Cefoxitin

How Medicare covers it

Part B (injection/infusion given by a clinician — see the Part B basis in this package; the usual path for this drug). The Part D aggregation in this package is carried exactly as computed — the formulary file carries the injection concepts. Part A during a covered inpatient stay.

What it treats

Cefoxitin for Injection (brand name Mefoxin) treats serious infections caused by bacteria it can kill: lower respiratory tract infections including pneumonia and lung abscess; urinary tract infections; intra-abdominal (belly) infections including peritonitis and abscess; gynecological infections including endometritis, pelvic cellulitis, and pelvic inflammatory disease; septicemia (blood infection); bone and joint infections; and skin and skin structure infections. It is also used to prevent infection in patients having uncontaminated gastrointestinal surgery, vaginal hysterectomy, abdominal hysterectomy, or cesarean section. It has no activity against Chlamydia trachomatis.

What it is for, in depth

Cefoxitin is an intravenous hospital antibiotic, sold under the brand name Mefoxin, with unusually wide coverage that includes anaerobic bacteria such as Bacteroides fragilis, which many cephalosporins miss. Doctors use it for serious infections of the lungs, urinary tract, abdomen, female reproductive organs, blood, bones and joints, and skin, when the infection is caused by bacteria on its label list — including staphylococci, streptococci, E. coli, Klebsiella, and Proteus. It is also given around the time of surgery — gastrointestinal surgery, hysterectomy, and cesarean section — to prevent surgical infections. It is given only by vein, usually 1 to 2 grams every 6 to 8 hours, with the dose reduced when the kidneys do not work well. Cefoxitin comes only as a powder for injection in 1 gram and 2 gram vials; there is no pill form.

How it works

Cefoxitin is a cephalosporin (cephamycin) antibiotic. It kills bacteria (it is bactericidal) by blocking the building of the bacterial cell wall. It stays active in the presence of some beta-lactamases — enzymes bacteria make to destroy penicillin-type and cephalosporin antibiotics — which is why it can work against some bacteria that resist other drugs in those classes, including many anaerobic bacteria such as Bacteroides species.

How it is taken

Cefoxitin is given into a vein (intravenously) in a hospital or infusion setting. The usual adult dose is 1 gram to 2 grams every 6 to 8 hours: 1 gram every 6 to 8 hours (3 to 4 grams a day) for uncomplicated infections such as pneumonia, urinary tract infection, or skin infection; 6 to 8 grams a day for moderately severe or severe infections; and up to 12 grams a day for infections that need higher doses, such as gas gangrene. For prevention at surgery, 2 grams is given about one-half to one hour before the operation and then every 6 hours for no more than 24 hours. The dose is lowered in patients with reduced kidney function. For children 3 months of age and older, the dose is 80 to 160 mg/kg of body weight per day divided into four to six equal doses. It comes as a powder in vials of 1 gram and 2 grams that is mixed with liquid before use.

Common side effects

Cefoxitin is generally well tolerated, and the most common side effects have been local reactions after intravenous injection, including thrombophlebitis (inflammation of the vein). Other effects reported include rash, hives (urticaria), flushing, itching, fever, diarrhea, nausea and vomiting (reported rarely), low blood pressure (hypotension), and changes in blood and liver tests such as eosinophilia (raised eosinophils), low white blood cells, anemia, raised liver enzymes (SGOT, SGPT, LDH, and alkaline phosphatase), and raised creatinine or blood urea nitrogen.

Serious warnings

Serious allergic (hypersensitivity) reactions, including anaphylaxis, angioedema, interstitial nephritis, and severe skin reactions such as exfoliative dermatitis and toxic epidermal necrolysis, have been reported; if an allergic reaction occurs, the drug must be stopped and emergency treatment may be needed. Diarrhea caused by Clostridium difficile (CDAD) — which can range from mild diarrhea to fatal colitis (inflammation of the colon) — has been reported with nearly all antibacterial drugs including cefoxitin, and it can appear during treatment or more than two months after the last dose; pseudomembranous colitis has been reported. Rarely, acute renal (kidney) failure and blood problems such as bone marrow depression and hemolytic anemia have been reported. As with other antibiotics, prolonged use can lead to overgrowth of bacteria or fungi that cefoxitin cannot kill (superinfection).

Who should be careful

Cefoxitin must not be used by patients who have shown hypersensitivity (allergy) to cefoxitin or to the cephalosporin group of antibiotics. Before treatment, patients should be asked carefully about previous allergic reactions to cefoxitin, cephalosporins, penicillins, or other drugs, and the drug should be given with caution to penicillin-sensitive patients and to any patient with a history of allergy, and with caution in patients with a history of gastrointestinal disease, particularly colitis. The total daily dose should be reduced in patients with reduced urine output from kidney insufficiency, and kidney function should be watched in older patients. Safety and efficacy in infants from birth to 3 months of age have not been established. MedlinePlus notes that cefoxitin injection may decrease the effectiveness of hormonal contraceptives, so another method of contraception should be used while receiving it.

Major interactions

Increased kidney toxicity (nephrotoxicity) has been reported when cephalosporins are given together with aminoglycoside antibiotics such as gentamicin. Cefoxitin solutions should not be mixed in the same solution with aminoglycosides because of a potential interaction, although the two drugs may be given separately to the same patient. Probenecid slows the kidneys' excretion of cefoxitin and produces higher and longer-lasting blood levels. High concentrations of cefoxitin can also interfere with certain laboratory tests, including creatinine measurement, urinary 17-hydroxy-corticosteroid measurement, and urine glucose testing with Clinitest tablets, which may show a false-positive result.

Cost and saving notes

If this drug is covered under your Medicare Part D plan and the cost is high, you can ask your plan for a tier exception to pay a lower cost share. If you have limited income, Extra Help (the Part D Low-Income Subsidy) can lower your Part D premiums and drug costs. In 2027, your total yearly out-of-pocket spending on covered Part D drugs is capped at $2,400, and you can spread those costs out in monthly payments through the Medicare Prescription Payment Plan.

Why it is in its tier

Cefoxitin sits on Tier 4 in 77.62% of the plans that list it (4265 of 5495 listing plans). Tier 4 is the non-preferred tier — higher copays or coinsurance. The data-visible drivers: It is a generic product, and the CMS dashboard puts its average Part D spending at about $1,100 per beneficiary for 2024 — a mid-cost drug, which matches where plans place it. It is listed by 100.0% of Part D plans. The tier shown is the most common one; individual plans vary.

Sources

• CEFOXITIN INJECTION, POWDER, FOR SOLUTION [WG CRITICAL CARE, LLC] — DailyMed
• MedlinePlus — National Library of Medicine
• MedlinePlus — Cefoxitin Injection: MedlinePlus Drug Information

What official patient guides say

Cefoxitin is not a pill you take on your own. It is an antibiotic given into a vein, usually in a hospital or clinic, every six or eight hours. Each dose is a powder mixed with liquid, or a premixed product, given intravenously, and how many days you get it depends on your infection and how your body responds. You should begin to feel better in the first few days, but keep every appointment and use it until you finish the prescription, even if you feel better. Stopping too soon or skipping doses can leave the infection not fully treated and make the bacteria harder to kill. If a dose is missed, use it as soon as you remember, unless it is almost time for the next dose — then skip it, keep your regular schedule, and do not use a double dose. Your healthcare provider will tell you how the medication is stored, so store it only as directed. Keep all appointments with your doctor and the laboratory so your response can be checked, and tell your team about all medicines you take and any drug allergies. The patient page also notes that cefoxitin may make hormonal birth control work less well, so ask about another way to prevent pregnancy while receiving it.

Source: MedlinePlus — Cefoxitin Injection: MedlinePlus Drug Information

Part D formulary coverage

Source: CMS Prescription Drug Plan Formulary, Pharmacy Network, and Pricing Information Files — Monthly file 2026-10-15 (plan year 2027), file 2027_20261008.zip (data.cms.gov dataset ed1496ea-23e7-41f1-9292-172fa842ccfb): basic drugs formulary file + plan information file, both dated 20261031 inside the zip; downloaded and aggregated 2026-10-30. Medication RxCUI sets resolved through the NLM RxNav (RxNorm) API.

What you pay

A tier is not a price; what you pay depends on your plan, pharmacy, and benefit stage; Extra Help or Medicaid can lower it further.

Sources: CMS Plan Benefit Package + formulary data; CMS NADAC · Checked 2026-11-07

Similar medications

Other medications in the same FDA pharmacologic class (Cephalosporin Antibacterial):

• Cefaclor
• Cefadroxil (Duricef and others)
• Cefazolin sodium injection
• Cefdinir (Omnicef and others)
• Cefepime injection (Maxipime and others)
• Cefixime (Suprax and others)
• Cefotetan
• Cefpodoxime (Vantin and others)
• Ceftaroline fosamil (Teflaro)
• Ceftazidime (Tazicef, Fortaz)
• Ceftazidime / avibactam (Avycaz)
• Ceftobiprole Medocaril (Zevtera)

Read next

• Part D in 2027: The $700 Deductible, the $2,400 Cap, and the $35 Insulin Rule
• Extra Help in 2027: Lower Drug Copays and Who Qualifies
• Checking Medicare Savings Programs and Extra Help

Part D spending averages (2024)

Source: CMS Medicare Part D Spending by Drug (Drug Spending Dashboard), release RY26 P04 V10, data through 2024 (DSD_PTD_RY26_P04_V10_DY24_BGM.csv), downloaded 2026-10-30

Companies covering this drug

5,495 plans from 509 companies list this drug on a formulary for 2027. Search by company or plan name, or filter by tier. Cost sharing is the plan's published amount for this drug's tier in the initial coverage stage (1-month retail supply), where the plan publishes it; a blank means the plan does not publish it.

A tier is not a price; what you pay depends on your plan, pharmacy, and benefit stage; Extra Help or Medicaid can lower it further.