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Cefdinir

Cefdinir: A Potent Oral Cephalosporin for Respiratory and Skin Infections

Introduction

Cefdinir is a third-generation oral cephalosporin antibiotic belonging to the broader beta-lactam family. Approved by the FDA in 1997, Cefdinir is widely used in the outpatient setting to treat a variety of mild to moderate bacterial infections, particularly of the respiratory tract and skin. Its broad spectrum of activity, combined with good oral bioavailability and tolerability, makes it a valuable choice in clinical practice.

Cefdinir

  • Class: Third-generation cephalosporin

  • Brand Names: Omnicef (discontinued in some markets), generics available

  • Route of Administration: Oral (capsule and suspension)

  • Chemical Formula: C14H13N5O5S2

  • Molecular Weight: 395.42 g/mol

Cefdinir is designed for outpatient use, especially as an alternative to injectable third-generation cephalosporins like ceftriaxone.

Mechanism of Action

Cefdinir, like other beta-lactam antibiotics, works by inhibiting bacterial cell wall synthesis. It binds to penicillin-binding proteins (PBPs) involved in the cross-linking of peptidoglycan layers, a crucial step in bacterial cell wall construction. The inhibition leads to weakened walls, osmotic instability, and eventual bacterial death.

Cefdinir is bactericidal and its killing activity is time-dependent, meaning it is most effective when concentrations are maintained above the minimum inhibitory concentration (MIC) for the target pathogen.

Spectrum of Antibacterial Activity

As a third-generation cephalosporin, Cefdinir offers enhanced activity against Gram-negative bacteria while maintaining some Gram-positive coverage.

Gram-Positive Bacteria

  • Streptococcus pneumoniae (including some penicillin-resistant strains)

  • Streptococcus pyogenes

  • Staphylococcus aureus (methicillin-sensitive strains only)

Gram-Negative Bacteria

  • Haemophilus influenzae

  • Moraxella catarrhalis

  • Escherichia coli (non-ESBL-producing)

  • Klebsiella pneumoniae

  • Proteus mirabilis

Limited or No Activity

  • MRSA

  • Pseudomonas aeruginosa

  • Enterococcus species

  • Anaerobes

Cefdinir is not suitable for hospital-acquired infections or infections involving resistant Gram-negative pathogens.

Pharmacokinetics and Pharmacodynamics

Cefdinir exhibits favorable pharmacokinetic properties for outpatient therapy.

Parameter Value
Oral Bioavailability ~16–25% (affected by food)
Peak Plasma Concentration ~2–4 hours
Half-Life ~1.7 hours
Protein Binding ~60–70%
Elimination Primarily renal (urine)

Food can reduce the absorption of Cefdinir by approximately 15–20%. Thus, it is typically recommended to be taken on an empty stomach or at least 2 hours apart from iron or antacids.

Formulations and Dosing

Cefdinir is available in:

  • Capsules: 300 mg

  • Oral Suspension: 125 mg/5 mL, 250 mg/5 mL

Adult Dosing

  • Typical: 300 mg twice daily or 600 mg once daily for 5–10 days depending on the infection

Pediatric Dosing

  • 14 mg/kg/day in one or two divided doses

  • Maximum daily dose: 600 mg

Clinical Indications

Cefdinir is FDA-approved for the treatment of several infections and is often used as an alternative to amoxicillin-clavulanate or macrolides.

1. Acute Bacterial Otitis Media

  • Especially in children

  • Effective against H. influenzae and M. catarrhalis

2. Acute Exacerbations of Chronic Bronchitis

  • For patients with underlying COPD or asthma

  • Targets respiratory pathogens like H. influenzae

3. Pharyngitis and Tonsillitis

  • Alternative to penicillin or amoxicillin

  • Especially for Streptococcus pyogenes

4. Community-Acquired Pneumonia (CAP)

  • Mild-to-moderate cases

  • Treats susceptible strains of S. pneumoniae

5. Sinusitis

  • Empirical treatment of acute maxillary sinusitis

6. Uncomplicated Skin and Soft Tissue Infections

  • Cellulitis

  • Impetigo

  • Folliculitis caused by MSSA or S. pyogenes

Clinical Efficacy

Numerous clinical trials have validated Cefdinir’s efficacy, particularly in pediatric and respiratory tract infections. Comparative studies show:

  • Comparable cure rates to amoxicillin-clavulanate in otitis media and sinusitis

  • Equivalent to cefuroxime in treating CAP

  • More tolerable than erythromycin and clarithromycin in terms of GI side effects

Adverse Effects

Cefdinir is generally well tolerated, but some adverse effects may occur.

Common Side Effects

  • Diarrhea (especially in children)

  • Nausea and vomiting

  • Headache

  • Rash

Notable Adverse Effects

  • Red stools in children (especially with iron co-administration; benign)

  • Hypersensitivity reactions, including urticaria and anaphylaxis

  • Clostridioides difficile-associated diarrhea (CDAD)

Drug Interactions

Cefdinir interacts with some commonly used medications and supplements:

  • Iron Supplements: Reduce Cefdinir absorption; separate doses by 2 hours

  • Antacids: May decrease bioavailability; avoid concurrent use

  • Probenecid: Inhibits renal clearance and increases serum levels

Use in Special Populations

Pediatrics

  • Widely used and well tolerated

  • Preferred in children who cannot tolerate amoxicillin

Pregnancy and Lactation

  • Category B

  • No known teratogenicity

  • Minimal transfer into breast milk; generally considered safe

Geriatrics

  • Safe in elderly but adjust dose in renal impairment

Renal Impairment

  • Reduce dosing frequency if creatinine clearance <30 mL/min

Antibiotic Resistance and Stewardship

Cefdinir, like all cephalosporins, faces challenges from evolving resistance patterns. Mechanisms include:

  • Beta-lactamase production (e.g., ESBLs)

  • Altered PBPs (e.g., penicillin-resistant S. pneumoniae)

  • Efflux mechanisms

Because of its limited anaerobic and Pseudomonas activity, Cefdinir does not encourage resistance in broader microbiota, making it a reasonable choice for narrow-spectrum use.

Stewardship Considerations

  • Use for confirmed or suspected susceptible pathogens

  • Avoid overuse in viral infections

  • Prefer cultures and sensitivity testing in recurrent or treatment-resistant cases

Comparative Analysis with Other Oral Cephalosporins

Drug Generation Dosing Gram-Negative Activity GI Side Effects
Cefdinir 3rd BID/OD Good Mild
Cefuroxime 2nd BID Moderate Mild–Moderate
Cephalexin 1st QID Poor Minimal
Cefixime 3rd OD Excellent Mild–Moderate

Cefdinir’s balance of Gram-positive and Gram-negative coverage, coupled with oral convenience, places it favorably in outpatient care.

Market Availability

Cefdinir is widely available globally under generic labels after the expiration of Omnicef’s patent. It is especially popular in:

  • North America

  • Japan

  • Latin America

  • Some parts of Asia

Although Omnicef is no longer marketed in the U.S., generics remain widely prescribed.

Patient Counseling Tips

  • Take the medication with or without food, but avoid iron and antacids near the time of dosing.

  • Complete the full course, even if symptoms improve early.

  • Be aware of possible reddish stool in children; this is harmless.

  • Store oral suspension as instructed (often at room temperature after reconstitution) and shake well before use.

Conclusion

Cefdinir continues to be a reliable and effective oral antibiotic for treating respiratory tract infections, sinusitis, skin infections, and pediatric illnesses. Its safety profile, dosing flexibility, and broad antimicrobial spectrum make it a versatile tool in outpatient antibiotic therapy.