Paracetamol increases INR during warfarin therapy and should be limited to no more than 2 g per week. Pharmacology
Pharmacodynamics
Paracetamol appears to exert its effects through two mechanisms: the inhibition of cyclooxygenase and actions of its metabolite AM404.Supporting the first mechanism, pharmacologically and in its side effects, paracetamol is close to classical nonsteroidal anti-inflammatory drugs (NSAIDs) that act by inhibiting COX-1 and COX-2 enzymes and especially similar to  selective COX-2 inhibitors. Paracetamol inhibits prostaglandin synthesis by reducing the active form of COX-1 and COX-2 enzymes. This occurs only when the concentration of arachidonic acid and peroxides is low. Under these conditions, COX-2 is the predominant form of cyclooxygenase, which explains the apparent COX-2 selectivity of paracetamol. Under the conditions of inflammation, the concentration of peroxides is high, which counteracts the reducing effect of paracetamol. Accordingly, the anti-inflammatory action of paracetamol is slight. The anti-inflammatory action of paracetamol (via COX inhibition) has also been found to primarily target the central nervous system and not peripheral areas of the body, explaining the lack of side effects associated with conventional NSAIDs such as gastric bleeding. The second mechanism centers on the paracetamol metabolite AM404. This metabolite has been detected in the brains of animals and cerebrospinal fluid of humans taking paracetamol. Apparently, it is formed in the brain from another paracetamol metabolite 4-aminophenol by action of fatty acid amide hydrolase. AM404 is a weak agonist of cannabinoid receptors CB1 and CB2, an inhibitor of endocannabinoid transporter, and a potent activator of TRPV1 receptor.
An empyema () is a collection or gathering of pus within a naturally existing anatomical cavity. For example, pleural empyema is empyema of the pleural cavity. It must be differentiated from an abscess, which is a collection of pus in a newly formed cavity. The term is from Greek ἐμπύημα, "abscess". Classification
Empyema occurs in:

the pleural cavity (pleural empyema also known as pyothorax)
the thoracic cavity
the uterus (pyometra)
the appendix (appendicitis)
the meninges (subdural empyema)
the joints (septic arthritis)
the gallbladder

External links

Shen, K. Robert; Bribriesco, Alejandro; Crabtree, Traves; Denlinger, Chad; Eby, Joshua; Eiken, Patrick; Jones, David R.; Keshavjee, Shaf; Maldonado, Fabien; Paul, Subroto; Kozower, Benjamin (February 2017). "The American Association for Thoracic Surgery consensus guidelines for the management of empyema". The Journal of Thoracic and Cardiovascular Surgery. 153 (6): e129–e146. doi:10.1016/j.jtcvs.2017.01.030. PMID 28274565.