Methicillin is an antibiotic that belongs to the penicillin class of drugs. It was developed in the 1950s to treat infections caused by Staphylococcus aureus bacteria, particularly those that are resistant to other penicillins. Methicillin works by inhibiting bacterial cell wall synthesis, effectively stopping the growth of bacteria. However, the use of methicillin has declined due to the emergence of methicillin-resistant Staphylococcus aureus (MRSA), a strain of bacteria that has developed resistance to this antibiotic. As a result, healthcare providers often use alternative antibiotics to treat infections caused by MRSA and other resistant bacteria.