20-Week intramuscular toxicity study of rotigotine behenate extended-release microspheres for injection via intramuscular injection in cynomolgus monkeys.

Continuous dopaminergic stimulation (CDS) has become an important strategy for the development of drugs to treat Parkinson's disease (PD). Rotigotine behenate extended-release microspheres (RBEM) for injection represents a new treatment regime for CDS and is being applied for clinical trial. Our study in cynomolgus monkeys was a 20-week repeat dose toxicity investigation with RBEM at dosages of 90, 180, 360, with a 12-week recovery period. The results observed some irritations in the application site and surrounding tissues in Placebo microspheres and each dose of RBEM, was accompanied with increased white blood count and fibrinogen. RBEM-treated monkeys were additionally noted with a pharmacological action-related decrease in prolactin. These findings showed certain reversibility after the 12-week recovery phase. No clear sex difference was noted in the plasma exposure to rotigotine. The exposure generally increased in a dose-proportional manner. In summary, major toxicological effects are associated with the dopamine agonist-related properties of rotigotine, and the removal of foreign bodies caused by p oly (lactide-co-glycolide) (PLGA)and sodium carboxymethyl cellulose (SCMC), and the no-observed-adverse-effect-level (NOAEL) was 360 mg/kg.

Development and validation of an HILIC/MS/MS method for determination of nusinersen in rabbit plasma.

A hydrophilic interaction liquid chromatography tandem mass spectrometry (HILIC/MS/MS) method was developed and validated for the quantitative analysis of the fully phosphorothioate modified oligonucleotide nusinersen. HILIC/MS/MS method is more robust and compatible with mass spectrometry than ion pair reversed-phase liquid chromatography-tandem mass spectrometry (IP-RP-LC/MS/MS). Various types and concentrations of additives and different pH of mobile phase affected the mass spectrometry response, chromatographic peak shape and retention of nusinersen. The optimized extraction method of nusinersen employs hydrophilic-lipophilic balance solid phase extraction, with a recovery of up to 80 %. Chromatographic quantification was performed using a gradient system on an amide column and the mobile phase consisted of ammonium acetate, acetonitrile and water in a certain proportion. The fully phosphorothioate modified nusinersen can obtain a high mass spectrometry response by providing greater peak symmetry and high ionization efficiency in a high-pH mobile phase. Moreover, the significant carry over interference was observed at the pH 6.3 of the mobile phase. Adjusting the pH value up to 10, and the carry over interference disappeared. The lower limit of quantitation of this developed HILIC/MS/MS assay was 30.0 ng/mL and the method was systematic methodology validated. This HILIC/MS/MS method provides an attractive and robust alternative for the quantitative analysis of nusinersen and was applied in the pharmacokinetic study of nusinersen in rabbits.

Exosome-mediated delivery platform of biomacromolecules into the brain: Cetuximab in combination with doxorubicin for glioblastoma therapy.

Monoclonal antibodies (mAbs) have become the predominant treatment modality for various diseases due to their high affinity and specificity. Although antibodies also have great potential for neurological diseases, they couldn't fully meet the therapeutic requirements due to their high molecular weight and limitations in crossing the blood-brain barrier (BBB). Herein, an innovative strategy based on exosomes (Exos) platform was developed to enhance the delivery of cetuximab (CTX) into the brain, and in combination with doxorubicin (DOX) for the synergistic targeted therapy of glioblastoma (GBM). The in vitro/vivo experiments have shown that exosomes could effectively promote BBB penetration and increase the content of CTX in glioma cells and brain lesions. Cytotoxicity and wound healing experiments have shown that CTX-Exo-DOX could significantly inhibit the proliferation of tumor cells. Finally, in vivo results showed that CTX-Exo-DOX significantly prolonged the survival time of tumor-bearing rats to 28 days, which was 1.47 times that of the DOX group. In summary, exosomes could deliver more antibodies into the brain, and CTX-Exo-DOX is a promising co-delivery system for the treatment of GBM. The results of this study will also provide a prospective strategy for antibody drugs in the treatment of neurological diseases.

Carbon fiber-sampling combined flame ionization mass spectrometry for direct analysis of drugs in oral fluid.

Drug-impaired driving poses a significant risk of collisions and other hazardous accidents, emphasizing the urgent need for simple and rapid roadside detection methods. Oral fluid, as an easily collectible and non-invasive test material, has gained widespread use in detecting drug-impaired driving. In this study, we have devised a method for direct sampling using a carbon fiber bundle combined with flame ionization mass spectrometry. The essence of this method lies in the synergy between the adsorption properties of carbon fiber and the plasma characteristics of the flame. Leveraging the strong adsorption capabilities of the carbon fiber bundle allows for the use of a minimal sample size (<100 µL) during sampling, presenting a distinct advantage in the roadside inspection and sampling process. Throughout the flame ionization process, proteins and salts within the oral fluid matrix adhere well to the carbon fiber bundle, while small molecule targets can be efficiently desorbed and react with charged species in the flame, leading to ionization. The results demonstrate the successful development of carbon fiber-sampling combined flame ionization mass spectrometry, capable of qualitative and quantitative analysis of drugs in oral fluid without the need for sample pre-treatment. Its quantitative capabilities are sufficient for real sample detection, providing an effective analytical method for the roadside detection of drugs in oral fluids.

Development, validation and application of an ion-pair reversed-phase liquid chromatography-tandem mass spectrometry method for the quantification of nusinersen.

Background: The fully phosphorothioate-modified oligonucleotide (OGN) nusinersen has low ionization efficiency in the negative ion mode, resulting in a low mass spectrometry response. There have been no relevant reports on developing a LC-MS method for the determination of nusinersen by optimizing mobile phase composition. Materials & methods: Mobile phase additives comprised of 15 mM triethylamine/25 mM 1,1,1,3,3,3-hexafluoro-2-propanol with a pH of 9.6. Nusinersen was extracted from plasma using Oasis® HLB solid-phase extraction (Waters, MA, USA). Results & conclusion: By adjusting the pH of the mobile phase to 9.6 by optimizing the type and concentration of ion-pair reagents, a high mass spectrometry response was obtained. The developed method was applied to nusinersen and met the requirements for the pharmacokinetic study of nusinersen in rabbits.

Population Pharmacokinetic Analysis to Support and Facilitate Switching from Risperidone Formulations to Rykindo in Patients with Schizophrenia.

INTRODUCTION: RYKINDO® (Rykindo) is a novel, long-acting injectable risperidone formulation administered biweekly (Q2W) through intramuscular gluteal injection for the treatment of schizophrenia in adult patients. This analysis was conducted to demonstrate that the clinical outcomes of Rykindo are equivalent to those of RISPERDAL CONSTA® (Consta; Q2W), and to establish a dosing methodology to switch from Consta to Rykindo, as well as to introduce Rykindo to patients who are currently on oral RISPERDAL® (Risperdal). METHODS: Population pharmacokinetic (PK) models for Rykindo and Consta were developed using a nonlinear mixed-effects model with the data from phase 1 studies. A model-based simulation was also conducted using NONMEM. RESULTS: The PK profiles of Rykindo and Consta were adequately represented by a one-compartment model with an immediate release followed by an intermediate and third main release. Drug release of Rykindo was faster than for Consta, reaching steady state approximately 2-3 weeks earlier. The exposures of the active moiety of Rykindo and Consta were comparable at steady state. Model-based simulation indicated that switching from Consta to Rykindo requires administration of the first Rykindo injection within 4-5 weeks following the last Consta injection. For patients taking Risperdal, introducing Rykindo with 1 week of Risperdal supplemental for once-daily dosing (QD) can achieve comparable or superior exposure to that of Consta with 3 weeks of oral QD supplements. A dosing window of ± 3 days for Rykindo was recommended. CONCLUSIONS: This established approach provides guidance to physicians to initiate Rykindo therapy in adult patients with schizophrenia. TRIAL REGISTRATION: ClinicalTrials.gov identifier, NCT02055287, NCT02186769 and NCT02091388.

Facile fluorescence detection of malachite green in fish using molecularly imprinted polymers doped CdTe quantum dots based system.

Malachite green (MG) possesses high toxicity, therefore, the detection of MG in fish tissues is of vital importance. A novel core-shell MIPs doped CdTe quantum dots coated silica nanoparticles (CdTe-MIP/SiO2 NPs) were synthesized via a simple one-pot strategy. The materials were characterized carefully. The resulting CdTe-MIP/SiO2 NPs were coated on the thin layer chromatography plate, and coupled with miniaturized fluorimeter for fluorescence detection of MG in fish samples. The resulting CdTe-MIP/SiO2 NPs based system possessed good linearity (0.01 âˆ¼ 20 µmol/L), high recoveries (98.36 %∼101.45 %) and low detection limit (3.7 nmol/L) for MG. Furthermore, CdTe-MIP/SiO2 NPs based system were employed to measure fish samples spiked with MG, meanwhile, HPLC was utilized to evaluate the accuracy and reliability. And the paired t-test was conducted to evaluate differences between fluorescence method and HPLC, P > 0.05 means no significant difference was observed, the results demonstrated that both fluorescence method and HPLC are suitable for MG analysis.

Population pharmacokinetics of rotigotine extended-release microspheres for intramuscular injection in patients with early-stage Parkinson's disease.

AIMS: Rotigotine extended-release microspheres is a weekly intramuscular injection formulation to treat Parkinson's disease. This study aimed to develop a population pharmacokinetics (PK) model for rotigotine extended-release microspheres to investigate its PK ethnic differences. METHODS: Data for the study were obtained from three studies in China, Japan and the US. The population PK model was developed using the Phoenix NLME 8.3.5 software. Two parallel absorption models were created to include both zero- and first-order absorptions. The elimination phase was evaluated for one- and two-compartment linear models. Moreover, covariates including sex, body weight, body mass index, albumin, creatinine clearance and race were input into the model using a stepwise covariate method. RESULTS: We constructed a one-compartment linear model with the first parallel absorption model identified as the best-fitting model. Simulation results in patients with lighter body weight (45 kg) exhibited a 27% increase in Cmax,ss and a 31% increase in AUCtau,ss compared to those with median body weight (65 kg). Patients with heavier body weight (103 kg) showed a 27% decrease in Cmax,ss and a 29% decrease in AUCtau,ss compared to the median body weight group. Asian patients displayed only a 21% increase in Cmax,ss and a 6% increase in AUCtau,ss compared to non-Asian. While we could not fully conclude that race does not affect rotigotine exposure, dosage adjustments based on race were not deemed necessary. CONCLUSIONS: Exposure differences were mainly attributed to body weight, while dose adjustments were not needed for patients of different racial identities.

A study of the genotoxicity, fertility and early embryonic development toxicity of rotigotine behenate extended-release microspheres.

Continuous dopaminergic stimulation (CDS) has become an important strategy for the development of drugs to treat Parkinson's disease (PD). Rotigotine behenate extended-release microspheres (RBEM) for injection represent a new treatment regime for CDS and are undergoing clinical trials. In this study, we aimed to investigate the effect of RBEM on genotoxicity, fertility and early embryonic development. We used the Ames test, Chinese hamster lung (CHL) cell chromosome aberration test and the mouse bone marrow micronucleus test, to evaluate the genotoxicity of RBEM. These tests were all negative, thus indicating that RBEM did not induce genotoxicity. In reproduction toxicity testing in male rats on obvious findings following intramuscular administration (i.m.) of RBEM at up to 540 mg/kg (P > 0.5), when female rats were administered with RBEM in the dose range of 60 to 540 mg/kg given (i.m.), there were clear effects on fertility and early embryonic development. These results indicated that RBEM could induce toxicity in female rats and exert effect on fertility and early embryonic development stage.

Characterization of enteric-coated erythromycin tablets by Raman mapping and its pharmaceutical evaluation.

Enteric tablet coating thickness is a critical quality attribute of the coating process that can affect dissolution behavior in vitro as well as release in vivo. Raman mapping offers unique advantages in analyzing the distribution of active pharmaceutical ingredients and excipients in formulations. In this study, Raman mapping was used to characterize the coating of enteric-coated erythromycin tablets coated by two different processes and compare the differences in their coating formulation, thickness, and uniformity. Furthermore, we aimed to select the appropriate pH of the dissolution medium at which the coating slowly cracks to release the drug and determine the dissolution profile. The differences in the coating thickness and uniformity of the two products resulted in differences in dissolution behavior. Although there are differences in the coating processes for the two types of enteric-coated erythromycin tablets, the thickness of the outer coating on the side is a critical quality attribute in both processes. The outer coating of product A is relatively thick, and the thickness of the outer coating on the side affects the dissolution amount. The outer coating of product B is relatively thin, resulting in a short cracking time and large variation and a significant difference in the initial dissolution amounts between tablets. Raman mapping can be used to analyze the differences in coating formulations and for process evaluation.

Quantitative Analysis of Three Synthetic Cannabinoids MDMB-4en-PINACA, ADB-BUTINACA, and ADB-4en-PINACA by Thermal-Assisted Carbon Fiber Ionization Mass Spectrometry.

Recently, synthetic cannabinoids (SCs) have emerged as new psychoactive substances (NPS) and have been frequently added to e-liquids, leading to their abuse. In order to detect SCs in e-liquids quickly and accurately, a thermal-assisted carbon fiber ionization mass spectrometry technique has been developed. The introduction of a heat source helps to reduce the matrix effects. The results indicate that the ratio of the slope of the matrix curve (e-liquids matrix) and the standard curve (methanol solution) for SCs analysis is close to 1, indicating a minimized matrix effect of this method. Furthermore, this method exhibits good quantitative ability when applied to real samples. It does not require sample pretreatment and is sensitive enough to directly quantify SCs in e-liquids. Our method is characterized by the ability to achieve rapid and direct quantitative analysis with minimized matrix effects. It provides a rapid and simple method for analyzing SCs in e-liquids.

Fabrication and application of molecularly imprinted polymer doped carbon dots coated silica stationary phase.

Facing the difficulties in chromatographic separation of polar compounds, this investigation devotes to developing novel stationary phase. Molecularly imprinted polymers (MIPs) have aroused wide attention, owing to their outstanding selectivity, high stability, and low cost. In this work, a novel stationary phase based on carbon dots (CDs), MIP layer, and silica beads was synthesized to exploit high selectivity of MIPs, excellent physicochemical property of CDs, and outstanding chromatographic performances of silica microspheres simultaneously. The MIP doped CDs coated silica (MIP-CDs/SiO2) stationary phase was systematically characterized by scanning electron microscopy (SEM), Brunauer-Emmett-Teller (BET) surface area measurement, and carbon elemental analysis. Furthermore, the chromatographic performance of the MIP-CDs/SiO2 column was thoroughly assessed by using a wide variety of compounds (including nucleosides, sulfonamides, benzoic acids, and some other antibiotics). Meanwhile, the separation efficiency of the MIP-CDs/SiO2 stationary phase was superior to other kinds of stationary phases (e.g. nonimprinted NIP-CDs/SiO2, MIP/SiO2, and C18-SiO2). The results demonstrated that MIP-CDs/SiO2 column exhibited best performance in terms of chromatographic separation. For all tested compounds, the resolution value was not less than 1.60, and the column efficiency of MIP-CDs/SiO2 for thymidine was 22,740 plates/m. The results further indicate that the MIP-CDs/SiO2 column can combine the good properties of MIP, CDs, with those of silica microbeads. Therefore, the developed MIP-CDs/SiO2 stationary phase can be applied in the separation science and chromatography-based techniques.

The photocatalytic reduction of U(VI) by Ag-doped SnS2 materials under visible light.

Efficient degradation of uranium(VI) (U(VI)) in wastewater is an urgent problem because of the chemical toxicity and radiotoxicity. In this study, the Agx-SnS2 photocatalysts were compounded by a simple hydrothermal method, effectively removing U(VI) under visible light in water. Compared with SnS2, the results indicated that Agx-SnS2 would decrease the crystallinity without destroying the crystal structure. Moreover, it has excellent photocatalytic performance on the degradation rate of U(VI). Ag0.5-SnS2 exhibited a prominent photocatalytic reduction efficiency of UO22+ of about 86.4% under optical light for 75 min. This was attributed to Ag-doped catalysts, which can narrow the band gap and enhance absorption in visible light. Meanwhile, the doping of Ag promoted the separation of photoinduced carriers, so that more photogenerated charges participated in the photocatalytic reaction. The stability and reusability were verified by the cycle test and the potential photocatalytic mechanism was analyzed based on the experiment.

Evaluation of herb-drug interactions between compound Danshen dripping pills and clopidogrel based on the pharmacokinetics and pharmacodynamics in rats.

Compound Danshen dripping pills (CDDP), a well-known traditional Chinese medicine, is widely used to prevent and treat cardiovascular diseases. CDDP is usually prescribed in combination with clopidogrel (CLP), but the herb-drug interactions are rarely reported. This study evaluated the effects of CDDP on the pharmacokinetics and pharmacodynamics of coadministered CLP, and ensured the safety and efficacy of their usage. The trial design included a single-dose administration and multidose test for 7 consecutive days. Wistar rats received CLP alone or CLP combined with CDDP. After the final dose, plasma samples were collected at various time points, and the active metabolite H4 of CLP was analyzed by ultrafast liquid chromatography coupled with triple quadrupole tandem mass spectrometry. The main pharmacokinetic parameters of Cmax (maximum [or peak] serum concentration), Tmax (peak plasma time), t1/2 (half-time), AUC0-∞ (area under the concentration-time curve from dosing (time 0) to infinite time), and AUC0-t (area under the concentration-time curve from dosing [time 0] to time t) were calculated using the non-compartment model. In addition, prothrombin time, activated partial thromboplastin time, bleeding time, and adenosine diphosphate-induced platelet aggregation were evaluated for anticoagulation and antiplatelet aggregation activity. In this study, we found that CDDP had no significant effect on the metabolism of CLP in rats. In pharmacodynamic studies, the combination group showed significant synergistic antiplatelet activity compared with the CLP or CDDP groups alone. Based on pharmacokinetic and pharmacodynamic results, CDDP and CLP have synergistic effects on antiplatelet aggregation and anticoagulation.

Studying spatial drug distribution in golf ball-shaped microspheres to understand drug release.

Poly (lactic-co-glycolic acid) (PLGA) microspheres have been one of the most successful products for slow drug release. While distribution of drugs in microspheres might be a fundamental factor affecting drug release, it has been often overlooked. Indeed, very few studies are available on the distribution of drugs in microspheres with complex morphology like golf ball-shaped microspheres. In this paper, the distribution of rotigotine in golf ball-shaped microspheres (GSRM) was investigated by argon ion milling, combined with scanning electron microscopy and energy dispersive X-ray spectroscopy (AIM-SEM-EDS). Rotigotine in GSRM was clearly observed in two forms, respectively in an aggregated state and as a molecular dispersion. The distribution of palmitic acid in the microspheres (used as an additive to reduce burst release) was also demonstrated: 10% was found on the microspheres' surface while 90% separated from the polymer to form small particles inside the microspheres onto which rotigotine aggregated through hydrogen bonding interactions. In in-vitro release studies we observed that first the phase-separated palmitic acid/rotigotine particles dissolved and released the drug, followed by the release of the molecularly dispersed rotigotines by osmosis. We also found that rotigotine accelerated the degradation and reduced the glass transition temperature of PLGA, which played an important role as well in the release of the drug from GSRM. Finally, two linear Level A in vitro-in vivo correlations were established and validated, indicating that the in vitro release testing could be a meaningful predictor for the in vivo performance of GSRM. Our work demonstrates the importance of studying drug distribution in complex microspheres to understand drug release.

Metabolic profiling of clonazolam in human liver microsomes and zebrafish models using liquid chromatography quadrupole Orbitrap mass spectrometry.

Clonazolam is a designer benzodiazepine with strong sedative and amnesic effects. As we all know, the detection of metabolites is the key to confirming the use of substances in the field of forensic toxicology. In order to better describe clonazolam metabolism completely, we performed the two different experiments exploiting the unique characteristics of the models used. In this study, in vivo and in vitro samples were analyzed with liquid chromatography-quadrupole/electrostatic field orbitrap mass spectrometry. The results showed that seven Phase I metabolites and one Phase II metabolite were detected in zebrafish model. The remaining Phase I and II metabolites were also found in the incubation solution of pooled human liver microsomes. The main types of metabolic reactions of clonazolam included hydroxylation, dealkylation, nitroreduction, dechlorination, N-Acetylation, and O-glucuronidation. In this paper, the main metabolites and metabolic pathways of clonazolam are clarified in detail in order to further improve the metabolic rule of clonazolam. Based on these results, to better detect and judge the abuse of clonazolam, we suggest that M1, its nitro reduction product, is used as its biomarker. The results of this study provide a theoretical basis for the pharmacokinetics and forensic medicine of clonazolam.

Optimization and validation of the liquid chromatography coupled to tandem mass spectrometry method for assessing octreotide release from microspheres during inflammation in rabbit models.

To study the effect of acute-phase reaction (APR) of inflammation on the release of octreotide acetate microsphere (Sandostatin®, SLAR) at a clinical dose, a more sensitive liquid chromatography coupled to tandem mass spectrometry analysis method needs to be developed because of the low plasma concentrations of octreotide. Solid-phase microextraction with an Oasis® HLB µElution plate was adopted for sample preparation. Extraction recovery ranged from 65.7 % to 73.2 %, and the matrix effect was negligible. High sensitivity and an intense chromatographic peak were acquired by optimizing the chromatography and mass spectrometry conditions. The lower limit of quantitation (LLOQ) was 0.01 ng/mL based on 100 µL of plasma, and linearity ranged from 0.01 to 5.0 ng/mL. The coefficients of variations for intraday and interday precision were less than 4.4 %, and the relative error of accuracy was within 5.7 %. The validated method was successfully applied to pharmacokinetics studies of SLAR in a seven-day inflammation model of rabbits, indicating that the APR did not affected the release and pharmacokinetics of the octreotide microspheres.

In Silico and In Vivo Pharmacokinetic Evaluation of 84-B10, a Novel Drug Candidate against Acute Kidney Injury and Chronic Kidney Disease.

Acute kidney injury (AKI) and chronic kidney disease (CKD) have become public health problems due to high morbidity and mortality. Currently, drugs recommended for patients with AKI or CKD are extremely limited, and candidates based on a new mechanism need to be explored. 84-B10 is a novel 3-phenylglutaric acid derivative that can activate the mitochondrial protease, Lon protease 1 (LONP1), and may protect against cisplatin-induced AKI and unilateral ureteral obstruction- or 5/6 nephrectomy [5/6Nx]-induced CKD model. Preclinical studies have shown that 84-B10 has a good therapeutic effect, low toxicity, and is a good prospect for further development. In the present study, the UHPLC-MS/MS method was first validated then applied to the pharmacokinetic study and tissue distribution of 84-B10 in rats. Physicochemical properties of 84-B10 were then acquired in silico. Based on these physicochemical and integral physiological parameters, a physiological based pharmacokinetic (PBPK) model was developed using the PK-Sim platform. The fitting accuracy was estimated with the obtained experimental data. Subsequently, the validated model was employed to predict the pharmacokinetic profiles in healthy and chronic kidney injury patients to evaluate potential clinical outcomes. Cmax in CKD patients was about 3250 ng/mL after a single dose of 84-B10 (0.41 mg/kg), and Cmax,ss was 1360 ng/mL after multiple doses. This study may serve in clinical dosage setting in the future.

Cobalt/calcium bimetallic oxides based on bio-waste eggshells for the efficient degradation of norfloxacin by peroxymonosulfate activation.

Cobalt-calcium bimetallic oxide (ECCO) was successfully prepared using eggshells and cobalt nitrate, which could be used to activate peroxymonosulfate (PMS) to remove norfloxacin (NOR). The compositional structure and surface properties of the catalysts were explored by various characterization analysis. The degradation efficiency of ECCO was 7.86 and 440 times higher than that of cobalt oxide and calcium oxide, respectively. The prepared ECCO (0.1 g/L) had a high degradation efficiency of over 90% against NOR (10 mg/L, 100 mL) by activating the PMS (0.15 g/L) at a wide pH range of 3.0-9.0 in 35 min. With a NOR removal efficiency of 91.4% after five cycles, the catalyst showed good reusability. The high degradation efficiency of NOR was resulted from enhanced electron transfer capability, the low point of zero charge and diversified reactive oxygen species (ROS). The ROS were identified as SO4•-, •OH and 1O2, which were produced by activating PMS on the active sites of Co and oxygen vacancies. It is the first report of the use of eggshells to synthesize cobalt-calcium bimetallic oxides ECCO for the activation of PMS to eliminate NOR, which is important for the development of green and efficient catalysts.

Trace Level Quantification of 4-Methyl-1-nitrosopiperazin in Rifampicin Capsules by LC-MS/MS.

Rifampicin is a first-line anti-tuberculosis drug. However, in August 2020, the presence of 1-methyl-4-nitrosopiperazine (MNP), a nitrosamine impurity, was detected by the United Stated Food and Drug Administration (US FDA) in rifampicin capsules. Consequently, the development of efficient methods for the detection of MNP is an important objective. In this study, the MNP present in rifampicin capsules was detected using LC-MS/MS. A total of 27 batches from nine manufacturers in the Chinese market were tested, with MNP (0.33-2.36 ppm) being detected in all samples at levels exceeding the maximum acceptable intake limit of 0.16 ppm initially set by the FDA. However, after considering the associated benefits and risks, the FDA-approved limit was revised to 5 ppm; hence, all the samples examined herein exhibited MNP levels well below the required limit. Furthermore, the results of forced degradation experiments suggest that MNP is formed by the thermal degradation of rifampicin.