Cefoxitin
Drug Name
Cefoxitin is a semi-synthetic bactericidal antibiotic and a derivative of cephamycin C, which is produced by Streptomyces lactamdurans. This cephamycin antibiotic is part of the β-lactam class and is a second-generation cephalosporin. It has broad-spectrum activity against a wide range of gram-negative bacteria, including anaerobic bacterial species (DrugBank).
Table 1. Basic profile of cefoxitin.
| Description | Intravenously administered, semi-synthetic broad-spectrum antibacterial drug |
| Target(s) | Penicillin-binding proteins (PBPs) |
| Generic | Cefoxitin (for injection) |
| Commercial Name | Mefoxin® (United States, Canada) |
| Combination Drug(s) | N/A |
| Other Synonyms | Cefoxitina, Cefoxitine, Cefoxitinum, Ceftoxitin, Cephoxitin, CFX, Rephoxitin, Mefoxitin |
| IUPAC Name | (6R,7S)-3-[(carbamoyloxy)methyl]-7-methoxy-8-oxo-7-[2-(thiophen-2-yl)acetamido]-5-thia-1-azabicyclo[4.2.0]oct-2-ene-2-carboxylic acid |
| Ligand Code in PDB | CFX; 1QL (bound form) |
| PDB structure | 3mze (3D Structure of cefoxitin bound to target protein PBP5) |
| ATC code | J01DC01 |
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Antibiotic Chemistry
Cefoxitin is a cephamycin antibiotic often grouped with second-generation cephalosporins. It is composed of a β-lactam ring (shown in pink in Figure 2) fused to a six-membered dihydrothiazine ring (shown in orange in Figure 2), which are characteristics of all cephalosporin antibiotics. Cefoxitin has a few additional structural features that contribute to its antibacterial properties. For instance, the 7α methoxy group (shown in purple in Figure 2) makes cefoxitin a poor substrate for β-lactamases (CARD, 2017), conferring less susceptibility to resistance against this drug.
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| Figure 2. 2D structure of cefoxitin highlighting functional moieties responsible for antibacterial activity. Structure was created using ChemDraw. |
Drug Information
Table 2. Chemical and physical properties (DrugBank).
| Chemical Formula | C16H17N3O7S2 |
| Molecular Weight | 427.5 g/mol |
| Calculated Predicted Partition Coefficient: cLogP | 0.22 |
| Calculated Predicted Aqueous Solubility: cLogS | -3.3 |
| Solubility (in water) | 0.195 mg/mL |
| Predicted Topological Polar Surface Area (TPSA) | 148.3 Å2 |
Drug Target
Cefoxitin disrupts cell wall biosynthesis by inhibiting enzymes known as penicillin-binding proteins (PBPs). The name originates from the ability of penicillin and other β-lactam antibiotics to bind to these proteins. Some of these PBP enzymes are responsible for catalyzing the final steps of the peptidoglycan synthesis pathway, which include polymerizing glycan strands and cross-linking adjacent chains to form the characteristic mesh structure of peptidoglycan. On the other hand, other PBPs are involved in regulating peptidoglycan recycling and cell wall remodeling. Peptidoglycan, which is a polymer consisting of amino acids (peptido-) and sugars (-glycan), is the major component of the bacterial cell wall, and its mesh-like structure provides the cell wall with structure and rigidity.
Learn more about PBPs.
Although cefoxtin has high affinities to nearly all the PBPs of Escherichia coli (Matsuhashi and Tamaki, 1978), the discussion here will be focused on how the antibiotic binds to and inhibits PBP5. Inhibition of the PBPs responsible for cross-linking results in a severely weakened cell wall, which then causes bacterial cell lysis and death. However, inhibition of those PBPs involved only in peptidoglycan remodeling, such as PBP5, is non-lethal to the bacteria.
Drug-Target Complex
The target of cefoxitin, PBP5, is made of two domains oriented at right angles to each other (Davies et al., 2000, Figure 3):
* Penicillin-binding domain (residues 3-262)
* C-terminal domain (residues 263-356)
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| Figure 3. Ribbon representation of the postcovalent two-domain structure of PBP5 bound to cefoxitin (color-coded atomic stick figure: C-spring green, N-blue, O-red, S-yellow). The inset shows the covalent linkage that forms between cefoxitin and Ser44 (color-coded atomic stick figure: C-gold, O-red) (PDB ID: 3mze; Nicola et al., 2010). |
PBP5 is involved in peptidoglycan remodeling and recycling and is the major carboxypeptidase in E. coli cells (Sauvage et al., 2008). The carboxypeptidase cleaves the terminal D-Ala of the peptide substrate and releases the shortened peptide (Sauvage et al., 2008). The active site is located in the penicillin-binding domain of the protein. The Ser44 nucleophile is where the D-Ala-D-Ala peptide bond of the glycan substrate binds and takes part in the carboxypeptidation reaction.
Learn more about PBP5.
The β-lactam ring of cefoxitin is a structural mimic of the backbone of the D-Ala-D-Ala peptide bond, which allows the antibiotic to occupy the same binding site as the natural substrate. Specifically, the antibiotic reacts with the Ser44 nucleophile and forms an acyl-enzyme covalent complex (Nicola et al., 2010, Figure 3). Cefoxitin is able to inhibit PBP5 by blocking the natural peptide substrate from accessing the active site of the enzyme. Consequently, the β-lactam blocks deacylation, which thus prevents carboxypeptidation and peptidoglycan remodeling.
The active site consists of a few important amino acid side chains that surround the bound antibiotic, as shown in Figure 4. Phe245 contributes to the hydrophobicity of the binding pocket, and Asn112 interacts with the 7α methoxy of cefoxitin through a hydrogen bond (Nicola et al., 2010). In addition, both nitrogen atoms of the Arg248 side chain participate in a bidentate interaction as they form hydrogen bonds with the carboxylate of the antibiotic (Nicola et al., 2010).
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| Figure 4. A close-up of the interactions cefoxitin participates in after binding to the active site of PBP5. Asn112, Phe245, and Arg248 (color-coded atomic stick figure: C-tan, N-blue, O-red) are a few of the residues that make up the binding pocket of the enzyme. Hydrogen bonding interactions are depicted in blue (PDB ID: 3mze; Nicola et al., 2010). |
A significant conformational change brings Phe245 and Arg248 closer to the active site where they can interact with the bound antibiotic (Nicola et al., 2010). As shown in Figure 5b, a loop region, consisting of residues 242-250, experiences a large shift when cefoxitin is bound to the enzyme so that Phe245 and Arg248 can be positioned near the binding pocket (Nicola et al., 2010). This shift appears to be driven by the strong electrostatic linkage between Arg248 and the carboxylate of the antibiotic (Nicola et al., 2010). Interestingly, when Arg248 is mutated, the normal carboxypeptidase activity of PBP5 is significantly reduced, which suggests that this residue may serve an important function in positioning the carboxylate of the terminal D-Ala of the peptide substrate during acylation (Nicola et al., 2010).
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| Figure 5. Comparison of the apo-structure and cefoxitin-bound structure of PBP5. (a) Ribbon representation of wild-type PBP5, showing Phe245 and Arg248 far from the active site (PDB ID: 1nzo; Nicholas et al., 2003). (b) Ribbon representation of the cefoxitin-bound PBP5 structure, showing Phe245 and Arg248 positioned closer to the binding pocket (PDB ID: 3mze; Nicola et al., 2010). The loop structure that shifts, resulting in the conformational change, is depicted in aquamarine. |
Pharmacologic Properties and Safety
Warnings: Cefoxitin should be given with caution to patients who have had previous hypersensitivity or allergic reactions to cephalosporins and penicillins (FDA, 2017).
Table 3. Pharmacokinetics: ADMET of cefoxitin. ***IC50 values were found and reported for 5 PBP enzymes found in Streptococcus pneumoniae. An IC50 value for PBP5 in E. coli was not found.
| Features | Comment(s) | Source |
|---|---|---|
| Oral Bioavailability (%) | N/A | DrugBank |
| IC50 (nM)*** | 6.8 nM (for binding to PBP1a of S. pneumoniae); 0.145 nM (for binding to PBP1b of S. pneumoniae); 2.4 nM (for binding to PBP2a of S. pneumoniae); 8.0 nM (for binding to PBP2b of S. pneumoniae); <0.037 nM (for binding to PBP3 of S. pneumoniae) | (Williamson et al., 1980) |
| Ki (µM) | N/A | N/A |
| Half-life (hrs) | 41-59 minutes | DrugBank |
| Duration of Action | 6-8 hours | FDA |
| Absorption Site | N/A | N/A |
| Transporter(s) | N/A | N/A |
| Metabolism | ~85% excreted unchanged by the kidneys over the course of 6 hours (minimal) | DrugBank |
| Excretion | ~ 85% excreted unchanged by the kidneys over the course of 6 hours (high urinary concentrations) cefoxitin passes into joint and pleural fluids and is detectable in antibacterial concentrations in bile | DrugBank |
| AMES Test (Carcinogenic Effect) | Probability 0.6912 (Non AMES toxic) | DrugBank |
| hERG Safety Test (Cardiac Effect) | Probability 0.9951 (weak inhibitor) | DrugBank |
| Liver Toxicity | In general, cephalosporins are associated with little hepatotoxicity. Cases of cephalosporin-induced liver injury have rarely been reported. | LiverTox |
Note: Parenteral administration of cephalosporins can result in minor elevations in serum aminotransferase and alkaline phosphatase values. However, these elevations are usually mild, asymptomatic, and do not cause more severe liver injury (LiverTox).
Drug Interactions and Side Effects
To ensure safety, patients should inform doctors if they have any of the following conditions before starting cefoxitin therapy: kidney disease, liver disease, stomach or intestinal disorder (ex. colitis), diabetes, congestive heart failure, malnutrition, cancer, very recent surgery and/or medical emergency. Certain conditions, such as inflammation of the large intestine and kidney disease associated with a reduction in kidney function, are contraindicated with this antibiotic (WebMD).
Table 4. Drug interactions and side effects of cefoxitin.
| Features | Comment(s) | Source |
|---|---|---|
| Total Number of Drug Interactions | 56 drugs | Drugs.com |
| Major Drug Interaction(s) | bcg (Tice BCG, Tice BCG Vaccine), cholera vaccine, live, typhoid vaccine, live | Drugs.com |
| Alcohol/Food Interaction(s) | Parenteral cefoxitin sodium contains about 53 mg of sodium per gram of cefoxitin activity. This sodium content should be taken into consideration when treating patients who have conditions, such as congestive heart failure, hypertension (high blood pressure), or fluid retention, which require sodium-restricted diets. | Drugs.com |
| Disease Interaction(s) | Pseudomembranous colitis (major), Renal Dysfunction (moderate), Hemodialysis (moderate), Liver disease (moderate), Seizure disorders (moderate) | Drugs.com |
| On-target Side Effects | Changes in skin color, pain and/or tenderness at the injection site, thrombophlebitis (inflammation of veins and swelling due to intravenous administration), superinfection | Drugs.com |
| Off-target Side Effects | Rash, nausea, vomiting, diarrhea, anaphylaxis, headache, dizziness, fever, hypotension, jaundice, vaginitis | Drugs.com |
| CYP Interactions | CYP450 3A4 substrate | DrugBank |
The most common side effects have been local reactions following intravenous administration of cefoxitin. Other adverse reactions have not been observed often, as cefoxitin is usually well tolerated. In addition, increased nephrotoxicity has been reported following concomitant administration of cephalosporins and aminoglycoside antibiotics (FDA, 2017).
Cases of Clostridium difficile associated diarrhea (CDAD) have been reported with the use of almost all antibacterial drugs, including cefoxitin, and may vary in severity from mild diarrhea to fatal colitis. CDAD occurs because treatment with antibiotics changes the normal bacterial flora of the colon, which results in an overgrowth of C. difficile (FDA, 2017).
Regulatory Approvals/Commercial
Cefoxitin, which was developed by Merck & Co., Inc., is sold under the commercial name Mefoxin® by Mylan Inc., and this product received US FDA approval on January 25th, 1993. Use of Mefoxin has been approved for (FDA, 2017):
- lower respiratory tract infections (including pneumonia and lung abscess)
- urinary tract infections
- intra-abdominal infections (including peritonitis and intra-abdominal abscess)
- gynecological infections (including endometritis, pelvic cellulitis, and pelvic inflammatory disease)
- septicemia
- bone and joint infection
- bone and joint infections
- skin and skin structure infections
- prophylaxis of infection (in the case of gastrointestinal surgery, vaginal hysterectomy, abdominal hysterectomy, or cesarean section)
Mefoxin is available as a powder (that contains about 53.8 mg of sodium per gram of cefoxitin activity) which must be mixed with a diluent before usage. The solution is then administered intravenously. Although the appropriate dosage should be determined based on the susceptibility of the pathogenic bacterial species, severity of the infection, and condition of the patient, the usual recommended adult dosage is 1 to 2 grams every 6 to 8 hours (FDA, 2017).
Links
Table 5: Links to resources to learn more about cefoxitin
| Comprehensive Antibiotic Resistance Database (CARD) | ARO: 0000008 |
| DrugBank | DB01331 |
| Drugs.com | https://www.drugs.com/mtm/cefoxitin.html |
| FDA - Mefoxin | https://www.accessdata.fda.gov/drugsatfda_docs/label/2017/050517s053lbl.pdf |
| LiverTox: National Institutes of Health (NIH) | https://www.ncbi.nlm.nih.gov/books/NBK548666/ |
| PubChem CID | 441199 |
Learn about cefoxitin resistance.
References
Cefoxitin - DrugBank. Drugbank.ca. https://www.drugbank.ca/drugs/DB01331
Cefoxitin. Drugs.com. https://www.drugs.com/mtm/cefoxitin.html
Cefoxitin. PubChem. https://pubchem.ncbi.nlm.nih.gov/compound/Cefoxitin
Cefoxitin Vial. WebMD. https://www.webmd.com/drugs/2/drug-18352/cefoxitin-intravenous/details/list-contraindications
Davies, C., White, S. W., Nicholas, R.A. (2000). Crystal Structure of a Deacylation-defective Mutant of Penicillin-binding Protein 5 at 2.3-Å Resolution. Journal of Biological Chemistry, 276, 616-623. https://doi.org/10.1074/jbc.m004471200
Jia, B., Raphenya, A. R., Alcock, B., Waglechner, N., Guo, P., Tsang, K. K., Lago, B. A., Dave, B. M., Pereira, S., Sharma, A. N., Doshi, S., Courtot, M., Lo, R., Williams, L. E., Frye, J. G., Elsayegh, T., Sardar, D. Westman, E. L., Pawlowski, A. C., Johnson, T. A., Brinkman, F. S., Wright, G. D., and McArthur, A. G. (2017) CARD 2017: expansion and model-centric curation of the Comprehensive Antibiotic Resistance Database. Nucleic Acids Research 45, D566-573. https://doi.org/10.1093/nar/gkw1004
LiverTox - Clinical and Research Information on Drug-Induced Liver Injury. National Institutes of Health. https://www.ncbi.nlm.nih.gov/books/NBK548666/
Mefoxin (Cefoxitin for Injection) (2017) Food and Drug Administration https://www.accessdata.fda.gov/drugsatfda_docs/label/2017/050517s053lbl.pdf
Nicholas, R. A., Krings, S., Tomberg, J., Nicola, G., and Davies, C. (2003). Crystal Structure of Wild-type Penicillin-binding Protein 5 from Escherichia coli. Journal of Biological Chemistry, 278, 52826-52833. https://doi.org/10.1074/jbc.m310177200 PDB ID: 1nzo
Nicola, G., Tomberg, J., Pratt, R. F., Nicholas, R. A., and Davies, C. (2010). Crystal Structures of Covalent Complexes of β-Lactam Antibiotics with Escherichia coli Penicillin-Binding Protein 5: Toward an Understanding of Antibiotic Specificity. Biochemistry, 49, 8094-8104. https://doi.org/10.1021/bi100879m PDB ID: 3mze
Sauvage, E., Kerff, F., Terrak, M., Ayala, J. A., and Charlier, P. (2008). The penicillin-binding proteins: structure and role in peptidoglycan biosynthesis. FEMS Microbiology Reviews, 32, 234-258. https://doi.org/10.1111/j.1574-6976.2008.00115.x
Williamson, R., Hakenbeck, R., and Tomasz, A. (1980). In vivo interaction of beta-lactam antibiotics with the penicillin-binding proteins of Streptococcus pneumoniae. Antimicrobial Agents and Chemotherapy, 18, 629-637. https://doi.org/10.1128/aac.18.4.629
March 2025, Gauri Patel, Helen Gao, Shuchismita Dutta; Reviewed by: Dr. Andrew Lovering
https://doi.org/10.2210/rcsb_pdb/GH/AMR/drugs/antibiotics/cellwall-biosynth/pbp/blm/cefoxitin
