Stability in clinical use and stress testing of meropenem antibiotic by direct infusion ESI-Q-TOF: Quantitative method and identification of degradation products.

An ESI-MS/MS method through direct infusion was validated for quantitative analysis of meropenem powder for injection. The validation parameters were established in a rapid analysis of 30 s. Drug stability was studied through the submission to stress testing, resulting on four degradation products. Under hydrolytic conditions, in acid, neutral and alkaline media, the major degradation product was formed through the cleavage of the ß-lactam ring. Oxidation of the drug using H2O2 (3%) showed the formation of two degradation products from a decarboxylation reaction and N-oxide formation. Under high humidity conditions, there was detected a dimer product. The stability of meropenem after reconstitution was studied in conditions that simulate its clinical use. In samples reconstituted and diluted in infusion fluids, an extensive degradation was observed. At room temperature meropenem maintained its content > 90% for up to 4 h when prepared in 5% glucose and for up to 12 h when prepared in 0.9% NaCl. Through ESI-MS/MS analyzes it was observed a degradation product formed by ß-lactam ring cleavage, detected in all conditions studied. It was also identified a degradation product formed only in 5% glucose, generated by the hydrolysis of ß-lactam followed by the attachment of a glucose molecule to the nitrogen of the pyrrolidine ring. In general, all the results obtained in the stability studies contribute to the knowledge about this antibiotic and future candidates of this class.

Stability and degradation products of imipenem applying high-resolution mass spectrometry: An analytical study focused on solutions for infusion.

Carbapenems show recognized instability in aqueous solutions; therefore some care must be taken in their handling and preparation and their use in the hospital environment. The stability and degradation products of imipenem were investigated from conditions that simulate its clinical use. For this, a simple stability-indicating method by HPLC-DAD was validated with a focus on the quantitation of drug concentration remaining from infusion solutions (sodium chloride 0.9% and glucose 5%). The degradation products formed were identified by high-resolution mass spectrometry (ESI-Q-TOF-MS/MS), with detection of the [M + H]+ ions at m/z 318 (DP-1), m/z 599 (DP-2) and m/z 658 (DP-3). The most probable elemental compositions were obtained with a high degree of confidence, where the error between the masses observed and calculated was 1.25 ppm for DP-1, -0.33 ppm for DP-2 and 1.82 ppm for DP-3. The DP-1 degradation product resulted from cleavage of the ß-lactam ring; DP-2 corresponded to the drug dimer; and DP-3 was generated from the interaction between imipenem and cilastatin. The proposed method provides a safe and reliable alternative for the quantitation of imipenem, and the stability data obtained by ESI-Q-TOF help in understanding the drug behavior under the conditions of clinical use.

Extracellular ATP is Differentially Metabolized on Papillary Thyroid Carcinoma Cells Surface in Comparison to Normal Cells.

The incidence of differentiated thyroid cancer has been increasing. Nevertheless, its molecular mechanisms are not well understood. In recent years, extracellular nucleotides and nucleosides have emerged as important modulators of tumor microenvironment. Extracellular ATP is mainly hydrolyzed by NTPDase1/CD39 and NTPDase2/CD39L1, generating AMP, which is hydrolyzed by ecto-5'-nucleotidase (CD73) to adenosine, a possible promoter of tumor growth and metastasis. There are no studies evaluating the expression and functionality of these ectonucleotidases on normal or tumor-derived thyroid cells. Thus, we investigated the ability of thyroid cancer cells to hydrolyze extracellular ATP generating adenosine, and the expression of ecto-enzymes, as compared to normal cells. We found that normal thyroid derived cells presented a higher ability to hydrolyze ATP and higher mRNA levels for ENTDP1-2, when compared to papillary thyroid carcinoma (PTC) derived cells, which had a higher ability to hydrolyze AMP and expressed CD73 mRNA and protein at higher levels. In addition, adenosine induced an increase in proliferation and migration in PTC derived cells, whose effect was blocked by APCP, a non-hydrolysable ADP analogue, which is an inhibitor of CD73. Taken together, these results showed that thyroid follicular cells have a functional purinergic signaling. The higher expression of CD73 in PTC derived cells might favor the accumulation of extracellular adenosine in the tumor microenvironment, which could promote tumor progression. Therefore, as already shown for other tumors, the purinergic signaling should be considered a potential target for thyroid cancer management and treatment.