methicillin

This term refers to a specific pharmaceutical agent within the penicillin class. In clinical settings, it is primarily discussed in the context of antibiotic resistance, specifically regarding the emergence of methicillin-resistant Staphylococcus aureus (MRSA). Because it is a chemical compound and a specific drug, it is treated as an uncountable mass noun.

Usage is almost exclusively restricted to medical, pharmacological, and biological registers. It is rarely used in general conversation unless discussing a specific medical diagnosis or a laboratory result.