Cefixime | Pharmacology Mentor

Generic Name

Cefixime

Inhibition of bacterial cell‑wall synthesis
Binds to penicillin‑binding proteins (PBPs) on the bacterial cell membrane.
Prevents cross‑linking of the peptidoglycan layer → cell lysis and death.
Broad activity against Gram‑negative organisms (e.g., *Escherichia coli, Klebsiella, Haemophilus*).
Moderate activity against Gram‑positive cocci (e.g., *Streptococcus pneumoniae*).
Low cross‑reactivity with first‑generation cephalosporins (lower risk of severe allergic reactions).

Absorption: ~80–90 % orally, rapid with peak serum levels at 1–2 h.
Protein binding: ~30 % (moderate).
Metabolism: Minimal hepatic metabolism; largely excreted unchanged.
Excretion: 30 % renal, 70 % biliary (in most patients).
Half‑life: 4–6 h (allowing once‑daily dosing).
Adjustments: Reduce dose in mild‑to‑moderate renal impairment (CrCl >30 mL/min). No dose adjustment for hepatic impairment.

Hypersensitivity to cephalosporins, penicillins, or other β‑lactams.
Severe renal failure (CrCl <30 mL/min) – dose reduction required.
Pregnancy: Category C; limited safety data – use only if benefits outweigh risks.
Lactation: Category B; excreted in milk – consult guidelines.
Concurrent use of rifampin (increases cefixime clearance, reduces efficacy).
G6PD deficiency: Potential hemolysis; monitor for signs.
Pediatric dosage limited to 6 months–12 yrs; caution in infants, especially <3 months.

Adults (≥16 yrs)
Mild–moderate infections: 400 mg once daily (or 200 mg twice daily).
Severe infections (including gonorrhea): 400 mg twice daily for 10–14 days (gonorrhea: 400 mg BID for 3 days).
Elderly (≥65 yrs): same as adults; monitor renal function.
Infants/Children (≥6 mos)
10 mg/kg (max 400 mg) once daily (for UTI).
Bronchial infections: same dosing, duration 10–14 days.
Administration: Oral tablets or drops; can be taken with or without food.
Patient counselling: Take 30‑60 min before/after food to maximize absorption.

Class	Common	Serious
GI	Nausea, vomiting, diarrhea, abdominal discomfort, dysosmia (taste disturbance)	Severe, persistent diarrhea (including C. difficile colitis)
Allergic	Rash, pruritus, urticaria	Anaphylaxis, angioedema, Stevens–Johnson syndrome
Hematologic	None	Hemolysis (especially in G6PD deficiency)
Renal	None	Acute interstitial nephritis, nephrolithiasis
Other	None	Encephalopathy in severe renal impairment

Renal function: baseline serum creatinine & CrCl; repeat at week 1 if prolonged therapy.
Pregnancy: early ultrasound if prolonged use.
Signs of allergic reaction: monitor closely after first few doses.
G6PD status: test if family history or hemolytic anemias.
Adherence log: encourage daily dosing for adequate serum levels.

Outpatient gonorrhea therapy: Cefixime 400 mg BID for 3 days is now first‑line where penicillin/ceftazidime resistance is high; avoid after reporting *C. trachomatis* coinfection.
Azithromycin synergy: Use cefixime + azithromycin for respiratory infections caused by atypical organisms (e.g., *Mycoplasma*, *Chlamydophila*) to cover both typical and atypical pathogens.
Taste disturbance: Most patients forget to rinse; advise soft food or open mouth after dose.
Prenatal use: Category C; if used during pregnancy, switch to ampicillin/amoxicillin when gestational age <20 weeks or consider cefalexin.
Avoid in severe renal impairment: 400 mg BID leads to supratherapeutic levels. Withdrawal of dose to 200 mg BID recommended when CrCl 15–30 mL/min.
Pharmacy timing: Because oral absorption is best in a fasted state, ask patients to take cefixime 30 min before breakfast or after dinner with water; a recent study showed a ~10 % increase in Cmax.
Combination with rifampin: The CYP3A4 induction by rifampin increases cefixime clearance by ~60 %; use alternative antibiotics in TB co‑therapy.
Re‑dosage after missed doses: Skip if more than 28 h between doses—restart the regimen.

*Data backed by FDA label, WHO guidelines, and current peer‑reviewed literature.*