Prescription ·Strong evidence ·Reviewed May 2026
Cefixime is an oral third-generation cephalosporin antibiotic used to treat a range of bacterial infections, including urinary tract infections, otitis media, pharyngitis, and uncomplicated gonorrhea. It is notable for being one of the few orally bioavailable third-generation cephalosporins and offers broad activity against many Gram-negative organisms. Its use in gonorrhea is now limited because of widespread reduced susceptibility of Neisseria gonorrhoeae.
The bottom line
Evidence rating strong. Most-documented uses: uncomplicated urinary tract infections, acute otitis media, pharyngitis and tonsillitis caused by streptococcus pyogenes. 3 sources indexed (1989–2021), with 5 interaction records on file.
Core mechanism
Cefixime is a beta-lactam antibiotic that inhibits bacterial cell wall synthesis by binding to and inactivating penicillin-binding proteins (PBPs), which are transpeptidase enzymes responsible for cross-linking peptidoglycan strands in the bacterial cell wall. Disruption of cross-linking weakens the cell wall and leads to autolysis and bacterial death. As a third-generation cephalosporin, cefixime is relatively stable against many beta-lactamases and has enhanced activity against Gram-negative bacteria compared with earlier generations, though it has limited activity against Pseudomonas aeruginosa, staphylococci, and enterococci.3,1
Cefixime can be taken with or without food; food does not clinically meaningfully impair absorption, though taking with food may modestly delay peak levels. Oral bioavailability is approximately 40-50 percent. The suspension formulation produces higher peak serum levels than tablets and is preferred when treating otitis media.
Nutrients this medication can lower over time, and what to replace.
Broad-spectrum cephalosporins suppress colonic bacteria (notably Bacteroides species) that synthesize menaquinones (vitamin K2), reducing the endogenous vitamin K pool available for hepatic clotting-factor carboxylation. Unlike cephalosporins bearing an N-methylthiotetrazole (NMTT) side chain, cefixime does not directly inhibit vitamin K epoxide reductase, so the effect is mediated chiefly through gut-flora disruption and is usually clinically meaningful only with prolonged courses, poor dietary intake, or concurrent warfarin therapy.
Cefixime can suppress or kill bacterial probiotic organisms if taken at the same time, although selected probiotics may lower antibiotic-associated diarrhea risk.
Recommendation: Separate probiotic doses from the antibiotic by at least 2 hours when feasible; avoid probiotic use in severely immunocompromised patients or patients with central lines unless clinician-directed.
Prolonged Cefixime therapy can contribute to reduced vitamin K status in susceptible patients by altering gut flora, with higher concern in poor intake, malabsorption, liver disease, or warfarin use.
Recommendation: Do not self-treat bleeding or INR changes. Monitor for bruising or bleeding and coordinate vitamin K or anticoagulant changes with the prescriber.
Oral iron salts can reduce the absorption of cefixime by forming poorly soluble chelates in the gastrointestinal tract, potentially lowering antibiotic plasma concentrations and reducing efficacy against the target infection.
Recommendation: Separate iron supplements from cefixime by at least 2 to 3 hours. Take cefixime first and the iron later, and complete the full antibiotic course as prescribed.
Calcium-containing supplements and antacids may bind cefixime in the gut, reducing its dissolution and absorption and potentially undermining treatment of the infection.
Recommendation: Take calcium supplements at least 2 hours apart from cefixime. Prioritize completing the antibiotic course on schedule.
Broad-spectrum antibiotics including cephalosporins can suppress vitamin K-producing gut flora during prolonged or repeated courses, which may modestly lower vitamin K status. Vitamin K2 supplementation is generally protective rather than harmful in this setting.
Recommendation: No routine action is needed for typical short cefixime courses. Patients on chronic anticoagulants or with poor nutritional intake should monitor for signs of bleeding and discuss vitamin K intake with their clinician.
Numbered references. Citations throughout the page link here.
Ceftriaxone is the preferred treatment for gonorrhea; cefixime 800 mg orally is an alternative only when ceftriaxone is not an option, due to declining gonococcal susceptibility to cefixime.
Cefixime demonstrated clinical and bacteriological efficacy comparable to other agents in urinary, respiratory, and ear-nose-throat infections, with a once- or twice-daily dosing advantage from its long half-life.
Cefixime is bactericidal through inhibition of cell wall synthesis, with activity against many Gram-negative organisms and oral bioavailability of about 40-50 percent.
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