Cefazolin, also known as cefazoline and cephazolin, is a first-generation cephalosporin antibiotic used for the treatment of a number of bacterial infections. Specifically it is used to treat cellulitis, urinary tract infections, pneumonia, endocarditis, joint infection, and biliary tract infections. It is also used to prevent group B streptococcal disease around the time of delivery and before surgery. It is typically given by injection into a muscle or vein. Common side effects include diarrhea, vomiting, yeast infections, and allergic reactions. Historically, it was thought to be contraindicated in patients with allergies to penicillin, although several recent studies have refuted this and it is proven to be safe in almost all patients, including those with known penicillin allergies. It is relatively safe for use during pregnancy and breastfeeding. Cefazolin is in the first-generation cephalosporin class of medication and works by interfering with the bacteria's cell wall. Cefazolin was patented in 1967 and came into commercial use in 1971. It is on the World Health Organization's List of Essential Medicines. It is available as a generic medication. Medical uses Cefazolin is used in a variety of infections provided that susceptible organisms are involved. It is indicated for use in the following infections: Respiratory tract infections Urinary tract infections Skin infections Biliary tract infections Bone and joint infections Genital infections Blood infections (sepsis) Endocarditis It can also be used peri-operatively to prevent infections post-surgery, and is often the preferred drug for surgical prophylaxis. There is no penetration into the central nervous system and therefore cefazolin is not effective in treating meningitis. Cefazolin has been shown to be effective in treating methicillin-susceptible Staphylococcus aureus (MSSA) but does not work in cases of methicillin-resistant Staphylococcus aureus (MRSA). In many instances of staphylococcal infections, such as bacteremia, cefazolin is an alternative to penicillin in patients who are allergic to penicillin. However, there is still potential for a reaction to occur with cefazolin and other cephalosporins in patients allergic to penicillin. Resistance to cefazolin is seen in several species of bacteria, such as Mycoplasma and Chlamydia, in which case different generations of cephalosporins may be more effective. Cefazolin does not fight against Enterococcus, anaerobic bacteria or atypical bacteria among others. Bacterial susceptibility As a first-generation cephalosporin antibiotic, cefazolin and other first-generation antibiotics are very active against gram-positive bacteria and some gram-negative bacteria. Their broad spectrum of activity can be attributed to their improved stability to many bacterial