Effects of lovastatin on the pharmacokinetics of nicardipine in rats

Statins Increase the Bioavailability of Fixed-Dose Combination of Sofosbuvir/Ledipasvir by Inhibition of P-glycoprotein

BACKGROUND

Coadministration of statins and direct acting antiviral agents is frequently used. This study explored the effects of both atorvastatin and lovastatin on pharmacokinetics of a fixed-dose combination of sofosbuvir/ledipasvir "FDCSL".

METHODS

12 healthy volunteers participated in a randomized, three-phase crossover trial and were administered a single atorvastatin dose 80 mg plus tablet containing 400/90 mg FDCSL, a single lovastatin dose 40 mg plus tablet containing 400/90 mg FDCSL, or tablets containing 400/90 mg FDCSL alone. Liquid chromatography-tandem mass spectrometry was used to analyze plasma samples of sofosbuvir, ledipasvir and sofosbuvir metabolite "GS-331007" and their pharmacokinetic parameters were determined.

RESULTS

Atorvastatin caused a significant rise in sofosbuvir bioavailability as explained by increasing in AUC0-∞ and Cmax by 34.36% and 11.97%, respectively. In addition, AUC0-∞ and Cmax of GS-331007 were increased by 73.73% and 67.86%, respectively after atorvastatin intake. Similarly, co-administration of lovastatin with FDCSL increased the bioavailability of sofosbuvir, its metabolite (AUC0-∞ increase by 17.2%, 17.38%, respectively, and Cmax increase by 12.03%, 22.24%, respectively). However, neither atorvastatin nor lovastatin showed a change in ledipasvir bioavailability. Hepatic elimination was not affected after statin intake with FDCSL. Compared to lovastatin, atorvastatin showed significant increase in AUC0-∞ and Cmax of both sofosbuvir and its metabolite.

CONCLUSIONS

Both atorvastatin and lovastatin increased AUC of sofosbuvir and its metabolite after concurrent administration with FDCSL. Statins' P-glycoprotein inhibition is the attributed mechanism of interaction. The increase in sofosbuvir bioavailability was more pronounced after atorvastatin intake. Close monitoring is needed after co-administration of atorvastatin and FDCSL.

Evaluation of the Role of P-glycoprotein (P-gp)-Mediated Efflux in the Intestinal Absorption of Common Substrates with Elacridar, a P-gp Inhibitor, in Rats

BACKGROUND AND OBJECTIVES

P-glycoprotein (P-gp) has been shown previously to contribute to the intestinal absorption of verapamil, diltiazem, tacrolimus, colchicine and indinavir in situ; however, its contribution in vivo is unknown. The present study aimed to evaluate the in vivo involvement of P-gp using elacridar as its inhibitor to distinguish the contribution of P-gp from cytochrome P450 (CYP) 3A.

METHODS

Fexofenadine (5 mg/kg) and buspirone (1 mg/kg) were used as probe substrates of P-gp and CYP3A, respectively. Each dual substrate (1 or 2 mg/kg) was orally administered to rats after elacridar pre-treatment (3 mg/kg). Additionally, verapamil, diltiazem or tacrolimus was orally co-administered with fexofenadine.

RESULTS

Elacridar drastically increased the area under the plasma concentration-time curve (AUC_0-t) of oral fexofenadine by 8.6-fold; however, it did not affect the AUC_0-t of oral buspirone. Therefore, elacridar inhibited P-gp without affecting CYP3A. The absorption of oral verapamil, diltiazem and tacrolimus was not influenced by elacridar pre-treatment, and the increase in the AUC_0-t of fexofenadine was approximately 3-fold when co-administered with each substrate; the minimal effect of elacridar was attributable to the limited contribution of P-gp but not to their self-inhibition against the transporter. Conversely, elacridar significantly increased the AUC_0-t of colchicine (5.3-fold) and indinavir (2.0-fold), indicating that P-gp contributes to their absorption.

CONCLUSIONS

Elacridar is useful for distinguishing the contribution of P-gp from CYP3A to the absorption of drugs in rats. The in vivo contribution of P-gp is minimal for high permeable compounds owing to their fraction absorbed of nearly 1.0.

Pharmacokinetic drug-drug interactions between 1,4-dihydropyridine calcium channel blockers and statins: factors determining interaction strength and relevant clinical risk management

Background

Coadministration of 1,4-dihydropyridine calcium channel blockers (DHP-CCBs) with statins (or 3-hydroxy-3-methylglutaryl-coenzyme A [HMG-CoA] reductase inhibitors) is common for patients with hypercholesterolemia and hypertension. To reduce the risk of myopathy, in 2011, the US Food and Drug Administration (FDA) Drug Safety Communication set a new dose limitation for simvastatin, for patients taking simvastatin concomitantly with amlodipine. However, there is no such dose limitation for atorvastatin for patients receiving amlodipine. The combination pill formulation of amlodipine/atorvastatin is available on the market. There been no systematic review of the pharmacokinetic drug–drug interaction (DDI) profile of DHP-CCBs with statins, the underlying mechanisms for DDIs of different degree, or the corresponding management of clinical risk.

Methods

The relevant literature was identified by performing a PubMed search, covering the period from January 1987 to September 2013. Studies in the field of drug metabolism and pharmacokinetics that described DDIs between DHP-CCB and statin or that directly compared the degree of DDIs associated with cytochrome P450 (CYP)3A4-metabolized statins or DHP-CCBs were included. The full text of each article was critically reviewed, and data interpretation was performed.

Results

There were three circumstances related to pharmacokinetic DDIs in the combined use of DHP-CCB and statin: 1) statin is comedicated as the precipitant drug (pravastatin–nimodipine and lovastatin–nicardipine); 2) statin is comedicated as the object drug (isradipine–lovastatin, lacidipine–simvastatin, amlodipine–simvastatin, benidipine-simvastatin, azelnidipine– simvastatin, lercanidipine–simvastatin, and amlodipine–atorvastatin); and 3) mutual interactions (lercanidipine–fluvastatin). Simvastatin has an extensive first-pass effect in the intestinal wall, whereas atorvastatin has a smaller intestinal first-pass effect. The interaction with simvastatin seems mainly driven by CYP3A4 inhibition at the intestinal level, whereas the interaction with atorvastatin is more due to hepatic CYP3A4 inhibition. The interaction of CYP3A4 inhibitor with simvastatin has been more pronounced compared with atorvastatin. From the current data, atorvastatin seems to be a safer CYP3A4-statin for comedication with DHP-CCB. There is no convincing evidence that amlodipine is an unusual DHP-CCB, either as a precipitant drug or as an object drug, from the perspective of CYP3A4-mediated drug metabolism. Amlodipine may have interactions with CYP3A5 in addition to CYP3A4, which may explain its particular characteristics in comparison with other DHP-CCBs. The degree of DDIs between the DHP-CCB and statin and the clinical outcome depends on many factors, such as the kind of statin, physicochemical proprieties of the DHP-CCB, the dose of either the precipitant drug or the object drug, the sex of the patient (eg, isradipine–lovastatin), route of drug administration (eg, oral versus intravenous nicardipine–lovastatin), the administration schedule (eg, nonconcurrent dosing method versus concurrent dosing method), and the pharmacogenetic status (eg, CYP3A5-nonexpressers versus CYP3A5-expressers).

Conclusion

Clinical professionals should enhance risk management regarding the combination use of two classes of drugs by increasing their awareness of the potential changes in therapeutic efficacy and adverse drug reactions, by rationally prescribing alternatives, by paying attention to dose adjustment and the administration schedule, and by review of the appropriateness of physician orders. Further study is needed – the DDIs between DHP-CCBs and statins have not all been studied in humans, from either a pharmacokinetic or a clinical perspective; also, the strength of the different pharmacokinetic interactions of DHP-CCBs with statins should be addressed by systematic investigations.

Effects of pravastatin on the pharmacokinetic parameters of nimodipine after oral and intravenous administration in rats: possible role of CYP3A4 inhibition by pravastatin

Objective:

The aim of this study was to investigate the effects of pravastatin on the pharmacokinetics of nimodipine in rats.

Materials and Methods:

The effect of pravastatin on P-glycoprotein (P-gp) and cytochrome P450 (CYP) 3A4 activity was evaluated. Nimodipine was administered to rats intravenously (3 mg/kg) and orally (12 mg/kg) with pravastatin (0.3 and 1 mg/kg).

Results:

Pravastatin inhibited CYP3A4 enzyme activity in a concentration-dependent manner with a 50% inhibition concentration (IC₅₀) of 14 µM. Compared with the oral control group, the area under the plasma concentration-time curve (AUC_0-∞) of nimodipine was increased significantly. Consequently, the absolute bioavailability (AB) of nimodipine with pravastatin (1 mg/kg) was 31.1%, which was significantly enhanced compared with the oral control group. Moreover, the relative bioavailability (RB) of nimodipine was 1.12- to 1.31-fold greater than that of the control group.

Conclusions:

The enhanced oral bioavailability of nimodipine might be mainly due to inhibition of the CYP3A-mediated metabolism of nimodipine in the small intestine and/or in the liver and due to reduction of the total body clearance rather than both to inhibition of the P-gp efflux transporter in the small intestine and reduction of renal elimination of nimodipine by pravastatin. The increase in the oral bioavailability of nimodipine with pravastatin should be taken into consideration of potential drug interactions between nimodipine and pravastatin.