Bleeding Complications After Breast Core-needle Biopsy-An Approach to Managing Patients on Antithrombotic Therapy

Image-guided core-needle breast and axillary biopsy (CNB) is the standard-of-care procedure for the diagnosis of breast cancer. Although the risks of CNB are low, the most common complications include bleeding and hematoma formation. Post-procedural bleeding is of particular concern in patients taking antithrombotic therapy, but there is currently no widely established standard protocol in the United States to guide antithrombotic therapy management. In the face of an increasing number of patients taking antithrombotic therapy and with the advent of novel classes of anticoagulants, the American College of Radiology guidelines recommend that radiologists consider cessation of antithrombotic therapy prior to CNB on a case-by-case basis. Lack of consensus results in disparate approaches to patients on antithrombotic therapy undergoing CNB. There is further heterogeneity in recommendations for cessation of antithrombotic therapy based on the modality used for image-guided biopsy, target location, number of simultaneous biopsies, and type of antithrombotic agent. A review of the available data demonstrates the safety of continuing antithrombotic therapy during CNB while highlighting additional procedural and target lesion factors that may increase the risk of bleeding. Risk stratification of patients undergoing breast interventional procedures is proposed to guide both pre-procedural decision-making and post-procedural management. Radiologists should be aware of antithrombotic agent pharmacokinetics and strategies to minimize post-procedural bleeding to safely manage patients.

Management of Anticoagulant and Antiplatelet Medications in Adults Undergoing Percutaneous Interventions

OBJECTIVE

Many radiologists are unfamiliar with the new antithrombogenic medications and how to modify patient management before nonvascular percutaneous procedures performed in a radiology department. In this article, we review the indications for use, mechanism of action, pharmacokinetics, dosing, and recommendations for periprocedural management of patients using these medications.

CONCLUSION

To improve patient safety, radiologists involved in percutaneous procedures should have knowledge of the antithrombotics that will be encountered routinely in clinical practice.

5-alkyl-1,3-oxazole derivatives of 6-amino-nicotinic acids as alkyl ester bioisosteres are antagonists of the P2Y12 receptor

BACKGROUND

Recently, we reported ethyl nicotinates as antagonists of the P2Y12 receptor, which is an important target in antiplatelet therapies. A potential liability of these compounds was their generally high in vivo clearance due to ethyl ester hydrolysis.

RESULTS

Shape and electrostatic similarity matching was used to select five-membered heterocycles to replace the ethyl ester functionality. The 5-methyl and 5-ethyl-oxazole bioisosteres retained the sub-micromolar potency levels of the parent ethyl esters. Many oxazoles showed a higher CYP450 dependent microsomal metabolism than the corresponding ethyl esters. Structure activity relationship investigations supported by ab initio calculations suggested that a correctly positioned alkyl substituent and a strong hydrogen bond acceptor were necessary structural motifs for binding. In rat pharmacokinetics, the low clearance was retained upon replacement of an ethyl ester with a 5-ethyl-oxazole.

CONCLUSION

The use of shape and electrostatic similarity led to the successful replacement of a metabolically labile ethyl ester functionality with 5-alkyl-oxazole bioisosteres.

A novel series of piperazinyl-pyridine ureas as antagonists of the purinergic P2Y12 receptor

A novel series of P2Y(12) antagonists for development of drugs within the antiplatelet area is presented. The synthesis of the piperazinyl-pyridine urea derivatives and their structure-activity relationships (SAR) are described. Several compounds showed P2Y(12) antagonistic activities in the sub-micromolar range.

The dual nature of extracellular ATP as a concentration-dependent platelet P2X1 agonist and antagonist

Patient groups subject to higher occurrence of stroke (e.g., people with diabetes, cystic fibrosis, pulmonary hypertension) have reduced release of ATP from their erythrocytes (ERYs) when subjected to flow-induced deformation or pharmacological stimuli. These same groups also have platelets that are more adhesive in comparison to controls. Here we show platelet aggregation, and inhibition of that aggregation, is affected by free Ca(2+) entering the platelet through the ATP-gated P2X1 receptor. The addition of ATP (10 microM) increased the platelet NO by 26.7 +/- 7.7%. This value was decreased significantly to below basal levels in the presence of NF 449 (p < 0.001), an inhibitor of the P2X1 receptor on the platelet. Aggregation profiles measured in the presence of ATP revealed that when the P2X1 receptor was blocked, or when the measurements were performed in Ca(2+) free buffer, platelet aggregation was nearly eliminated. Our findings employing standard aggregation measurements suggest that ATP behaves as a platelet inhibitor below 1.6 x 10(-19) moles ATP per platelet; however, above this value, ATP behaves as a platelet activator. These findings suggesting a dual nature of ATP with regard to platelet behavior were confirmed by passing platelets over endothelial cells that were coated in the channels of a microfluidic device. Importantly, it was determined that ERY-derived ATP release was a major determinant of platelet adhesion to the endothelium. These findings may have implications in anti-platelet drug design as most current therapies focus on the inhibition of P2Y-type receptors. Moreover, through the use of microfluidic technologies, we have provided in vitro evidence for a possible relationship between ERY properties and platelet behavior in vivo.