Mezlocillin sodium is primarily used as an antibiotic in the treatment of various bacterial infections. It is effective against a wide range of Gram-negative and some Gram-positive bacteria, making it useful in combating infections such as urinary tract infections, respiratory tract infections, septicemia, and intra-abdominal infections. It is often administered intravenously or intramuscularly, particularly in hospital settings, to ensure rapid and effective delivery. Additionally, it is sometimes used in combination with other antibiotics to enhance its efficacy, especially in treating severe or complicated infections. Its broad-spectrum activity makes it a valuable option in managing infections caused by susceptible organisms, particularly when resistance to other antibiotics is a concern.