Melocillin is a penicillin, a semi-synthetic, broad-spectrum penicillin, and is a third-generation penicillin antibiotic. Melocillin, also known as sulfadiazole benzylpenicillin, is a derivative of ampicillin and is commonly available in injectable form for intravenous or intramuscular injection, mainly used for the treatment of infectious diseases caused by Pseudomonas aeruginosa and other susceptible Gram-negative bacilli, e.g., respiratory infections, urinary tract infections, and infections of the reproductive system. Melocillin can cause adverse reactions such as nausea, vomiting, lack of appetite, diarrhea, local pain and rash from intramuscular injection, and is contraindicated for those who are allergic to penicillins. Before using Melocillin, skin test should be done so as to determine whether you are allergic to this product and avoid causing serious allergic reactions after use. When using Meloxicillin, if the patient has an uncomfortable reaction, he should contact the doctor in time.