Mass spectrometric characterization of carfentanil metabolism in human, dog, and rat lung microsomes via comparison to chemically synthesized metabolite standards

Gender differences pharmacokinetics, bioavailability, hepatic metabolism and metabolism studies of Pinnatifolone A, a sesquiterpenoid compound, in rats by LC-MS/MS and UHPLC-Q-TOF-MS/MS

BACKGROUND

Pinnatifolone A is a typical sesquiterpenoid and the primary active ingredient of Syringa oblata Lindl., has potent anti-inflammatory activity. However, Pinnatifolone A pharmacokinetic and metabolites analysis investigations in male and female rats, as well as its in vitro stability in male and female rat liver microsomes, have not been evaluated and compared.

PURPOSE

To investigate preclinical pharmacokinetic and metabolite in both genders, confirm gender differences, and provide usable information for the development of clinical applications.

METHODS

A quick, precise, and sensitive LC-MS/MS method was created and effectively used to determine the pharmacokinetics of oral (140 mg/kg) and intravenous (6.3 mg/kg) Pinnatifolone A in male and female rats, in vitro Pinnatifolone A elimination studies in male and female rat liver microsomes. Following that, a UHPLC-Q-TOF-MS/MS technique was established to identify the metabolic profiles of Pinnatifolone A obtained from rat plasma and excreta.

RESULTS

In the current study, we established for the first time an LC-MS/MS method for the quantitation of Pinnatifolone A with acceptable linearity and selectivity, recovery and matrix effect, accuracy and precision. The absolute oral bioavailability of Pinnatifolone A was approximately 30.36% in female rats, the clearance (CL) was 20.99±3.33 l/h/kg in female rats and 472.37±437.31 l/h/kg in male rats. This difference in rat genders may pertain to the sex-specific expression of hepatic enzymes as demonstrated in the metabolic stability evaluation in the present research; the male rats exhibited higher CL_int(mic) (158.83±9.57 μl/min/mg protein) than female rats (76.47±7.90 μl/min/mg protein) liver microsomes, indicating higher Pinnatifolone A clearance in male rats. Twenty-four metabolites were detected and identified in female and male rats; N-acetylcysteine conjugation metabolite was the most abundant metabolites in both rat feces and urine. Furthermore, male and female rats had significantly different levels of the N-acetylcysteine conjugation metabolite. Hydrogenation metabolite was particular to female rats both in rat fecal and urine. Glucuronide conjugation metabolite was the predominant metabolite in rat plasma, and its amount in female rats was double that of male rats.

CONCLUSIONS

The present research is the first to report the preclinical pharmacokinetics and metabolites of Pinnatifolone A in male and female rats, confirming the gender-based differences. The findings provide a comprehensive overview for further understanding of the pharmacokinetic and metabolic characteristics of Pinnatifolone A and serve as a guide for its future development and utilization.

Metabolism of the active carfentanil metabolite, 4-Piperidinecarboxylic acid, 1-(2-hydroxy-2-phenylethyl)-4-[(1-oxopropyl)phenylamino]-, methyl ester in vitro

Carfentanil, a µ-opioid receptor (MOR) agonist with an analgesic potency 10,000 times that of morphine, is extensively metabolized to norcarfentanil (M1), 4-Piperidinecarboxylic acid, 1-(2-hydroxy-2-phenylethyl)-4-[(1-oxopropyl)phenylamino]-, methyl ester (M0 in this article), and other low abundant metabolites in human hepatocytes and liver/lung microsomes. M0 possessed comparable MOR activity to carfentanil, and accounted for approximately 12 % of the total carfentanil metabolite formation in human liver microsomes (HLMs). Little is known about the subsequent elimination of M0. This study investigated its metabolic pathway in HLMs, separation and preliminary identification of metabolites by liquid chromatography-tandem mass spectrometry, and possible involvement of cytochrome P450 enzymes in M0 metabolism with kinetic analysis. M0 produced 9 metabolites via N-dealkylation (M1), oxidation (M3, M6-9), N-dealkylation followed by oxidation (M2 and M4), and glucuronidation (M5). Formation of the major metabolite M1 fitted typical Michaelis-Menten kinetics. Recombinant human CYP3A5 showed the highest activity toward M1 formation followed by CYP3A4 and CYP2C8, while M8 was primarily formed by CYP3A4 followed by CYP2C19 and CYP2C8. These findings reveal the main involvement of CYP3A5 and 3A4 in human hepatic elimination of M0 with a kinetic profile similar to carfentanil which may inform development of treatment protocols for carfentanil exposure.

In Vitro and In Vivo Analysis of Fentanyl and Fentalog Metabolites using Hyphenated Chromatographic Techniques: A Review

Fentanyl and fentanyl analogues (also called fentalogs) are used as medical prescriptions to treat pain for a long time. Apart from their pharmaceutical applications, they are misused immensely, causing the opioid crisis. Fentanyl and its analogues are produced in clandestine laboratories and sold over dark Web markets to different parts of the world, leading to a rise in the death rate due to drug overdose. This is because the users are unaware of the lethal effects of the newer forms of fentalogs. Unlike other drugs, these fentalogs cannot be detected easily, as very little data are available, and this is one of the major reasons for the risk of life-threatening poisoning or deaths. Hence, rigorous studies of these drugs and their possible metabolites are required. It is also necessary to develop techniques for the detection of minute traces of metabolites in biological fluids. This Review provides an overview of the application of hyphenated chromatographic techniques used to analyze multiple novel fentalogs, using in vivo and in vitro methods. The article focuses on the metabolites formed in phase I and phase II processes in biological specimens obtained in recent cases of drug abuse and overdose deaths that could be useful for the detection and differentiation of multiple fentalogs.

Identification of human cytochrome P450 isozymes involved in the oxidative metabolism of carfentanil

Carfentanil is an ultra-potent opioid with an analgesic potency 10,000 times that of morphine but has received little scientific investigation. In the present study, the human cytochrome P450 (CYP) isozymes catalyzing the oxidative metabolism of carfentanil were investigated. Using UHPLC-HRMS, Michaelis-Menten kinetics of formation for three major metabolites norcarfentanil (M1), pharmaceutical active metabolite 4-[(1-oxopropyl)phenylamino]-1-(2-hydroxyl-2-phenylethyl)-4-piperidinecarboxylic acid methyl ester (M11), and 4-[(1-oxopropyl)phenylamino]-1-(2-oxo-2-phenylethyl)-4-piperidinecarboxylic acid methyl ester (M15) were determined. Isozymes catalyzing the formation of the low abundant, highly active metabolite 1-[2-(2-hydroxylphenyl)ethyl]-4-[(1-oxopropyl)phenylamino]-4-piperidinecarboxylic acid methyl ester (M13) were also identified. Selective P450 inhibition studies with pooled human liver microsomes (HLMs) and recombinant CYP isozymes suggested that metabolites M1, M11, and M15 were predominantly formed by isozyme CYP3A5, followed by CYP3A4. Isozymes CYP2C8 and CYP2C9 also made contributions but to a much lesser extent. Highly potent metabolite M13 was predominantly formed by isozyme CYP2C9, followed by CYP2C8. These findings indicate that CYP3A5, CYP3A4, CYP2C8 and CYP2C9 play a major role in the transformation of carfentanil to M1 (norcarfentanil), M11, M13 and M15 through N-dealkylation of piperidine ring, hydroxylation of phenethyl group and ketone formation on phenethyl linker by human liver micrsomes.

Carfentanil - from an animal anesthetic to a deadly illicit drug

The use of novel synthetic opioids as recreational drugs has become a public health concern as they are implicated in numerous fatal intoxications across the world. Synthetic opioids have played a major role in the United States opioid crisis and may contribute to a similar opioid epidemic in Europe. The most prominent group of designer opioids consists of fentanyl and its analogues. At present, carfentanil is the most dangerous fentanyl derivative. It was recently detected as an adulterant to other illicit drugs and counterfeit pharmaceuticals, contributing to life-threatening hospital admissions and fatalities. Toxic exposure to carfentanil typically occurs through injection, insufflation or inhalation. Carfentanil produces similar pharmacotoxicological effects to other opioids. However, due to its extraordinary potency, reversing carfentanil-induced severe and recurring respiratory depression requires administration of multiple or higher than standard doses of naloxone. Toxicological reports indicate that carfentanil use is strongly connected to polydrug use. Detection of carfentanil requires specific and sensitive analytical methods that are not commonly available in hospitals. Since abuse of carfentanil is an emerging problem, particularly in the United States, there is an urgent need to develop new techniques for rapid determination of intoxication evoked by this drug as well as new treatment regimens for effective overdose maintenance. This review presents current knowledge on pharmacological activity of carfentanil, prevalence and patterns of use, and analytical methods of its detection. Special emphasis is given to carfentanil-related non-fatal and lethal overdose cases.

DARK Classics in Chemical Neuroscience: Carfentanil

Because of its remarkable potency and relative ease of synthesis, carfentanil (1) has recently emerged as a problematic contaminant in other drugs of abuse. Carfentanil and its close analogs, currently approved only for large animal veterinary medicine, have found use both as illicit additives to the clandestine manufacture of scheduled drugs and as chemical weapons. In this Review, the background, synthesis, manufacture, metabolism, pharmacology, approved indications, dosage, and adverse effects of carfentanil will be discussed along with its emergence as a key player in the ongoing opioid crisis.