CEFDINIR
Clinical safety rating: safe
Human studies have proved safety
Cefdinir is a third-generation cephalosporin antibiotic that inhibits bacterial cell wall synthesis by binding to penicillin-binding proteins (PBPs), thereby inhibiting peptidoglycan cross-linking, leading to cell lysis and death.
| Metabolism | Cefdinir is not significantly metabolized; it is primarily excreted unchanged in the urine via tubular secretion and glomerular filtration. Minimal renal metabolism occurs. |
| Excretion | Renal: 90-95% unchanged in urine via glomerular filtration and tubular secretion. Biliary/fecal: <1% biliary, <5% fecal. |
| Half-life | Terminal elimination half-life: 1.7 ± 0.6 hours (range 1.4-2.3 h) in healthy adults; prolonged in renal impairment (e.g., up to 8 hours in end-stage renal disease). |
| Protein binding | ~60-70% bound to plasma proteins (primarily albumin). |
| Volume of Distribution | Vd: 0.35 ± 0.12 L/kg (approximately 24 L in adults), indicating distribution primarily into extracellular fluid. |
| Bioavailability | Oral: 16-25% (mean ~20%) after capsule; 91% for suspension due to slower gastric emptying; absorption increased with food; no IV formulation. |
| Onset of Action | Oral: peak serum concentrations at 2-4 hours; time to clinical effect typically within 24 hours for susceptible infections. |
| Duration of Action | Duration ~12 hours; recommended dosing every 12 hours to maintain therapeutic levels above MIC for susceptible pathogens. |
300 mg orally twice daily for 5-10 days, or 600 mg orally once daily for 10 days.
| Dosage form | FOR SUSPENSION |
| Renal impairment | For CrCl 30-59 mL/min: 300 mg twice daily or 600 mg once daily. For CrCl <30 mL/min or hemodialysis: 300 mg once daily or 7 mg/kg once daily (max 300 mg). For peritoneal dialysis: 300 mg once daily. |
| Liver impairment | No dose adjustment required for hepatic impairment as cefdinir is primarily excreted renally. |
| Pediatric use | For children 6 months to 12 years: 7 mg/kg orally every 12 hours or 14 mg/kg orally once daily for 5-10 days (max 600 mg/day). For acute bacterial otitis media and acute maxillary sinusitis: 7 mg/kg every 12 hours for 5-10 days. |
| Geriatric use | Dose adjustment based on renal function; monitor CrCl and reduce dose accordingly. No specific geriatric dose changes aside from renal considerations. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Antacids and iron supplements decrease absorption May cause red stools due to interaction with iron.
| Breastfeeding | Excreted in breast milk in low concentrations. M/P ratio not established. Consider risks vs benefits; monitor infant for diarrhea or rash. |
| Teratogenic Risk | FDA Pregnancy Category B. No evidence of teratogenicity in animal studies. Insufficient human data; use only if clearly needed. Avoid in first trimester unless essential. |
| Fetal Monitoring |
■ FDA Black Box Warning
No FDA black box warning.
| Common Effects | Diarrhea |
| Serious Effects |
["Absolute: Known hypersensitivity to cefdinir or other cephalosporins.","Relative: History of immediate-type hypersensitivity to penicillins (possible cross-reactivity).","Anaphylactic reaction to any beta-lactam antibiotic."]
| Precautions | ["Hypersensitivity reactions (anaphylaxis, Stevens-Johnson syndrome) have been reported; discontinue cefdinir if an allergic reaction occurs.","Clostridioides difficile-associated diarrhea (CDAD) may occur; consider if diarrhea develops.","Dose adjustment required in renal impairment (CrCl <30 mL/min).","May cause seizure activity in patients with renal impairment or CNS disorders.","Prolonged use may result in superinfection."] |
| Food/Dietary |
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| No specific monitoring required beyond standard pregnancy care. Monitor for maternal adverse effects (GI disturbances, rash) and fetal wellbeing via routine ultrasound. |
| Fertility Effects | No known adverse effects on fertility in animal studies. Human data lacking. |
| Avoid concurrent administration with iron supplements, iron-fortified infant formula, or multivitamins containing iron, as they reduce cefdinir absorption by up to 80%. Separate by at least 2 hours. Antiulcer drugs (e.g., antacids containing magnesium or aluminum) may also reduce absorption, so take cefdinir 2 hours before or after such products. |
| Clinical Pearls | Cefdinir is a third-generation oral cephalosporin with activity against many Gram-positive and Gram-negative organisms. It is FDA-approved for acute otitis media, community-acquired pneumonia, acute sinusitis, pharyngitis/tonsillitis, and uncomplicated skin and soft tissue infections. Note that cefdinir may cause a false-positive urine glucose test (Clinitest) but not with glucose oxidase methods. It can also cause harmless red stools due to non-absorbable cefdinir-iron complex. Patients with penicillin allergy may have cross-reactivity, so use caution. Dose adjustment is required for creatinine clearance <30 mL/min (300 mg once daily instead of standard dosing). |
| Patient Advice | Take cefdinir exactly as prescribed, with or without food; but avoid taking with iron supplements or iron-fortified foods within 2 hours as it reduces absorption. · Complete the full course even if you feel better to prevent resistance. · You may experience mild diarrhea (common), but contact your doctor if severe watery stools, abdominal pain, or fever occurs (possible C. difficile). · Cefdinir can cause a harmless red or orange discoloration of stools; this is not blood. · Inform your doctor if you have a history of penicillin allergy or kidney problems. · Do not use cefdinir if you are allergic to cephalosporins or penicillins. |