Effects of grapefruit juice on pharmacokinetics of atorvastatin and pravastatin in Japanese

AIMS: To investigate the effects of repeated grapefruit juice (GFJ) intake on the pharmacokinetics of atorvastatin and pravastatin in Japanese subjects. METHODS: Two randomized, two-way crossover studies were performed. GFJ or water was given to two groups of 10 subjects each three times daily for 2 days. On the third day, single 10 mg doses of atorvastatin or pravastatin were orally administered with GFJ or water, and an additional 250 ml of GFJ or water was taken before lunch and dinner. Plasma concentrations of atorvastatin and its metabolites were determined over 48 h postdosing and of pravastatin and its metabolites over 24 h postdosing. RESULTS: Compared with in the water group, the AUC(0,48 h) of atorvastatin acid significantly increased by 1.40 fold (95% CI 1.02, 1.92; P < 0.05) when atorvastatin was taken with GFJ. AUC(0,48 h) and C(max) of atorvastatin lactone significantly increased by 1.56 (95% CI 1.33, 1.83; P < 0.001) and 1.29 fold (95% CI 1.09, 1.51; P < 0.01), respectively, when atorvastatin was taken with GFJ. No significant changes were detected in any pravastatin pharmacokinetic parameter examined when pravastatin was taken with GFJ. However, AUC(0,24 h) of pravastatin lactone increased 1.31 fold (95% CI 1.01, 1.71; P < 0.05) with GFJ intake. CONCLUSIONS: GFJ was confirmed to significantly affect the pharmacokinetics of atorvastatin but had little or no effect on those of pravastatin in Japanese subjects.     

Influence of grapefruit juice on pharmacokinetics of triptolide in rats grapefruit juice on the effects of triptolide

1.?Triptolide, a major pharmacological component isolated from Tripterygium wilfordii Hook F (TWHF), is a substrate of both CYP3A4 and P-glycoprotein (P-gp).

2.?This study investigates the effects of GFJ on the pharmacokinetics of triptolide in rats.

3.?The pharmacokinetics of orally administered triptolide with or without GFJ pretreatment were investigated. A mechanistic study was also undertaken using the Caco-2 cell transwell model and rat liver microsomes incubation systems to support the in vivo pharmacokinetic data.

4.?The results indicated that coadministration of GFJ could increase the systemic exposure of triptolide significantly, including area under the curve (828.58?±?79.72 versus 541.53?±?45.23?ng·h/mL) and maximum plasma concentration (273.58?±?27.98 versus 193.67?±?10.08?ng/mL). The apparent permeability of triptolide across the Caco-2 cell transwell model increased significantly with the pretreatment of GFJ (from 1.62?±?0.25?×?10^?6 to 2.51?±?0.41?×?10^?6 cm/s), and the metabolic stability of triptolide was also increased from 32.6?±?5.1 to 52.5?±?7.8?min with the pretreatment of GFJ, and the difference was significant (p?5.?In conclusion, GFJ could increase the systemic exposure of triptolide in rats, when GFJ and triptolide was coadministered, and it might work mainly through increasing the absorption of triptolide by inhibiting P-gp, or through slowing down the metabolism of triptolide in rat liver by inhibiting the activity of CYP3A4.     

Effects of grapefruit juice on the pharmacokinetics of acebutolol

AIMS: We aimed to investigate effects of grapefruit juice on acebutolol pharmacokinetics. METHODS: In a randomized cross-over study, 10 healthy subjects ingested 200 mL grapefruit juice or water three times daily for 3 days and twice on day 4. On day 3, each subject ingested 400 mg acebutolol with grapefruit juice or water. The concentrations of acebutolol and its metabolite diacetolol were measured in plasma and urine up to 33 h. RESULTS: Grapefruit juice decreased the peak plasma concentration (Cmax) of acebutolol by 19% from 872 +/- 207 ng mL(-1) to 706 +/- 140 ng mL(-1) (95% CI on the difference -306, -26.4; P < 0.05), and the area under the concentration time curve (AUC(0-33 h)) by 7%, from 4498 +/- 939 ng mL(-1) h to 4182 +/- 915 ng mL(-1) h (95% CI -609, -23.0; P < 0.05). The half-life (t1/2) of acebutolol prolonged from 4.0 to 5.1 h (P < 0.05). The time to peak concentration and the amount of acebutolol excreted into urine (Ae) were unchanged. The Cmax, AUC(0-33 h), and Ae of diacetolol were decreased by 24% (P < 0.05), 18% (P < 0.05), and 20% (P < 0.01), respectively, by grapefruit juice. CONCLUSION: Grapefruit juice caused a small decrease in the plasma concentrations of acebutolol and diacetolol by interfering with gastrointestinal absorption. The interaction between the grapefruit juice and acebutolol is unlikely to be of clinical significance in most of the patients.     

Effects of regular consumption of grapefruit juice on the pharmacokinetics of simvastatin

AIMS: Simvastatin, a substrate for CYP3A4, is extensively metabolized during the first pass. Our aim was to investigate the effect of regular consumption of grapefruit juice on the pharmacokinetics of simvastatin. METHODS: In a randomized cross-over study with two phases, 10 healthy volunteers ingested grapefruit juice 200 ml or water (control) for 3 days. On day 3, a single 40-mg dose of simvastatin was administered with grapefruit juice 200 ml or water. Plasma concentrations of simvastatin and simvastatin acid were determined up to 24 h. RESULTS: Grapefruit juice increased the area under the plasma concentration-time curves from 0 to 24 h [AUC(0-24)] of simvastatin 3.6-fold (range 1.8-6.0-fold; P < 0.01) and that of simvastatin acid 3.3-fold (range 2.1-5.6-fold; P < 0.01), respectively. The peak concentrations (C(max)) of simvastatin and simvastatin acid were increased 3.9-fold (range 2.3-9.3-fold; P < 0.01) and 4.3-fold (range 2.7-7.9-fold; P < 0.01) by grapefruit juice. CONCLUSIONS: Even one glass of grapefruit juice, taken daily, considerably increases the plasma concentrations of simvastatin and simvastatin acid. Grapefruit juice may increase both the cholesterol-lowering effect and the risk of adverse effects of simvastatin.     

Serum concentrations and clinical effects of atorvastatin in patients taking grapefruit juice daily

AIM

To determine whether customary exposure to grapefruit juice (GFJ) alters serum concentrations, effectiveness, and potential adverse effects of atorvastatin in patients requiring the medication.

METHODS

Patients receiving extended treatment with atorvastatin (10, 20 or 40 mg day⁻¹) at a stable dose received 300 ml day⁻¹ of 100% GFJ for a period of 90 days. One cohort of patients (arm A, n = 60) continued on their current dose of atorvastatin; the second cohort (arm B, n = 70) reduced the daily dose by 50%. Serum atorvastatin, lipid profile, liver functions, and creatine phosphokinase (CPK) were measured at baseline and at 30, 60, and 90 days after starting GFJ.

RESULTS

In Arm A patients, co-ingestion of GFJ significantly elevated serum atorvastatin by 19% to 26% compared with baseline. Changes in lipid profile relative to baseline were negligible. There were no adverse effects on liver function tests or CPK. In arm B patients, serum atorvastatin declined by 12% to 25% compared to baseline, with a small but significant unfavourable effect in serum lipid profile. There were no adverse effects on liver function tests or CPK.

CONCLUSION

In patients on extended stable atorvastatin treatment, addition of daily GFJ in typical quantities slightly elevates serum atorvastatin concentrations, but has no meaningful effect on the serum lipid profile, and causes no detectable adverse liver or muscle effects. Reduction of atorvastatin dosage when moderate amounts of GFJ are co-ingested does not appear to be necessary.     

Effect of grapefruit juice on the disposition of manidipine enantiomers in healthy subjects

AIM: To examine the effect of grapefruit juice, an inhibitor of CYP3A4 in the small intestine, on the disposition of manidipine enantiomers in healthy subjects. METHODS: A randomized cross-over study with at least a 2-week wash-out period was performed. Seven healthy male volunteers received an oral 40-mg dose of racemic manidipine after an overnight fast with either grapefruit juice (GFJ) or water, as a control study. Plasma concentrations of (S)- and (R)-manidipine were monitored up to 10 h after the dosing. RESULTS: The plasma concentrations of (S)-manidipine were significantly higher (P<0.001) than those of (R)-manidipine in the control phase with an S/R ratio for the AUC0-infinity of 1.62 (95% confidence interval 1.52, 1.73). GFJ significantly increased Cmax and AUC0-infinity of (S)-manidipine by 2.4-fold (P<0.01) and 2.3-fold (P<0.01), respectively, and Cmax and AUC0-infinity of (R)-manidipine were increased by 3.4-fold (P<0.01) and 3.0-fold (P<0.01), respectively. There were significant differences (P<0.01) in GFJ-mediated percentage increases in Cmax and AUC0-infinity of (S)-manidipine compared with those of (R)-manidipine. The S/R ratio for AUC0-infinity was significantly decreased from 1.6 to 1.2 during the GFJ phase (P<0.01). CONCLUSION: These results indicate that the stereoselective disposition of manidipine was altered by GFJ, as an inhibitor of CYP3A4. GFJ appears to affect this metabolic disposal of (R)-manidipine to a greater extent than that of (S)-manidipine.     

Inhibition of the CYP3A4-mediated metabolism and P-glycoprotein-mediated transport of the HIV-1 protease inhibitor saquinavir by grapefruit juice components

AIMS: Cytochrome P450 3A4 (CYP3A4) and P-glycoprotein (P-gp) are both expressed in the intestinal mucosa and present a barrier to oral drug delivery. CYP3A4 and P-gp share both overlapping tissue distribution and substrate specificity. Grapefruit juice interactions with CYP3A4 substrates are well documented and occur as a consequence of down regulation of intestinal CYP3A4. The aim of the present study was to screen grapefruit juice components against the CYP3A4-mediated metabolism and P-gp mediated transport of the HIV-1 protease inhibitor saquinavir. METHODS: Five grapefruit juice components: quercetin, naringin, naringenin, 6', 7'-dihydroxybergamottin and bergamottin were screened as potential inhibitors of the metabolism of saquinavir by human liver microsomes. The known CYP3A4 inhibitor ketoconazole was also screened for inhibitory potential. These compounds were also screened as modulators of P-gp activity by assessing the directional transport of saquinavir across Caco-2 cell monolayers which express P-gp. The effect of verapamil, a known modulator of P-gp function, was also determined in these cell lines. RESULTS: On preincubation, 6', 7'-dihydroxybergamottin and bergamottin inhibited the metabolism of saquinavir, with IC50 values of 0.33+/-0.23 muM and 0.74+/-0.13 muM, respectively (n=3). Ketoconazole achieved an IC50 of 0. 55+/-0.12 muM (n=4). The other compounds studied failed to reach IC50 at concentrations of up to 100 muM. The transport of saquinavir in the basolateral-->apical (BL-->AP) direction exceeded that in the apical -->basolateral direction (AP-->BL), with apparent permeability coefficients of 199.2+/-15.8x10-7 cm s-1 and 8.00+/-1. 13x10-7 cm s-1, respectively (n=3) which is indicative of a polarized efflux mechanism. The ratio of BL-->AP/AP-->BL for saquinavir was 25, but in the presence of verapamil and ketoconazole this ratio was reduced to 3.6 and 4.0, respectively (n=3), indicating extensive inhibition of P-gp mediated saquinavir efflux. Of the grapefruit juice components studied only naringin and 6', 7'-dihydroxybergamottin had any appreciable effect, reducing the ratio to 7.6 and 7.1, respectively (n=3); but this was due solely to increased AP-->BL transport. CONCLUSIONS: Grapefruit juice components inhibit CYP3A4-mediated saquinavir metabolism and also modulate, to a limited extent, P-gp mediated saquinavir transport in Caco-2 cell monolayers. The in vivo effects of grapefruit juice coadministration are most likely the result of effects on CYP3A4 (inhibition and down regulation) and only to a minor extent on modulation of P-gp function.     

Grapefruit juice markedly increases the plasma concentrations and antiplatelet effects of ticagrelor in healthy subjects

Aim

This study examined the effects of grapefruit juice on the new P2Y₁₂ inhibitor ticagrelor, which is a substrate of CYP3A4 and P-glycoprotein.

Methods

In a randomized crossover study, 10 healthy volunteers ingested 200 ml of grapefruit juice or water thrice daily for 4 days. On day 3, they ingested a single 90 mg dose of ticagrelor.

Results

Grapefruit juice increased ticagrelor geometric mean peak plasma concentration (C_max) to 165% (95% confidence interval 147, 184%) and area under the concentration–time curve (AUC(0,∞)) to 221% of control (95% confidence interval 200, 245%). The C_max and AUC(0,34 h) (P < 0.05) but not the AUC(0,∞) of the active metabolite C12490XX were decreased significantly. Grapefruit juice had a minor effect on ticagrelor elimination half-life prolonging it from 6.7 to 7.2 h (P = 0.036). In good correlation with the elevated plasma ticagrelor concentrations, grapefruit juice enhanced the antiplatelet effect of ticagrelor, assessed with VerifyNow® and Multiplate® methods, and postponed the recovery of platelet reactivity.

Conclusions

Grapefruit juice increased ticagrelor exposure by more than two-fold, leading to an enhanced and prolonged ticagrelor antiplatelet effect. The grapefruit juice–ticagrelor interaction seems clinically important and indicates the significance of intestinal metabolism to ticagrelor pharmacokinetics.     

Effects of grapefruit juice on the absorption of levothyroxine

AIMS: Our aim was to study the effect of grapefruit juice on the pharmacokinetics of levothyroxine. METHODS: In a randomized cross-over study with two phases, 10 healthy subjects ingested 200 ml grapefruit juice or water (control) three times daily for 2 days. On day 3, a single 600 microg dose of levothyroxine was administered with 200 ml grapefruit juice or water, which was also ingested 1 h before and 1 h after levothyroxine. Serum concentrations of total thyroxine (T4) and thyroid-stimulating hormone (TSH) were measured up to 24 h. RESULTS: Grapefruit juice decreased slightly (11%; P < 0.01) the maximal increase of T4 concentration after ingestion of levothyroxine from 66.4 nmol l(-1) to 59.4 nmol l(-1) (95% CI on the difference -11.3, -2.7). The incremental areas under the serum T4 concentration-time curve (dAUC) during the first 4 and 6 h were also decreased slightly: dAUC(0,4 h) by 13% (P < 0.05), from 195 nmol l(-1) h to 169 nmol l(-1) h (95% CI -51, -1) and dAUC(0,6 h) by 9% (P = 0.085), from 298 nmol l(-1) h to 271 nmol l(-1) h (95% CI -58, 4). The decrease in the serum concentration of TSH (1.25 mU l(-1)) measured 24 h after ingestion of levothyroxine, was not altered by grapefruit juice. CONCLUSIONS: Grapefruit juice may slightly delay the absorption of levothyroxine, but it seems to have only a minor effect on its bioavailability. Accordingly, the clinical relevance of the grapefruit juice-levothyroxine interaction is likely to be small.     

Effect of diclofenac, disulfiram, itraconazole, grapefruit juice and erythromycin on the pharmacokinetics of quinidine

AIMS: In vitro studies suggest that the oxidation of quinidine to 3-hydroxyquinidine is a specific marker reaction for CYP3A4 activity. To assess the possible use of this reaction as an in vivo marker of CYP3A4 activity, we studied the involvement of cytochromes CYP2C9, CYP2E1 and CYP3A4 in the in vivo oxidative metabolism of quinidine. METHODS: An open study of 30 healthy young male volunteers was performed. The pharmacokinetics of a 200 mg single oral dose of quinidine was studied before and during daily administration of 100 mg diclofenac, a CYP2C9 substrate (n=6); 200 mg disulfiram, an inhibitor of CYP2E1 (n=6); 100 mg itraconazole, an inhibitor of CYP3A4 (n=6); 250 ml single strength grapefruit juice twice daily, an inhibitor of CYP3A4 (n=6); 250 mg of erythromycin 4 times daily, an inhibitor of CYP3A4 (n=6). Probes of other enzyme activities, caffeine (CYP1A2), sparteine (CYP2D6), mephenytoin (CYP2C19), tolbutamide (CYP2C9) and cortisol (CYP3A4) were also studied. RESULTS: Concomitant administration of diclofenac reduced the partial clearance of quinidine by N-oxidation by 27%, while no effect was found for other pharmacokinetic parameters of quinidine. Concomitant administration of disulfiram did not alter any of the pharmacokinetic parameters of quinidine. Concomitant administration of itraconazole reduced quinidine total clearance, partial clearance by 3-hydroxylation and partial clearance by N-oxidation by 61, 84 and 73%, respectively. The renal clearance was reduced by 60% and the elimination half-life increased by 35%. Concomitant administration of grapefruit juice reduced the total clearance of quinidine and its partial clearance by 3-hydroxylation and N-oxidation by 15, 19 and 27%, respectively. The elimination half-life of quinidine was increased by 19%. The caffeine metabolic index was reduced by 25%. Concomitant administration of erythromycin reduced the total clearance of quinidine and its partial clearance by 3-hydroxylation and N-oxidation by 34, 50 and 33%, respectively. Cmax was increased by 39%. CONCLUSIONS: The results confirm an important role for CYP3A4 in the oxidation of quinidine in vivo, and this applies particularly to the formation of 3-hydroxyquinidine. While a minor contribution of CYP2C9 to the N-oxidation of quinidine is possible, a major involvement of the CYP2C9 or CYP2E1 enzymes in the oxidation of quinidine in vivo is unlikely.     

The impact of CYP2C8 polymorphism and grapefruit juice on the pharmacokinetics of repaglinide

AIMS: The primary aim of the study was to investigate the possible effect of the CYP2C8*3 allele and of grapefruit juice on the pharmacokinetics of repaglinide. Furthermore, the impact of a single dose of grapefruit juice on the pharmacokinetics of repaglinide in relation to dose. METHODS: Thirty-six healthy male subjects, genotyped for CYP2C8*3 (11 genotyped as CYP2C8*1/*3, one as CYP2C8*3/*3 and 24 as CYP2C8*1/*1), participated in a randomized, cross-over trial. In the two phases, the subjects drank 300 mL water or 300 mL grapefruit juice, in randomized order, 2 h before administration of a single dose of either 0.25 mg or 2 mg repaglinide. RESULTS: Neither the mean AUC(0-infinity) (geometric mean ratio: 1.01; 95% CI: 0.93-1.1, P = 0.88) nor the mean C(max) (geometric mean ratio: 1.05; 95% CI: 0.94-1.2, P = 0.35) of repaglinide were statistically significantly different in the group carrying the CYP2C8*3 mutant allele compared with wild-types. Grapefruit juice caused a 19% decrease in the geometric mean ratio of the 3-hydroxyquinidine to quinidine ratio (difference: 0.81; 95% CI: 0.75-0.87, P < 0.0001), which was used as an index of CYP3A4 activity, and an increase in the mean AUC(0-infinity) of repaglinide (geometric mean ratio: 1.13; 95% CI: 1.04-1.2, P = 0.0048), but had no statistically significant effect on the t(1/2). There was no statistically significant difference in blood glucose concentration in subjects who had or had not ingested grapefruit juice. The effect was more pronounced at the low dose of repaglinide (0.25 mg) than at the therapeutic dose of 2 mg. CONCLUSIONS: The pharmacokinetics of repaglinide in subjects carrying the CYP2C8*3 mutant allele did not differ significantly from those in the wild-types. Grapefruit juice increased the bioavailability of repaglinide, suggesting significant intestinal elimination of the drug which was assumed to be primarily mediated by CYP3A4 in the gut.     

Formation of omeprazole sulphone but not 5-hydroxyomeprazole is inhibited by grapefruit juice

AIMS: To determine the effect of grapefruit juice on omeprazole metabolism in vivo. METHODS: This was a randomized crossover study with a 2 week washout period. Omeprazole (20 mg) was taken orally by 13 healthy volunteers after an overnight fast with either grapefruit juice or water. Serial blood samples were obtained over 12 h and standardized meals were served 3 and 10 h after the administration of omeprazole. Plasma concentrations of omeprazole and its major metabolites, 5-hydroxyomeprazole and omeprazole sulphone, were determined by high performance liquid chromatography (h.p.l.c.). RESULTS: Mean area under the plasma concentration vs time curve (AUC) between 0 and 12 h for omeprazole sulphone was approximately 20% lower (P<0.01) in the group receiving grapefruit juice. There was no significant difference in the mean AUC of 5-hydroxyomeprazole or omeprazole. The AUC ratio of omeprazole sulphone to omeprazole, an index of CYP3A4 activity, was decreased by 33% (P<0.001) after administration of grapefruit juice whereas the AUC ratio of 5-hydroxyomeprazole to omeprazole, an index of CYP2C19 activity, did not differ between the two phases of the study. Although the time to peak concentration (tmax ) and terminal half-life (t1/2,z) of omeprazole and its two main metabolites were not altered, the peak concentration (Cmax ) of omeprazole sulphone was significantly reduced after administration of grapefruit juice. CONCLUSION: Administration of grapefruit juice decreased the formation of omeprazole sulphone but not 5-hydroxyomeprazole. These results indicate that activities of CYP3A4, but not of CYP2C19, are inhibited by the simultaneous administration of grapefruit juice.     

Effects of clarithromycin and grapefruit juice on the pharmacokinetics of glibenclamide

AIMS: Case reports suggest that clarithromycin can increase the glucose-lowering effect of glibenclamide which is metabolized mainly by CYP2C9 and is a substrate for P-glycoprotein and OATP2B1. Our objective was to evaluate whether the P-glycoprotein inhibitor, clarithromycin, increases and the putative OATP2B1 inhibitor, grapefruit juice, decreases plasma concentrations of glibenclamide. METHODS: In a randomized three-phase crossover study, 12 subjects ingested 250 mg clarithromycin or placebo twice daily or 200 ml grapefruit juice three times daily for 2 days. On day 3, they ingested 0.875 mg glibenclamide with sugar water or grapefruit juice. Concentrations of glibenclamide and clarithromycin in plasma, glucose in blood, and excretion of hydroxy-glibenclamide into urine were measured up to 12 h. RESULTS: Clarithromycin increased the peak concentration (C(max)) of glibenclamide to 1.25-fold (95% confidence interval (CI) 1.12, 1.40; P < 0.01) and the area under the plasma concentration-time curve to 1.35-fold (95% CI 1.21, 1.50; P < 0.01) compared with the placebo phase. The time to C(max), the half-life of glibenclamide, and the amount of hydroxy-glibenclamide excreted into urine remained unaltered. Grapefruit juice did not change the pharmacokinetics of glibenclamide. Clarithromycin concentrations implied a good compliance. Blood glucose did not deviate between the phases. CONCLUSIONS: Clarithromycin increased plasma concentrations of glibenclamide, possibly by inhibiting P-glycoprotein in the intestinal wall. Although not seen with the present study design, clarithromycin may enhance the effect of glibenclamide by increasing plasma glibenclamide concentrations, which warrants close monitoring of blood glucose during their co-administration. Grapefruit juice had no effect on glibenclamide pharmacokinetics.     

Prediction of the extent and variation of grapefruit juice–drug interactions from the pharmacokinetic profile in the absence of grapefruit juice

The aim of this study was to develop a method for predicting the extent of grapefruit juice (GFJ)–drug interactions and their interindividual variations from the pharmacokinetic profile in the absence of GFJ. The pharmacokinetic profiles of 13 drugs after intravenous and oral administration were used to develop and validate the method. For each drug, the proportion absorbed into the intestine and the intestinal availability (F_g) were calculated from clinical data taken from the literature. Then, the AUC ratio (the ratio of the AUC with GFJ to that without GFJ) was predicted by assuming that F_g was 1.0 when GFJ was concomitantly ingested. According to the developed method, the AUC ratio of felodipine was 2.50 and its coefficient of variation (CV) was 45%, which agreed well with the observed AUC ratio of 2.48 and CV of 51%. Although the developed method overestimated the AUC ratios of some drugs such as nisoldipine, no underestimation occurred. The predicted CV values were consistent with those observed. The developed method might be useful to predict the AUC ratio, along with its interindividual variation, from the pharmacokinetic profile in the absence of grapefruit juice. Copyright © 2014 John Wiley & Sons, Ltd.     

葡萄柚汁与药物的相互作用

目的：了解葡萄柚汁对其他药物代谢的影响及合用后的相互作用。方法：通过对近几年来的国内外文献报道进行收集，归纳，分析，加以综述。结果：葡萄柚汁可改变许多药物的药动学，使血药浓度升高，引起有临床意义的食物－药物相互作用。结论：临床上应尽量避免葡萄柚汁与易受影响的药物，如二氢吡啶类钙拮抗剂，免疫抑制剂，许多中枢神经系统药物，他汀类药物，促胃肠动力药沙必利，HIV蛋白酶抑制剂等合用，以确保用药安全。     

Lack of effect of grapefruit juice on the pharmacokinetics and pharmacodynamics of amlodipine

AIMS: To determine whether repeated once daily administration of grapefruit juice altered the pharmacokinetics or pharmacodynamics of the calcium antagonist amlodipine. METHOD:S The effects of grapefruit juice on the pharmacokinetics and pharmacodynamics of oral and intravenous amlodipine were assessed in 20 healthy men in a placebo-controlled, open, randomized, four-way crossover study using single doses of amlodipine 10 mg. For 9 days beginning with the day of administration of amlodipine, grapefruit juice (or water control) was given once daily, and blood samples, blood pressure and heart rate measures were obtained. Plasma concentrations of amlodipine and its enantiomers were determined in separate assays by GC-ECD. RESULTS: Oral amlodipine had high systemic availability (grapefruit juice: 88%; water: 81%). Pharmacokinetic parameters of racemic amlodipine (AUC, Cmax, tmax, and kel) were not markedly changed with grapefruit juice coadministration. Total plasma clearance and volume of distribution, calculated after intravenous amlodipine, were essentially unchanged by grapefruit juice (CL 6.65 ml min-1 kg-1, juice vs 6.93 ml min-1 kg-1, water; Vdss 22.7 l kg-1, juice vs 21.0 l kg-1, water). Grapefruit juice coadministration did not greatly alter the stereoselectivity in amlodipine oral or intravenous kinetics. The sum of S(-) and R(+) enantiomer concentrations correlated well with total racemic amlodipine concentration (r2 = 0. 957; P = 0.0001). Coadministration of grapefruit juice with either route of amlodipine administration did not significantly alter blood pressure changes vs control. CONCLUSIONS: Grapefruit juice has no appreciable effect on amlodipine pharmacodynamics or pharmacokinetics, including its stereoselective kinetics. Bioavailability enhancement by grapefruit juice, noted with other dihydropyridine calcium antagonists, does not occur with amlodipine. Once daily grapefruit juice administration with usual oral doses of amlodipine is unlikely to alter the profile of response in clinical practice.     

Inhibition of cytochrome P450 by furanocoumarins in grapefruit juice and herbal medicines

INTRODUCTIONFuranocoumarins are minor constituents in plants,belonging to Umbelliferae, Rutaceae, Moraceae, andLeguminosae. Some naturally occurring methoxy de-rivatives of furanocoumarins have been applied clinically,coupled with sunbathing, to cure dermatological dis-eases for more than 2000 years, and their confirmedphotosensitizing properties have led to the developmentof a modern medical principle, photochemotherapy[1].On the other hand, some plants containing furano-coumarins are …     

葡萄柚汁与钙通道阻滞药的相互作用

葡萄柚汁是果汁饮品的主要成分之一,钙通道阻滞药(CCB)是广泛用于高血压等心、脑血管疾病治疗的药物,研究证实两者合用时可能影响CCB的吸收与代谢,改变其药动学参数,并导致不良反应,其中尼卡地平、非洛地平、尼群地平等生物利用度较低,尤应引起关注。葡萄柚汁和CCB相互作用机制可能与葡萄柚汁抑制细胞色素P450 3A4(CYP3A4)活性、提高P-糖蛋白(P-gp)底物转运,而CCB则是CYP3A4和P-gp的底物有关。本文对近年来葡萄柚汁与CCB的食品-药物相互作用的研究进展做一综述。     

Effect of atorvastatin on the intravenous and oral pharmacokinetics of verapamil in rats

The present study aimed to investigate the effect of atorvastatin on the intravenous and oral pharmacokinetics of verapamil in rats. The pharmacokinetic parameters of verapamil were measured after an oral (9 mg/kg) or intravenous (3 mg/kg) administration of verapamil to rats in the presence and absence of atorvastatin. Compared with the control given verapamil alone, the concurrent use of 1.5 mg/kg of atorvastatin significantly increased the oral exposure of verapamil in rats. The AUC and C(max) of verapamil increased by 70% and 61%, respectively in the presence of atorvastatin (1.5 mg/kg), while there was no significant change in T(max) and the terminal plasma half-life (T(1/2)) of verapamil. Accordingly, the presence of atorvastatin significantly (p<0.05) increased the bioavailability of verapamil in rats. In contrast, atorvastatin had no effect on any pharmacokinetic parameters of verapamil given intravenously, implying that atorvastatin may improve the oral bioavailability of verapamil by reducing the prehepatic extraction of verapamil most likely mediated by P-gp and/or CYP3A4. In conclusion, coadministration of atorvastatin significantly enhanced the oral exposure of verapamil in rats without a change in the systemic clearance of intravenous verapamil, suggesting a potential drug interaction between verapamil and atorvastatin via the modulation of prehepatic extraction.     

Interaction between grapefruit juice and hypnotic drugs: comparison of triazolam and quazepam

Objective: Grapefruit juice (GFJ) inhibits cytochrome P450 (CYP) 3A4 in the gut wall and increases blood concentrations of CYP3A4 substrates by the enhancement of oral bioavailability. The effects of GFJ on two benzodiazepine hypnotics, triazolam (metabolized by CYP3A4) and quazepam (metabolized by CYP3A4 and CYP2C9), were determined in this study. Methods: The study consisted of four separate trials in which nine healthy subjects were administered 0.25 mg triazolam or 15 mg quazepam, with or without GFJ. Each trial was performed using an open, randomized, cross-over design with an interval of more than 2 weeks between trials. Blood samples were obtained during the 24-h period immediately following the administration of each dose. Pharmacodynamic effects were determined by the digit symbol substitution test (DSST) and utilizing a visual analog scale. Results GFJ increased the plasma concentrations of both triazolam and quazepam and of the active metabolite of quazepam, 2-oxoquazepam. The area under the curve (AUC)(0–24) of triazolam significantly increased by 96% (p<0.05). The AUC(0–24) of quazepam (+38%) and 2-oxoquazepam (+28%) also increased; however, these increases were not significantly different from those of triazolam. GFJ deteriorated the performance of the subjects in the DSST after the triazolam dose (−11 digits at 2 h after the dose, p<0.05), but not after the quazepam dose. Triazolam and quazepam produced similar sedative-like effects, none of which were enhanced by GFJ. Conclusion These results suggest that the effects of GFJ on the pharmacodynamics of triazolam are greater than those on quazepam. These GFJ-related different effects are partly explained by the fact that triazolam is presystemically metabolized by CYP3A4, while quazepam is presystemically metabolized by CYP3A4 and CYP2C9.