CYP3A activity based on plasma 4β-hydroxycholesterol during the early postpartum period has an effect on the plasma disposition of amlodipine

The utility of endogenous glycochenodeoxycholate-3-sulfate and 4β-hydroxycholesterol to evaluate the hepatic disposition of atorvastatin in rats

The liver is an important organ for drugs disposition, and thus how to accurately evaluate hepatic clearance is essential for proper drug dosing. However, there are many limitations in drug dosage adjustment based on liver function and pharmacogenomic testing. In this study, we evaluated the ability of endogenous glycochenodeoxycholate-3-sulfate (GCDCA-S) and 4β-hydroxycholesterol (4β-HC) plasma levels to evaluate organic anion-transporting polypeptide (Oatps)-mediated hepatic uptake and Cyp3a-meidated metabolism of atorvastatin (ATV) in rats. The concentration of ATV and its metabolites, 2-OH ATV and 4-OH ATV, was markedly increased after a single injection of rifampicin (RIF), an inhibitor of Oatps. Concurrently, plasma GCDCA-S levels were also elevated. After a single injection of the Cyp3a inhibitor ketoconazole (KTZ), plasma ATV concentrations were significantly increased and 2-OH ATV concentrations were decreased, consistent with the metabolism of ATV by Cyp3a. However, plasma 4β-HC was not affected by KTZ treatment despite it being a Cyp3a metabolite of cholesterol. After repeated oral administration of RIF, plasma concentrations of ATV, 2-OH ATV and 4-OH ATV were markedly increased and the hepatic uptake ratio of ATV and GCDCA-S was decreased. KTZ did not affect plasma concentrations of ATV, 2-OH ATV and 4-OH ATV, but significantly decreased the metabolic ratio of total and 4-OH ATV. However, the plasma level and hepatic metabolism of 4β-HC were not changed by KTZ. The inhibition of hepatic uptake of GCDCA-S by RIF was fully reversed after a 7-d washout of RIF. Plasma concentration and hepatic uptake ratio of GCDCA-S were correlated with the plasma level and hepatic uptake of ATV in rats with ANIT-induced liver injury, respectively. These results demonstrate that plasma GCDCA-S is a sensitive probe for the assessment of Oatps-mediated hepatic uptake of ATV. However, Cyp3a-mediated metabolism of ATV was not predicted by plasma 4β-HC levels in rats.

Effects of Danshen tablets on pharmacokinetics of amlodipine in rats

CONTEXT

Danshen tablets (DST), an effective traditional Chinese multi-herbal formula, are often combined with amlodipine (ALDP) for treating coronary heart disease.

OBJECTIVE

This study investigated the effects of DST on the pharmacokinetics of ALDP and the potential mechanism.

MATERIALS AND METHODS

The pharmacokinetics of ALDP (1 mg/kg) in male Sprague-Dawley rats (n = 6), with or without pretreatment of DST (100 mg/kg for 7 d), were investigated using LC-MS/MS. The effects of DST on the metabolic stability of ALDP were also investigated using rat liver microsomes (RLM).

RESULTS

The results indicated that C_max (16.25 ± 2.65 vs. 22.79 ± 2.35 ng/ml), AUC_(0-t) (222.87 ± 59.95 vs. 468.32 ± 69.87 n gh/ml), and t_1/2 (10.60 ± 1.05 vs. 14.15 ± 1.59 h) decreased significantly when DST and ALDP were co-administered, which suggested that DST might influence the pharmacokinetic behaviour of ALDP when they are co-administered. The metabolic stability of ALDP was also decreased (23.6 ± 4.7 vs. 38.9 ± 5.2) with the pretreatment of DST.

DISCUSSION AND CONCLUSIONS

This study indicated that DST could accelerate the metabolism of ALDP in RLM and change the pharmacokinetic behaviours of ALDP. Accordingly, these results showed that the herb-drug interaction between DST and ALDP might occur when they were co-administered. Therefore, the clinical dose of ALDP should be increased when DST and ALDP are co-administered.

Relationships between endogenous CYP3A markers and plasma amlodipine exposure and metabolism in early postpartum and non-peripartum women with hypertension

OBJECTIVE

This study aimed to evaluate the relationship between endogenous CYP3A markers and plasma amlodipine (AML) exposure and metabolism parameters in early postpartum and non-peripartum women.

METHODS

Twenty-four AML-treated early postpartum women with hypertensive disorders of pregnancy and 30 non-peripartum women with essential hypertension were enrolled. Blood samples for determination of CYP3A markers including total cholesterol-adjusted 4β-hydroxycholesterol (4β-OHC/TC), 25-hydroxyvitamin D (25-OHD), and AML and its metabolites in plasma were collected at 24 h after the AML treatment.

RESULTS

The plasma 4β-OHC/TC in postpartum women was higher than that in non-peripartum women, while the plasma 25-OHD was lower. The postpartum women had a lower plasma AML concentration and its metabolic ratio was higher. The plasma 4β-OHC/TC decreased as the number of days post-delivery increased. The plasma AML concentration increased as the number of days post-delivery increased, while the metabolic ratio of AML declined slightly. Tendency toward negative correlations between the plasma 4β-OHC/TC but not 25-OHD, and AML concentration were observed in both postpartum and non-peripartum women. In both groups, the plasma 4β-OHC/TC was correlated with the metabolic ratio of AML.

CONCLUSIONS

The early postpartum women had higher plasma 4β-OHC and AML metabolism. The plasma 4β-OHC had positive relationships with amlodipine metabolism in both women groups. AML metabolism and plasma 4β-OHC may be useful as CYP3A markers in early postpartum and non-peripartum women.

Effects of triptolide on pharmacokinetics of amlodipine in rats by using LC-MS/MS

CONTEXT

Triptolide and amlodipine are often simultaneously used for reducing urine protein excretion after renal transplantation in China clinics.

OBJECTIVE

This study investigated the effects of triptolide on the pharmacokinetics of amlodipine in male Sprague-Dawley rats.

MATERIALS AND METHODS

The pharmacokinetics of amlodipine (1 mg/kg) with or without triptolide pre-treatment (2 mg/kg/day for seven days) were investigated using a sensitive and reliable LC-MS/MS method. Additionally, the inhibitory effects of triptolide on the metabolic stability of amlodipine were investigated using rat liver microsome incubation systems.

RESULTS

The results indicated that when the rats were pre-treated with triptolide, the Cmax of amlodipine increased from 13.78 ± 3.57 to 19.96 ± 4.56 ng/mL (p < 0.05), the Tmax increased from 4.04 ± 1.15 to 5.89 ± 1.64 h (p < 0.05), and the AUC0-t increased by approximately 104% (p < 0.05), which suggested that the pharmacokinetic behaviour of amlodipine was affected after oral co-administration of triptolide. Additionally, the metabolic half-life was prolonged from 22.5 ± 4.26 to 36.8 ± 6.37 min (p < 0.05) with the pre-treatment of triptolide.

CONCLUSIONS

In conclusion, these results indicated that triptolide could affect the pharmacokinetics of amlodipine, possibly by inhibiting the metabolism of amlodipine in rat liver when they are co-administered.

Effect Of epigallocatechin-3-gallate on the pharmacokinetics of amlodipine in rats

This study investigates the effect of epigallocatechin-3-gallate (EGCG), a major ingredient of green tea, on the pharmacokinetics of amlodipine in rats. The pharmacokinetics of orally administered amlodipine (1 mg/kg) with or without EGCG pretreatment (30 mg/kg/day for 10 days) were investigated. Plasma concentrations of amlodipine were determined by using a sensitive and reliable liquid chromatography with tandem mass spectroscopy (LC-MS/MS) method. The effects of EGCG on the metabolic stability of amlodipine were investigated by using rat liver microsome incubation systems. The results indicated that when the rats were pretreated with EGCG, the C_max of amlodipine increased from 16.32 ± 2.57 to 21.44 ± 3.56 ng/mL (p < 0.05), the T_max decreased from 5.98 ± 1.25 to 4.01 ± 1.02 h (p < 0.05), and the AUC_0-t increased from 258.12 ± 76.25 to 383.34 ± 86.95 μg h L^-1 (p < 0.05), which suggested that the pharmacokinetic behavior of amlodipine was affected after oral co-administration of EGCG. Additionally, the metabolic half-life was prolonged from 31.3 ± 5.6 to 52.6 ± 7.9 min (p < 0.05) with the pretreatment of EGCG. It can be speculated that the drug-drug interaction between EGCG and amlodipine might occur, which might have resulted from the metabolism inhibition of amlodipine by EGCG when they were co-administered.