Characterization of amiodarone metabolites and impurities using liquid chromatography/atmospheric pressure chemical ionization mass spectrometry

Imaging drugs, metabolites and biomarkers in rodent lung: a DESI MS strategy for the evaluation of drug-induced lipidosis

Within drug development and pre-clinical trials, a common, significant and poorly understood event is the development of drug-induced lipidosis in tissues and cells. In this manuscript, we describe a mass spectrometry imaging strategy, involving repeated analysis of tissue sections by DESI MS, in positive and negative polarities, using MS and MS/MS modes. We present results of the detected distributions of the administered drug, drug metabolites, lipid molecules and a putative marker of lipidosis, di-docosahexaenoyl (22:6)-bis(monoacylglycerol) phosphate (di-22:6-BMP). A range of strategies have previously been reported for detection, isolation and identification of this compound, which is an isomer of di-docosahexaenoic (22:6 n-3) phosphatidylglycerol (di-22:6 PG), a commonly found lipid that acts as a surfactant in lung tissues. We show that MS imaging using MS/MS can be used to differentiate these compounds of identical mass, based upon the different distributions of abundant fragment ions. Registration of images of these fragments, and detected drugs and metabolites, is presented as a new method for studying drug-induced lipidosis in tissues. Graphical abstract.

The role of CYP 3A4 and 1A1 in amiodarone-induced hepatocellular toxicity

Amiodarone is a widely used potent antiarrhythmic for the treatment of cardiac disease; however, its use is often discontinued due to numerous adverse effects, including hepatotoxicity. To investigate the role of drug metabolism in this liver toxicity, amiodarone and its major metabolite desethylamiodarone were incubated with HepG2 cells overexpressing a series of cytochrome P450 (CYP) isoforms. Significantly higher cytotoxicity of amiodarone was observed in HepG2 cells overexpressing CYP3A4 or CYP1A1, compared with that observed in empty vector transduced control cells. Further, higher levels of the more potent hepatotoxic metabolite desethylamiodarone were detected in CYP3A4 or CYP1A1 expressed cells. The CYP3A4 inhibitor ketoconazole and the CYP1A1 inhibitor α-naphthoflavone drastically inhibited the metabolism of amiodarone to desethylamiodarone. Along with the inhibition of CYP1A1 or CYP3A4, the cytotoxicity of amiodarone was significantly reduced. These data indicate that the metabolism of amiodarone to desethylamiodarone by CYP1A1 or CYP3A4 plays an important role in the hepatocellular toxicity of amiodarone.

Metabolite identification studies on amiodarone in in vitro (rat liver microsomes, rat and human liver S9 fractions) and in vivo (rat feces, urine, plasma) matrices by using liquid chromatography with high-resolution mass spectrometry and multiple-stage mass spectrometry: characterization of the diquinone metabolite supposedly responsible for the drug's hepatotoxicity

RATIONALE

Several mechanisms have been anticipated for the toxicity of amiodarone, such as oxidative stress, lipid peroxidation, phospholipidosis, free radical generation, etc. Amiodarone is structurally similar to benzbromarone, an uricosuric agent, which was withdrawn from European markets due to its idiosyncratic hepatotoxicity. A proposed reason behind the toxicity of benzbromarone was the production of a reactive ortho-diquinone metabolite, which was found to form adducts with glutathione. Therefore, taking a clue that a similar diquinone metabolite of amiodarone may be the reason for its hepatotoxicity, metabolite identification studies were carried out on the drug using liquid chromatography/mass spectrometry (LC/MS) tools.

METHODS

The studies involved in vitro (rat liver microsomes, rat liver S9 fraction, human liver S9 fraction) and in vivo (rat feces, urine, plasma) models, wherein the samples were analyzed by employing LC/HRMS, LC/MS(n) and HDE-MS.

RESULTS AND CONCLUSIONS

A total of 26 metabolites of amiodarone were detected in the investigated in vitro and in vivo matrices. The suspected ortho-diquinone metabolite was one of them. The formation of the same might be an added reason for the hepatotoxicity shown by the drug.

Tubulin-Binding Drug Screening by MALDI-TOFMS

Despite a large amount of drugs available to treat cancer, none is totally satisfactory with respect to its tolerance or side effects. It is very important to discover new compounds that exhibit specific features such as binding to proteic targets. Given the clinical successes of the poisons of the mitotic spindle chemotherapeutic agent class, it is often considered that tubulin represents one of the best cancer targets identified so far, and it seems likely that discovering new drugs of this class will significantly improve the range of active chemotherapeutic agents. The aim of this work is to present the new screening test that has been developed in our laboratory in order to study the binding of compounds to tubulin. We have developed a screening protocol involving three sampling strategies before the MALDI-TOFMS analysis. The three strategies give very accurate and reproducible results and could therefore possibly be used in screening campaigns. We have also proved that no unspecific binding can provide a loss of specificity of the test. Our protocol presents all the requirements for being a useful tool to screen the binding of compounds to tubulin.

Pharmacokinetics of Amiodarone in hyperlipidemic and simulated high fat-meal rat models

The objective of this study was to examine the effect of a high fat meal and hyperlipidemia on the pharmacokinetic behavior of amiodarone. To evaluate these effects, single doses of amiodarone were administered to rats i.v. (25 mg/kg) or orally (50 mg/kg). Some rats were rendered hyperlipidemic by intraperitoneal doses of poloxamer 407 followed by amiodarone i.v. In other normolipidemic rats, amiodarone was administered i.v. in a fasted state or after the administration of 1% cholesterol in peanut oil. Amiodarone plasma concentrations were considerably (>11-fold) increased in hyperlipidemia. Substantial decreases were noted in the clearance, volume of distribution and unbound fraction (11.6, 23 and 24.7-fold, respectively) in plasma of hyperlipidemic rats. Oral lipid caused a significant increase in plasma AUC(0-infinity) (1.38-fold) and a significant decrease in clearance (1.5-fold) of amiodarone after intravenous doses. Oral consumption of 1% cholesterol in peanut oil significantly increased the plasma AUC (1.83-fold) and bioavailability of amiodarone (1.31-fold) after oral doses. In determining oral bioavailability of lipophilic drugs such as amiodarone in food effect studies, in addition to the increase in absorption of drugs, other factors such as a decrease in clearance due to increases in lipoprotein levels should be taken into account.

A quantitative method for the determination of amphiphilic drug release kinetics from nanoparticles using a Langmuir balance

Amiodarone is a drug that is widely used in the treatment of heart disease. To circumvent side effects, colloidal drug carriers have been designed to deliver the drug specifically to the site of action. For the purposes of in vitro characterization of such particles, difficult test systems are employed that usually require the quantitative separation of the drug carrier from the release medium before analysis. In this work, a Langmuir balance was used to characterize amiodarone release. Drug-loaded nanoparticles were prepared from a biodegradable polyester and assayed for their drug release kinetics. Simultaneously, nanoparticles were analyzed for their drug release by a standard procedure based on dialysis tubes combined with high-performance, liquid chromatography. The results obtained by the Langmuir balance experiments were compared with those obtained from high-performance liquid chromatography and were found to correlate well. The interexperimental variation was 4.4% for the Langmuir method (n = 4), and the interexperimental variation for HPLC was 2.9% (n = 3). The major advantage of this new method is the possibility diminishing significantly the required sample amount for the experiment, allowing drug detection in the lower nanomolar range. Moreover, the avoidance of prior nanoparticle separation from the release medium provides important progress of this technique. The Langmuir balance has proven its adaptability as a new sensitive tool for the characterization of amphiphilic drug release kinetics.