Introduction
Cefdinir is a semi-synthetic, broad-spectrum third-generation cephalosporin antibiotic approved by the FDA in 1997. It belongs to the beta-lactam class of antibiotics and is commonly prescribed for various bacterial infections due to its favorable safety profile and oral bioavailability. Cefdinir is marketed under brand names including Omnicef and is available as capsules and oral suspension.
Mechanism of Action
Cefdinir exerts its bactericidal effects by inhibiting bacterial cell wall synthesis through binding to penicillin-binding proteins (PBPs). Like other beta-lactam antibiotics, it disrupts the final transpeptidation step of peptidoglycan synthesis in bacterial cell walls, leading to cell lysis and death. Cefdinir demonstrates enhanced stability against many beta-lactamases compared to earlier cephalosporins, particularly those produced by Gram-negative bacteria.
Indications
FDA-approved indications include:
- Community-acquired pneumonia caused by Haemophilus influenzae, Haemophilus parainfluenzae, Streptococcus pneumoniae (penicillin-susceptible strains only)
- Acute exacerbations of chronic bronchitis caused by H. influenzae, H. parainfluenzae, Moraxella catarrhalis, and S. pneumoniae
- Acute maxillary sinusitis caused by H. influenzae, M. catarrhalis, and S. pneumoniae
- Pharyngitis/Tonsillitis caused by Streptococcus pyogenes
- Uncomplicated skin and skin structure infections caused by Staphylococcus aureus (including beta-lactamase producing strains) and S. pyogenes
Dosage and Administration
Adults and adolescents (13 years and older):- Community-acquired pneumonia: 300 mg every 12 hours for 10 days
- Acute exacerbations of chronic bronchitis: 300 mg every 12 hours for 5-10 days
- Acute maxillary sinusitis: 300 mg every 12 hours or 600 mg every 24 hours for 10 days
- Pharyngitis/Tonsillitis: 300 mg every 12 hours or 600 mg every 24 hours for 5-10 days
- Skin and skin structure infections: 300 mg every 12 hours or 600 mg every 24 hours for 10 days
- 7 mg/kg every 12 hours or 14 mg/kg every 24 hours
- Maximum daily dose: 600 mg
- CrCl <30 mL/min: 300 mg once daily
- Hemodialysis: 300 mg or 7 mg/kg after each dialysis
Administration: May be taken with or without food. Oral suspension should be shaken well before use.
Pharmacokinetics
Absorption: Well-absorbed from GI tract; bioavailability approximately 21-25% (dose-dependent). Food delays absorption but does not significantly affect total bioavailability. Distribution: Widely distributed into body tissues and fluids. Protein binding: 60-70%. Crosses placental barrier and enters breast milk. Metabolism: Minimally metabolized in liver. Elimination: Primarily excreted unchanged in urine (60-70% within 24 hours). Half-life: 1.7-2 hours in normal renal function; prolonged in renal impairment.Contraindications
- Known hypersensitivity to cefdinir or other cephalosporins
- Patients with history of severe hypersensitivity reactions to penicillins or other beta-lactam antibiotics (cross-reactivity may occur)
- History of cephalosporin-associated hemolytic anemia
Warnings and Precautions
- Clostridium difficile-associated diarrhea: May range from mild diarrhea to fatal colitis
- Hypersensitivity reactions: Serious anaphylactic reactions possible
- Direct Coombs test seroconversion: May occur during therapy
- Renal impairment: Dosage adjustment required
- Seizure potential: Especially in patients with renal impairment
- Superinfection: Possible emergence of resistant organisms
- Phenylketonurics: Oral suspension contains phenylalanine (5 mg per mL)
- Iron absorption: May be impaired; separate administration from iron-containing products
Drug Interactions
- Antacids containing magnesium or aluminum: Reduce absorption; administer at least 2 hours apart
- Iron supplements and iron-fortified foods: Reduce absorption; administer at least 2 hours apart
- Probenecid: May increase cefdinir concentrations
- Warfarin: Possible enhancement of anticoagulant effect (monitor INR)
- Live bacterial vaccines: Antibiotics may interfere with vaccine efficacy
Adverse Effects
Common (≥1%):- Diarrhea (15%)
- Vaginal moniliasis (3%)
- Nausea (3%)
- Headache (2%)
- Abdominal pain (1%)
- Pseudomembranous colitis
- Anaphylaxis
- Stevens-Johnson syndrome
- Toxic epidermal necrolysis
- Hemolytic anemia
- Hepatitis
- Acute renal failure
- Seizures
Monitoring Parameters
- Clinical response to therapy
- Signs of hypersensitivity reactions
- Diarrhea (monitor for C. difficile)
- Complete blood count (especially with prolonged therapy)
- Renal function (in patients with renal impairment)
- Liver function tests (with prolonged therapy)
- Coombs test if hemolytic anemia suspected
- INR in patients on warfarin
Patient Education
- Complete full course of therapy even if feeling better
- Take as directed, with or without food
- Separate administration from antacids or iron products by at least 2 hours
- Report severe diarrhea, abdominal pain, or blood/mucus in stool
- Report rash, hives, or difficulty breathing immediately
- Oral suspension may be stored at room temperature for 10 days
- Inform all healthcare providers of cefdinir use
- Use additional contraception if taking oral contraceptives (potential reduced efficacy)
- Do not share medication with others
References
1. FDA Prescribing Information: Omnicef (cefdinir) 2. Gilbert DN, et al. The Sanford Guide to Antimicrobial Therapy. 52nd edition 3. Lexicomp Online: Cefdinir Monograph 4. Clinical Pharmacology [Internet]. Tampa (FL): Elsevier 5. Mandell, Douglas, and Bennett's Principles and Practice of Infectious Diseases. 9th edition 6. Nahata MC. Pharmacokinetics of cefdinir in pediatric patients. Antimicrob Agents Chemother. 1995 7. Guay DR. Cefdinir: an advanced-generation, broad-spectrum oral cephalosporin. Clin Ther. 2002
Note: This information is for educational purposes only and does not replace professional medical advice. Always consult a healthcare provider for medical guidance.