Drug interaction with P-glycoprotein (P-gp) and breast cancer resistance protein (BCRP) may influence its tissue disposition including blood–brain bar

A simple and rapid ultra-high-performance liquid chromatography (UHPLC) method using UV detection was developed for the simultaneous determination of eight β-lactam antibiotics in human plasma, including four penicillins, amoxicillin (AMX), cloxacillin (CLX), oxacillin (OXA), and piperacillin (PIP), and four cephalosporins, cefazolin (CFZ), cefepime (FEP), cefotaxime (CTX), and ceftazidime (CAZ). One hundred-microliter samples were spiked with thiopental as an internal standard, and proteins were precipitated by acetonitrile containing 0.1% formic acid. Separation was achieved on a pentafluorophenyl (PFP) column with a mobile phase composed of phosphoric acid (10 mM) and acetonitrile in gradient elution mode at a flow rate of 500 μl/min. Detection was performed at 230 nm for AMX, CLX, OXA, and PIP and 260 nm for CFZ, FEP, CTX, and CAZ. The total analysis time did not exceed 13 min. The method was found to be linear at concentrations ranging from 2 to 100 mg/liter for each compound, and all validation parameters fulfilled international requirements. Between- and within-run accuracy errors ranged from −5.2% to 11.4%, and precision was lower than 14.2%. This simple method requires small-volume samples and can easily be implemented in most clinical laboratories to promote the therapeutic drug monitoring of β-lactam antibiotics. The simultaneous determination of several antibiotics considerably reduces the time to results for clinicians, which may improve treatment efficiency, especially in critically ill patients.

Some of the ATP-binding cassette (ABC) transporters like P-glycoprotein (P-gp; ABCB1, MDR1), BCRP (ABCG2) and MRPs (ABCCs) that are present at the blood-brain barrier (BBB) influence the brain pharmacokinetics (PK) of their substrates by restricting their uptake or enhancing their clearance from the brain into the blood, which has consequences for their CNS pharmacodynamics (PD). Opioid drugs have been invaluable tools for understanding the PK-PD relationships of these ABC-transporters. The effects of morphine, methadone and loperamide on the CNS are modulated by P-gp. This review examines the ways in which other opioid drugs and some of their active metabolites interact with ABC transporters and suggests new mechanisms that may be involved in the variability of the response of the CNS to these drugs like carrier-mediated system belonging to the solute carrier (SLC) superfamily. Exposure to opioids may also alter the expression of ABC transporters. P-gp can be overproduced during morphine treatment, suggesting that the drug has a direct or, more likely, an indirect action. Variations in cerebral neurotransmitters during exposure to opioids and the release of cytokines during pain could be new endogenous stimuli affecting transporter synthesis. This review concludes with an analysis of the pharmacotherapeutic and clinical impacts of the interactions between ABC transporters and opioids.

Objectives: Deaths due to asphyxia as well as following acute poisoning with severe respiratory depression have been attributed to buprenorphine in opioid abusers. However, in human and animal studies, buprenorphine exhibited ceiling respiratory effects, whereas its metabolite, norbuprenorphine, was assessed as being a potent respiratory depressor in rodents. Recently, norbuprenorphine, in contrast to buprenorphine, was shown in vitro to be a substrate of human P-glycoprotein, a drug-transporter involved in all steps of pharmacokinetics including transport at the blood–brain barrier. Our objectives were to assess P-glycoprotein involvement in norbuprenorphine transport in vivo and study its role in the modulation of buprenorphine-related respiratory effects in mice. Setting: University-affiliated research laboratory, INSERM U705, Paris, France. Subjects: Wild-type and P-glycoprotein knockout female Friend virus B-type mice. Interventions: Respiratory effects were studied using plethysmography and the P-glycoprotein role at the blood–brain barrier using in situ brain perfusion. Measurements and Main Results: Norbuprenorphine(≥1 mg/kg) and to a lesser extent buprenorphine (≥10 mg/kg) were responsible for dose-dependent respiratory depression combining increased inspiratory (T_I) and expiratory times (T_E). PSC833, a powerful P-glycoprotein inhibitor, significantly enhanced buprenorphine-related effects on T_I (p < .01) and T_E (p < .05) and norbuprenorphine-related effects on minute volume (V_E, p < .05), T_I, and T_E (p < .001). In P-glycoprotein-knockout mice, buprenorphine-related effects on V_E (p < .01), T_E (p < .001), and T_I (p < .05) and norbuprenorphine-related effects on V_E (p < .05) and T_I (p < .001) were significantly enhanced. Plasma norbuprenorphine concentrations were significantly increased in PSC833-treated mice (p < .001), supporting a P-glycoprotein role in norbuprenorphine pharmacokinetics. Brain norbuprenorphine efflux was significantly reduced in PSC833-treated and P-glycoprotein-knockout mice (p < .001), supporting P-glycoprotein-mediated norbuprenorphine transport at the blood–brain barrier. Conclusions: P-glycoprotein plays a key-protective role in buprenorphine-related respiratory effects, by allowing norbuprenorphine efflux at the blood–brain barrier. Our findings suggest a major role for drug–drug interactions that lead to P-glycoprotein inhibition in buprenorphine-associated fatalities and respiratory depression.

The effects of metoclopramide on the central nervous system (CNS) in patients suggest substantial brain distribution. Previous data suggest that metoclopramide brain kinetics may nonetheless be controlled by ATP-binding cassette (ABC) transporters expressed at the BBB blood-brain barrier (BBB). We used ¹¹C-metoclopramide PET imaging to elucidate the kinetic impact of transporter function on metoclopramide exposure to the brain. METHODS: ¹¹C-metoclopramide transport by P-glycoprotein (P-gp, ABCB1) and the Breast Cancer Resistance Protein (BCRP, ABCG2) was tested using uptake assays in cells overexpressing P-gp and BCRP. ¹¹C-metoclopramide brain kinetics were compared using PET in rats (n = 4-5) in the absence and the presence of a pharmacological dose of metoclopramide (3 mg/kg), with or without P-gp inhibition using i.v tariquidar (8 mg/kg). The ¹¹C-metoclopramide brain distribution (V_T, based on Logan plot analysis) and brain kinetics (2-tissue compartment - 2TC model) were characterized with either a measured or an imaged-derived input function. Plasma and brain radiometabolites were studied using radio-HPLC analysis. RESULTS: ¹¹C-metoclopramide transport was selective for P-gp over BCRP. Pharmacological dose did not impact baseline ¹¹C-metoclopramide brain kinetics (V_T=2.28±0.32 and 2.04±0.19 mL.cm^-3 using microdose and pharmacological dose, respectively). Tariquidar significantly enhanced microdose ¹¹C-metoclopramide V_T (7.80±1.43 mL.cm^-3) with a 4.4-fold increase in K₁ and a 2.3-fold fold increase in BP_ND (=k₃/k₄) in the 2TC model. In the pharmacological situation, P-gp inhibition significantly increased metoclopramide brain distribution (V_T =6.28±0.48 mL.cm^-3) with a 2.0-fold increase in K₁ and a 2.2-fold decrease in k₂ with no significant impact on BP_ND. In this situation, only parent ¹¹C-metoclopramide could be detected in the brain of P-gp inhibited rats. CONCLUSION: ¹¹C-metoclopramide benefits from favorable pharmacokinetic properties that offer reliable quantification of P-gp function at the BBB in a pharmacological situation. Using metoclopramide as a model of CNS drug, we demonstrate that P-gp function not only reduces influx but also mediates the efflux from the brain back to the blood compartment with additional impact on brain distribution. This PET-based strategy of P-gp function investigation may provide new insight on the contribution of P-gp to the variability of response to CNS drugs between patients.