Cefixime
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Here is a complete pharmacological profile of Cefixime drawn from authoritative textbooks:
Cefixime
Drug Class
Cefixime is a third-generation oral cephalosporin (beta-lactam antibiotic). It is one of the few third-generation cephalosporins available in oral form.
Mechanism of Action
Like all beta-lactams, cefixime acts by binding to penicillin-binding proteins (PBPs) on bacterial cell walls, inhibiting transpeptidation and cross-linking of peptidoglycan. This disrupts cell wall synthesis and leads to bacterial cell lysis (bactericidal).
Antimicrobial Spectrum
Third-generation cephalosporins are generally less active against gram-positive cocci than first-generation agents, but much more active against gram-negative Enterobacterales. Cefixime specifically covers:
- Gram-negative: E. coli, Proteus mirabilis, H. influenzae (including ampicillin-resistant strains), N. gonorrhoeae, S. pyogenes (Group A Strep)
- Gram-positive: Streptococcus pyogenes (pharyngitis)
- Not active against: Staphylococcus aureus (MRSA or MSSA), penicillin-resistant S. pneumoniae, Pseudomonas aeruginosa, Bacteroides fragilis, anaerobes
Resistance is increasing due to ESBL-producing strains - Goodman & Gilman's, p. 1177
Pharmacokinetics
| Parameter | Details |
|---|---|
| Route | Oral (capsule, tablet, suspension) |
| Bioavailability | Moderate (tablets have reduced bioavailability vs. suspension) |
| Half-life (t½) | 3 to 4 hours |
| Protein binding | Moderate |
| Distribution | Good tissue penetration |
| Metabolism | Minimal hepatic metabolism |
| Excretion | Urine (50%, unchanged) + bile (5-10%) - unlike most cephalosporins which are primarily renal |
- Goodman & Gilman's Pharmacological Basis of Therapeutics, p. 1177
- Harriet Lane Handbook, 23rd ed.
Formulations (Preparations)
- Oral suspension: 100 mg/5 mL, 200 mg/5 mL, 500 mg/5 mL
- Chewable tablets: 100 mg, 200 mg (contain aspartame)
- Capsules: 400 mg
Doses
Children (>6 months):
- Standard: 8 mg/kg/day divided every 12-24 hours PO; max 400 mg/day
- Acute UTI (alternative): 16 mg/kg/day divided every 12 hours on Day 1, then 8 mg/kg/day every 24 hours for 13 more days; max 400 mg/day
Adolescents and Adults:
- 400 mg/day (as a single daily dose or divided every 12 hours PO)
- Standard course: 5 to 7 days (longer for S. pyogenes infections)
Gonorrhea (when ceftriaxone unavailable):
-
800 mg single oral dose + doxycycline 100 mg PO BID x 7 days
-
Harriet Lane Handbook, 23rd ed., p. 5116-5122
Clinical Indications
- Urinary tract infections - caused by E. coli and P. mirabilis
- Otitis media - caused by H. influenzae and S. pyogenes (use suspension, not tablets)
- Pharyngitis/Tonsillitis - due to S. pyogenes
- Uncomplicated gonorrhea (cervical, urethral, rectal) - only when ceftriaxone is unavailable; no longer CDC first-line due to rising resistance
- Typhoid fever - used in multidrug-resistant (MDR) typhoid (mentioned in Park's Textbook of Preventive Medicine)
- Respiratory tract infections - limited use; cannot reliably cover penicillin-resistant pneumococci
Gonorrhea: Important Resistance Note
The CDC no longer recommends cefixime as a routine first-line agent for gonorrhea. Treatment failures have been reported in Asia, Europe, South Africa, Canada, and Australia. Intramuscular ceftriaxone is preferred because it achieves higher bactericidal serum concentrations. Cefixime is reserved for situations where ceftriaxone is unavailable.
- Smith and Tanagho's General Urology, 19th ed.
- Yamada's Textbook of Gastroenterology, 7th ed.
Adverse Effects
| Effect | Details |
|---|---|
| GI disturbances | Diarrhea (16% incidence in clinical trials), abdominal pain, nausea |
| Headache | Commonly reported |
| Transient hepatotoxicity | Transient rise in AST/ALT |
| Hypersensitivity | Cross-reactivity with penicillin allergy (use with caution) |
Drug Interactions
- Probenecid - increases serum cefixime levels (blocks renal tubular secretion)
- Carbamazepine - cefixime may increase carbamazepine serum concentrations (monitor)
Lab Interference
- False positive urine-reducing substance tests (Clinitest, Benedict's solution, Fehling's solution)
- False positive Coombs test
- False positive nitroprusside test for ketones
- Use enzymatic glucose oxidase tests (Clinistix, Tes-Tape) instead of copper-reduction tests
Special Populations
| Population | Consideration |
|---|---|
| Renal impairment | Dose reduction required |
| Penicillin allergy | Use with caution (cross-reactivity possible) |
| Pregnancy | No association with congenital abnormalities seen in large studies (cephalosporins generally considered safe) - Dermatology 2-Volume Set 5e |
| Otitis media in children | Use suspension; tablets have reduced bioavailability and are not recommended for this indication |
Key Points to Remember
- Only oral third-generation cephalosporin commonly used clinically
- Excreted in both urine AND bile (unlike most cephalosporins - renal only)
- No antistaphylococcal activity; no anti-pseudomonal activity
- Activity against penicillin-resistant pneumococci is inadequate
- Preferred for gram-negative UTIs and streptococcal pharyngitis as an oral step-down agent
- No longer CDC-recommended first-line for gonorrhea due to rising resistance
Sources: Goodman & Gilman's Pharmacological Basis of Therapeutics, 13th ed. | Harriet Lane Handbook, 23rd ed. | Smith and Tanagho's General Urology, 19th ed. | Park's Textbook of Preventive and Social Medicine
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