Performance Characteristics of Mass Spectrometry-Based Analytical Procedures for Quantitation of Nitrosamines in Pharmaceuticals: Insights from an Inter-laboratory Study.

With the discovery of carcinogenic nitrosamine impurities in pharmaceuticals in 2018 and subsequent regulatory requirements for risk assessment for nitrosamine formation during pharmaceutical manufacturing processes, storage or from contaminated supply chains, effective testing of nitrosamines has become essential to ensure the quality of drug substances and products. Mass spectrometry has been widely applied to detect and quantify trace amounts of nitrosamines in pharmaceuticals. As part of an effort by regulatory authorities to assess the measurement variation in the determination of nitrosamines, an inter-laboratory study was performed by the laboratories from six regulatory agencies with each of the participants using their own analytical procedures to determine the amounts of nitrosamines in a set of identical samples. The results demonstrated that accurate and precise quantitation of trace level nitrosamines can be achieved across multiple analytical procedures and provided insight into the performance characteristics of mass spectrometry-based analytical procedures in terms of accuracy, repeatability and reproducibility.

International Regulatory Collaboration on the Analysis of Nitrosamines in Metformin-Containing Medicines.

Recalls of some batches of metformin have occurred due to the detection of N-nitrosodimethylamine (NDMA) in amounts above the acceptable intake (AI) of 96 ng per day. Prior to the recalls, an international regulatory laboratory network had been monitoring drugs for nitrosamine impurities with each laboratory independently developing and validating multiple analytical procedures to detect and measure nitrosamines in metformin drugs used in their jurisdictions. Here, we provide an overview of the analysis of metformin active pharmaceutical ingredients (APIs) and drug products with 1090 samples (875 finished dosage forms (FDFs) and 215 API samples) tested beginning in November of 2019 through July of 2020. Samples were obtained internationally by a variety of approaches, including purchased, received from firms via information requests or selected by regional regulatory authorities (either at wholesalers or during GMP inspections). Only one nitrosamine (NDMA) was detected and was only present in some batches of metformin products. For API samples, 213 out of 215 lots tested had no measurable level of NDMA. For FDF samples tested, the number of batches with NDMA above the AI amount for patient safety was 17.8% (156/875). Based on these data, although the presence of NDMA was of concern, 82.2% of the samples of metformin drug products tested met quality and safety standards for patients. Regulatory agencies continue to collaborate extensively and work with marketing authorization holders to understand root causes of nitrosamine formation and agree on corrective actions to mitigate the presence of NDMA in future metformin batches.

Determination and quantitation of sildenafil and its major metabolite in the breast milk of a lactating woman.

A heavily pregnant woman was treated with Revatio(®) (Sildenafil) against idiopathic pulmonary arterial hypertension, prior to and after her accouchement. To investigate the transfer of sildenafil into breast milk and its metabolism shortly before breastfeeding to the neonatal, a new analytical method was developed and validated, using liquid chromatography tandem mass spectrometry. Additionally, while using linear ion trap scan mode experiments, further metabolites could be identified. Sample preparation was carried out, using solid-phase extraction. For quantification of sildenafil and its major metabolite N-desmethylsildenafil, sildenafil-d8 was used as an internal standard. Within a time frame of 17h covering two Revatio(®) intakes and three breast milk samplings, a concentration range from 1.64 to 4.49ng/ml (sildenafil) and from 1.18 to 1.82ng/ml (N-desmethylsildenafil) could be observed. The current method proved to be accurate and precise in a very low concentration range and establishes the first reported determination of sildenafil and N-desmethylsildenafil in human breast milk.

Potential metal impurities in active pharmaceutical substances and finished medicinal products - A market surveillance study.

A market surveillance study has been established by using different atomic spectrometric methods for the determination of selected elemental impurities of particular interest, to gain an overview about the quality of presently marketed drug products and their bulk drug substances. The limit tests were carried out with respect to the existing EMA guideline on the specification limits for residuals of metal catalysts or metal reagents. Also attention was given to the future implementation of two new chapters of the United States Pharmacopoeia (USP) stating limit concentrations of elemental impurities. The methods used for determination of metal residues were inductively coupled plasma-mass spectrometry (ICP-MS), inductively coupled plasma-optical emission spectrometry (ICP-OES), and atomic absorption spectrometry technologies (GFAAS, CVAAS, HGAAS). This article presents the development and validation of the methods used for the determination of 21 selected metals in 113 samples from drug products and their active pharmaceutical ingredients.

Pyrazolopyrimidines in 'all-natural' products for erectile dysfunction treatment: the unreliable quality of dietary supplements.

A herbal food supplement advertised as a potency pill was screened for the presence of PDE5 inhibitors. The resulting signals were characterised by UV, LC-MS in ESI-negative mode, and NMR spectroscopy using 1D and 2D experiments. Several substances were identified, bearing the basic chemical structure of sildenafil, but were not supposed to exhibit PDE5 inhibition. These compounds may be process-related impurities or by-products of different reaction steps in the synthesis of PDE5 analogues. As they were found to be present in different capsules at different concentrations, this is an example of the unreliable quality of dietary supplements.

Identification of new synthetic PDE-5 inhibitors analogues found as minor components in a dietary supplement.

A dietary supplement sold in erotic shops was analysed. It contains dithiodesmethylcarbodenafil as the major component, which was already reported as an adulterant in dietary supplements. Additionally three more compounds were found and their structures were elucidated after isolation using NMR and mass spectroscopy. They were designated as isonitrosoprodenafil, dithiodesethylcarbodenafil and norcarbodenafil.

Simultaneous determination of alkyl mesilates and alkyl besilates in finished drug products by direct injection GC/MS.

We report a specific, fast and feasible method for the simultaneous determination of methyl mesilate (MMS), ethyl mesilate (EMS), isopropyl mesilate (IMS), methyl besilate (MBS) and ethyl besilate (EBS) in finished drug products by GC/MS. Sample preparation was carried out by liquid extraction. The analytes were directly injected into the chromatographic system and quantified with the internal standard method using methyl tosylate (MTS) as internal standard (ISTD). The method gives excellent sensitivity for all the alkyl and aryl esters at typical target analyte level, according to the acceptance criteria that are described in the Guideline on the Limits of Genotoxic Impurities which has been issued in 2007 by the European Medicines Agency (EMA). The average recovery for methanesulfonic acid esters (mesilates) was not lower than 71%, for benzenesulfonic acid esters (besilates) not lower than 94%. A linear range with R² ≥ 0.9998 has been established for concentrations between 0.01 and 1.33 µg/ml. Validation of the method was carried out on a sample matrix containing MMS, EMS, IMS, MBS and EBS at relevant levels and was further confirmed on finished products containing APIs as mesilate salts (Bromocriptine mesilate, Doxazosin mesilate).

Identification of novel sildenafil-analogues in an adulterated herbal food supplement.

A new herbal product advertised as potency pill was sent for analysis by the local authority. The product was tested for the presence of potential derivatives of PDE-5 inhibitors, such as sildenafil, vardenafil, and tadalafil. Sildenafil analogues were identified, in which the piperazine ring and the sulfonyl group were replaced by a piperazinone and a hydroxyethyl structure, respectively. The chemical structures were established by LC-MS in ESI negative mode, UV and NMR spectroscopy (including DEPT, HSQC, HMBC, H,H-COSY, H,H-TOCSY and H,H-NOESY experiments). This is the first report of piperazinonafil and isopiperazinonafil as adulterant in an herbal food supplement.

The gramine route to pyrido[4,3-b]indol-3-ones - identification of a new cytotoxic lead.

A novel approach to 3-oxo-γ-carbolines was worked out starting from methyl indol-2-ylacetate via a gramine derivative. After quaternization, ammonia and 4-methoxybenzylamine could be inserted giving appropriate 3-oxo-γ-carbolines. Condensation with 2-chlorobenzaldehyde under microwave irradiation gave a 4-(2-chlorobenzyl)-3-oxo-γ-carboline. N-methylation lead to a product with very promising antifungal and cytotoxic activities.