects received apixaban 10 mg on days 1 and 11 and diltiazem 360 mg once daily on days 4–13.

Results

Apixaban maximum plasma concentration and area under the plasma concentration–time curve extrapolated to infinity increased by 62% (90% confidence interval [CI], 47, 78%) and 99% (90% CI, 81, 118%), respectively, with co-administration of ketoconazole, and by 31% (90% CI, 16, 49%) and 40% (90% CI, 23, 59%), respectively, with diltiazem.

Conclusion

A 2-fold and 1.4-fold increase in apixaban exposure was observed with co-administration of ketoconazole and diltiazem, respectively.     

Pharmacokinetics of eribulin mesylate in patients with solid tumours receiving repeated oral rifampicin

Aim

Eribulin mesylate is a non-taxane microtubule dynamics inhibitor that was recently approved for treatment of metastatic breast cancer. The aim of this study was to determine the effect of rifampicin, a CYP3A4 inducer, on the plasma pharmacokinetics of eribulin in patients with solid tumours.

Methods

An open-label, non-randomized phase I study was carried out. Patients received intravenous 1.4 mg m⁻² eribulin mesylate on days 1 and 15 and oral rifampicin 600 mg on days 9 to 20 of a 28 day cycle. Pharmacokinetic sampling for determination of eribulin plasma concentrations was performed up to 144 h following administration. AUC(0,∞) and C_max for eribulin exposure without or with co-administration of rifampicin were subjected to an analysis of variance (anova) and corresponding 90% confidence intervals (CI) were calculated. Subsequently, patients were allowed to continue eribulin mesylate treatment with 1.4 mg m⁻² eribulin mesylate on days 1 and 8 of a 21 day cycle. Also the adverse event profile and anti-tumour activity were assessed.

Results

Fourteen patients were included and 11 patients were evaluable for pharmacokinetic analysis. Co-administration of rifampicin had no effect on single dose exposure to eribulin (geometric least square means ratio: AUC(0,∞) = 1.10, 90% CI 0.91, 1.34 and C_max = 0.97, 90% 0.81, 1.17). The most common treatment-related grade ≥3 adverse events were grade 3 neutropenia (4/14, 29%), leucopenia and fatigue (both 3/14, 21%).

Conclusions

These results indicate that eribulin mesylate may be safely co-administered with compounds that are CYP3A4 inducers.     

Effect of pioglitazone on the pharmacokinetics of verapamil and its major metabolite,norverapamil, in rats

Pioglitazone, a thiazolidinedione antidiabetic drug, inhibits cytochrome P450 (CYP) 2C8 and CYP3A4 enzymes in vitro. This study investigated the effect of pioglitazone on the pharmacokinetics of verapamil and its major metabolite, norverapamil, in rats, after oral administration of verapamil (9 mg/kg) in the presence or absence of pioglitazone (0.3 or 1.0 mg/kg). Pioglitazone altered verapamil pharmacokinetics compared with verapamil alone. The presence of 1.0 mg/kg of pioglitazone significantly (p < 0.05) increased the area under the plasma concentration-time curve (AUC) and the peak concentration (C(max)) of verapamil by 49.0% and 46.8%, respectively, and significantly (p < 0.05) decreased the total plasma clearance (CL/F) of verapamil by 32.8%. The metabolite-parent AUC ratio in the presence of pioglitazone (1.0 mg/kg) significantly (p < 0.05) decreased by 21.9% compared to the control group. Thus, coadministration of pioglitazone inhibited the CYP3A4-mediated metabolism of verapamil.     

辛伐他汀和阿托伐他汀与CYP3A4酶抑制剂/诱导剂在心内科患者中联用情况调查

目的:调查临床治疗中辛伐他汀和阿托伐他汀与CYP3A4酶抑制剂/诱导剂联合使用的情况。方法:随机抽取某三甲医院2012年度心内科应用辛伐他汀和阿托伐他汀的病例各50份,应用SPSS18.0统计软件,对患者的一般状况、用药情况及化验指标进行统计分析,计算各项指标的平均值或比例。结果:本调查纳入100名患者,66%的患者在使用辛伐他汀或阿托伐他汀的同时使用CYP3A4酶抑制剂,其中,辛伐他汀占30%,阿托伐他汀占36%,平均联合用药时间为(7.04±0.29)d。联合使用的CYP3A4酶抑制剂药物有氨氯地平片、地尔硫片、雷尼替丁片、胺碘酮、银杏叶片;CYP3A4酶诱导剂药物主要有卡马西平和醋酸泼尼松龙片。辛伐他汀或阿托伐他汀与CYP3A4酶抑制剂联合使用频率远远多于与CYP3A4酶诱导剂联合使用频率。比较合用和无合用CYP3A4酶抑制剂患者的主要生化指标,差异无统计学意义(P>0.05)。结论:辛伐他汀或阿托伐他汀与CYP3A4酶抑制剂联合使用情况在该医院较常见。建议尽量避免联用具有相互作用的药物,如必须使用,应按说明书要求不超剂量用药,并充分关注药物相互作用导致的不良反应,对患者后续情况定期随访。     

Effect of fluvoxamine on plasma risperidone concentrations in patients with schizophrenia

The effect of fluvoxamine on plasma concentrations of risperidone and its active metabolite 9-hydroxyrisperidone (9-OH-risperidone) was investigated in 11 schizophrenic patients with prevailingly negative or depressive symptoms. Additional fluvoxamine, at the dose of 100 mg/day, was administered for 4 weeks to patients stabilized on risperidone (3-6 mg/day). Mean plasma concentrations of risperidone, 9-OH-risperidone and the active moiety (sum of the concentrations of risperidone and 9-OH-risperidone) were not significantly modified following co-administration with fluvoxamine. After 4 weeks, fluvoxamine dosage was increased to 200 mg/day in five patients and then maintained until the end of week 8. At final evaluation, mean plasma levels of risperidone active moiety were not modified in the six patients who were still receiving the initial fluvoxamine dose, while concentrations increased slightly but significantly (by a mean 26% over pretreatment; P < 0.05) in the subgroup of five subjects treated with a final dose of 200 mg/day. Fluvoxamine co-administration with risperidone was well tolerated and no patient developed extrapyramidal side effects. These findings indicate that fluvoxamine at dosages up to 100 mg/day is not associated with clinically significant changes in plasma risperidone concentrations. However, higher doses of fluvoxamine may elevate plasma risperidone levels, presumably as a result of a dose-dependent inhibitory effect of fluvoxamine on CYP2D6-and/or CYP3A4-mediated 9-hydroxylation of risperidone.     

4种二氢吡啶类钙拮抗药对地塞米松诱导雌性大鼠CYP3A4酶活性的影响

目的：研究二氢吡啶类钙离子拮抗药（DHPs）中非洛地平、尼卡地平、乐卡地平、硝苯地平对CYP3A4酶活性抑制作用大小,为临床了解DHPs发生药物相互作用的几率大小提供理论基础。方法：采用探针药物法,将经80 mg·kg^-1·d^-1地塞米松诱导3 d的SD雌性大鼠分为阴性对照组、阳性对照组、4种DHPs实验组,每组6只。氨苯砜为探针底物,HPLC法为检测手段,数据通过Win Non Lin药动学分析软件进行模型拟合处理,并通过配对t检验进行统计学分析。结果：阴性对照组与四种DHPs组、阳性对照组氨苯砜的AUC0-24、CL/F值比较有统计学意义（P〈0.05）。4种DHPs对氨苯砜的代谢抑制作用大小分别为硝苯地平〉尼卡地平〉乐卡地平〉非洛地平,但差异无统计学意义（P〉0.05）。而统计学结果显示阳性对照组、4种DHPs组与阴性对照组的Cmax比较,差异无统计学意义（P〉0.05）。结论：虽然不同DHPs对CYP3A4存在不同的抑制作用,但差异在体内表现并不显著,对于非主要通过CYP3A4代谢的共服药物不会产生影响。     

Effect of probenecid on the pharmacokinetics of carbamazepine in healthy subjects

Objectives Carbamazepine (CBZ) undergoes biotransformation by CYP3A4 and CYP2C8, and glucuronide conjugation. There has been no clear demonstration to reveal the role of glucuronidation in the disposition of CBZ. We evaluated the effect of probenecid, a UDP-glucuronosyltransferase inhibitor, on the pharmacokinetics of CBZ in humans.Methods In a randomized, open-label, two-way crossover study, ten healthy male subjects were treated twice daily for 10 days with 500 mg probenecid or with a matched placebo. On day 6, a single dose of 200 mg CBZ was administered orally. Concentrations of CBZ and CBZ 10,11-epoxide (CBZ-E) in plasma and urine were measured.Results Probenecid decreased the area under the plasma concentration–time curve (AUC) of CBZ from 1253.9 mol h/l to 1020.7 mol h/l (P<0.001) while increasing that of CBZ-E from 137.6 mol h/l to 183.5 mol h/l (P=0.033). The oral clearance of CBZ was increased by probenecid by 26% (90% confidence interval, 17–34%; P<0.001). Probenecid increased the AUC ratio of CBZ-E/CBZ from 0.11 to 0.16 (P<0.001). However, probenecid had minimal effect on the recovery of the conjugated and free forms of CBZ and CBZ-E in urine.Conclusion Although probenecid showed a minimal effect on the glucuronidation of CBZ and CBZ-E, it increased CBZ biotransformation to CBZ-E, most likely reflecting the induction of CYP3A4 and CYP2C8 activities, in humans. These results demonstrate that glucuronide conjugation plays a minor role in the metabolism of CBZ and CBZ-E in humans, and that probenecid has an inducing effect on the disposition of CBZ.     

候选新药对大鼠肝细胞色素P4503A4影响的研究

目的研究候选新药(HSH)对大鼠肝细胞色素P4503A4是否有抑制或诱导作用,以及这种作用是否具有性别差异。方法取大鼠雌雄各半,随机分为4个组:雄性对照组(Ⅰ)、雄性给药组(Ⅱ)、雌性对照组(Ⅲ)、雌性给药组(Ⅳ),均采用钙离子沉淀法制备肝微粒体。在各组肝微粒体中同时给予一定剂量的探针药物及目标药物,进行孵育,于不同时间点取样,测定该探针药物的剩余浓度并计算其体外半衰期。结果HSH对肝细胞色素P4503A4无影响。结论就大鼠而言,药物对肝细胞色素P4503A4无影响,HSH在同各种与CYP3A4代谢有关的药物合用时,相对安全。     

Exposure to oral oxycodone is increased by concomitant inhibition of CYP2D6 and 3A4 pathways, but not by inhibition of CYP2D6 alone

AIM

The aim of this study was to find out whether the inhibition of cytochrome P450 2D6 (CYP2D6) with paroxetine or concomitant inhibition of CYP2D6 and CYP3A4 with paroxetine and itraconazole, altered the pharmacokinetics and pharmacological response of orally administered oxycodone.

METHODS

A randomized placebo-controlled cross-over study design with three phases was used. Eleven healthy subjects ingested 10 mg of oral immediate release oxycodone on the fourth day of pre-treatment with either placebo, paroxetine (20 mg once daily) or paroxetine (20 mg once daily) and itraconazole (200 mg once daily) for 5 days. The plasma concentrations of oxycodone and its oxidative metabolites were measured for 48 h, and pharmacological (analgesic and behavioural) effects were evaluated.

RESULTS

Paroxetine alone reduced the area under concentration–time curve (AUC(0,0–48 h)) of the CYP2D6 dependent metabolite oxymorphone by 44% (P < 0.05), but had no significant effects on the plasma concentrations of oxycodone or its pharmacological effects when compared with the placebo phase. When both oxidative pathways of the metabolism of oxycodone were inhibited with paroxetine and itraconazole, the mean AUC(0,∞) of oxycodone increased by 2.9-fold (P < 0.001), and its C_max by 1.8-fold (P < 0.001). Visual analogue scores for subjective drug effects, drowsiness and deterioration of performance were slightly increased (P < 0.05) after paroxetine + itraconazole pre-treatment when compared with placebo.

CONCLUSIONS

Drug interactions arising from CYP2D6 inhibition most likely have minor clinical importance for oral oxycodone if the function of the CYP3A4 pathway is normal. When both CYP2D6 and CYP3A4 pathways are inhibited, the exposure to oral oxycodone is increased substantially.     

伊曲康唑对健康志愿者体内维胺酯药代动力学影响

目的研究伊曲康唑对维胺酯的药代动力学影响,了解维胺酯在人体内的代谢途径和探索其合理联合用药。方法设计两阶段随机双盲交叉试验,8名健康男性受试者首先口服伊曲康唑200 mg或安慰剂,每天1次,连续服用5 d,在d 4,空腹口服维胺酯100 mg,利用液相色谱质谱联用法(LC-MS)测量血浆中维胺酯浓度。结果合用伊曲康唑后维胺酯平均峰浓度增加[(21.21±11.65)μg.L-1vs(27.12±13.83)μg.L-1,P<0.01],平均达峰时间差异无显著性[(2.38±0.35)hvs(2.13±0.35)h,P>0.05],平均消除半衰期延长[(2.71±0.38)hvs(4.43±0.93)h,P<0.01],平均血浆药物浓度—时间曲线下面积增大[(137.32±80.16)h.μg.L-1vs(215.19±113.01)h.μg.L-1,P<0.01],平均驻留时间延长[(4.42±0.22)hvs(6.81±0.75)h,P<0.01]。结论伊曲康唑能明显影响维胺酯的药代动力学参数,提示维胺酯可能部分经CYP3A4酶代谢。因此,在临床上两药合用治疗痤疮的同时,应注意维胺酯的给药剂量。     

Pharmacokinetics of midazolam in CYP3A4- and CYP3A5-genotyped subjects

Objective We investigated whether differences in pharmacokinetics of midazolam, a CYP3A probe, could be demonstrated between subjects with different CYP3A4 and CYP3A5 genotypes.Methods Plasma concentrations of midazolam, and of total (conjugated + unconjugated) 1OH-midazolam, and 4OH-midazolam were measured after the oral administration of 7.5 mg or of 75 µg of midazolam in 21 healthy subjects.Results CYP3A5*7, CYP3A4*1E, CYP3A4*2, CYP3A4*4, CYP3A4*5, CYP3A4*6, CYP3A4*8, CYP3A4*11, CYP3A4*12, CYP3A4*13, CYP3A4*17 and CYP3A4*18 alleles were not identified in the 21 subjects. CYP3A5*3, CYP3A5*6, CYP3A4*1B and CYP3A4*1F alleles were identified in 20, 1, 4 and 2 subjects, respectively. No statistically significant differences were observed for the AUC_inf values between the different genotypes after the 75-µg or the 7.5-mg dose.Conclusion Presently, CYP3A4 and CYP3A5 genotyping methods do not sufficiently reflect the inter-individual variability of CYP3A activity.     

中药止咳橘红颗粒对CYP3A4和CYP1A2抑制作用的研究

目的：在人体内研究止咳橘红对CYP3A4和CYP1A2的抑制作用，以预测止咳橘红与常用临床药物的相互作用。方法：咪哒唑仑和咖啡因分别作为CYP3A4和A2的探针药物，采取交叉设计，10名受试者在服用3d止咳橘红的前后均服用7.5mg咪哒唑仑和100mg咖啡因，服药后采血测定两者及代谢产物的代谢动力学参数，探讨针药物及代谢物的浓度用HPLC-MS法测定，Cmax,tmax从药时曲线中直接读出，AUC用梯形法计算，Ke用3P87程序进行拟合计算，分析服药前后CYP3A4和CYP1A2被抑制的情况，结果 服用止咳橘红后，咪哒唑仑的代谢受到了轻微的抑制，它的血药浓度，达峰时间和药时曲线下面积都有了升高趋势，但无显著差异。而咖啡因的代谢未受到影响。结论 止咳橘红对CYP3A4的活性有较弱的抑制作用，能够导致CYP3A4底物咪哒唑仑代谢的轻微抑制，而对CYP1A2的活性没有影响。止咳橘红长期使用或超过治疗剂量使用时是否会对CYP3A4产生显著性影响。尚需进一步的研究证明。     

The CYP2C8 inhibitor gemfibrozil does not increase the plasma concentrations of zopiclone

Objective Zopiclone is a short acting hypnotic, which is metabolised by cytochrome P450 (CYP) 3A4 and 2C8 in vitro. We studied the possible effect of gemfibrozil, an inhibitor of CYP2C8, on the pharmacokinetics and pharmacodynamics of zopiclone.Methods In a randomised 2-phase crossover study, 10 healthy volunteers took 600 mg gemfibrozil or placebo orally twice daily for 3 days. On day 3, each ingested a 7.5 mg dose of zopiclone. Plasma concentrations and urinary excretion of zopiclone and its two primary metabolites, plasma gemfibrozil, and psychomotor performance were measured. The effects of CYP2C8, CYP2C9 and CYP3A4 inhibitors on the depletion of zopiclone (500 nM) were studied in vitro in human liver microsomes.Results The pharmacokinetic variables of the parent zopiclone were not significantly affected by gemfibrozil. However, gemfibrozil raised the mean peak plasma concentration (C_max) of N-oxide-zopiclone (1.6-fold; P<0.001) and that of N-desmethyl-zopiclone (1.2-fold; P<0.001). The mean area under the plasma concentration-time curve () values of N-oxide-zopiclone and N-desmethyl-zopiclone were raised 2-fold (P<0.001) and 1.2-fold (P<0.01), respectively. The renal clearance of N-oxide-zopiclone was reduced by 48% by gemfibrozil (P<0.001). The pharmacodynamic effects of zopiclone, measured using psychometric tests, were not affected by gemfibrozil. In vitro, ketoconazole (1 μM) and itraconazole (8 μM) decreased the elimination rate of zopiclone enantiomers by about 65–95%, while montelukast (16 μM), gemfibrozil (200 μM) and sulfaphenazole (10 μM) had no appreciable effect.Conclusions Gemfibrozil does not increase the plasma concentrations of the parent zopiclone. Accordingly, CYP2C8 does not significantly metabolise zopiclone in vivo. However, as gemfibrozil raises the concentrations of two potentially active metabolites of zopiclone, slightly enhanced effects of zopiclone by gemfibrozil can not be excluded.