# Penicillin

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Penicillin refers to a class of antibiotic drugs that have a common ${\displaystyle \beta }$-lactam core structure. Characteristics of penicillins, especially bioavailability, can vary substantially depending upon the R- group appended onto the core structure. Some penicillin drugs are actually prodrugs that only become active after some metabolitic transformation within a patient. Penicillin drug may cause severe, even fatal, allergic responses in some patients. Some bacteria have developed resistance to penicillin through the acquisition of ${\displaystyle \beta }$-lactamases, enzymes which degrade the ${\displaystyle \beta }$-lactam structures of the penicillin drugs.