Cefdinir

• Acute Bacterial Sinusitis
• Otitis Media (Ear Infections)
• Community-Acquired Pneumonia
• Pharyngitis and Tonsillitis

Cefdinir is a third-generation oral cephalosporin antibiotic used to treat various bacterial infections. This broad-spectrum antibiotic is particularly valuable for treating respiratory tract infections and skin infections in both adults and children due to its favorable dosing schedule and tolerability.

Mechanism of Action

Cefdinir, like other cephalosporins, is a beta-lactam antibiotic that works by inhibiting bacterial cell wall synthesis. It binds to penicillin-binding proteins (PBPs) and inhibits the transpeptidation step of peptidoglycan synthesis, which is essential for maintaining bacterial cell wall integrity. This leads to cell wall weakening, osmotic instability, and ultimately bacterial cell death. Cefdinir is bactericidal against susceptible organisms and has good activity against Gram-positive bacteria (including Staphylococcus aureus and Streptococcus species) and many Gram-negative bacteria (including Hemophilus influenzae and Moraxella catarrhalis).

Available Formulations

Cefdinir is available as oral capsules (300 mg) and as an oral suspension (125 mg/5 mL and 250 mg/5 mL). The capsules and suspension can be taken with or without food. The suspension should be shaken well before each use and stored in the refrigerator. After reconstitution, the suspension is stable for 10 days.

Medical Uses

Cefdinir is FDA-approved for the treatment of acute bacterial exacerbations of chronic bronchitis, acute maxillary sinusitis, community-acquired pneumonia, pharyngitis/tonsillitis, and uncomplicated skin and skin structure infections in adults and adolescents. In pediatric patients (6 months to 12 years), it is approved for acute bacterial otitis media, pharyngitis/tonsillitis, and uncomplicated skin infections. It is often used as a second-line agent when first-line antibiotics have failed or are contraindicated.

Dosing Guidelines

For adults and adolescents, the typical dose is 300 mg twice daily or 600 mg once daily for 5-10 days depending on the infection. For pediatric patients, dosing is based on weight: 7 mg/kg twice daily or 14 mg/kg once daily (maximum 600 mg/day). Duration varies: 10 days for pharyngitis/tonsillitis, 10 days for acute bacterial sinusitis, 5-10 days for pneumonia, 10 days for skin infections. Dose adjustment is required for patients with significant renal impairment (CrCl less than 30 mL/min).

Important Safety Information

Cefdinir is contraindicated in patients with known allergy to cephalosporins. Cross-reactivity with penicillins exists but is relatively low (approximately 1-2%). The medication should be used with caution in patients with a history of severe penicillin allergy (anaphylaxis). Clostridioides difficile-associated diarrhea (CDAD) has been reported with nearly all antibiotics and may range from mild diarrhea to fatal colitis. Patients should be monitored for diarrhea during and after treatment.

Drug Interactions

Antacids containing magnesium or aluminum and iron supplements can significantly reduce cefdinir absorption; these should be taken at least 2 hours before or after cefdinir. Iron-fortified infant formulas may also reduce absorption. Probenecid inhibits renal excretion of cefdinir, increasing plasma levels. Cefdinir may cause a false-positive reaction for urine glucose tests using Clinitest tablets and potentially false-positive direct Coombs tests.

Where Cefdinir Fits Among Oral Antibiotics

Cefdinir is prescribed more often than its evidence supports, and knowing why it was chosen matters. For most of its approved indications it is a second choice rather than a first one: amoxicillin or amoxicillin-clavulanate is preferred for bacterial sinusitis and for ear infection, and penicillin remains the reference treatment for streptococcal pharyngitis. Cefdinir becomes the reasonable option when there is a non-severe penicillin allergy, when a patient cannot tolerate the gastrointestinal effects of a higher-dose penicillin, or when once-daily dosing is what will actually get the course finished.

Its weakness is worth naming. Third-generation oral cephalosporins have less reliable activity against penicillin-resistant pneumococcus than high-dose amoxicillin does, so cefdinir is a poor choice for a patient who has already failed first-line therapy or who has risk factors for resistant organisms. And the more common problem is upstream of the drug entirely: most sinus congestion in the first week to ten days and almost all acute bronchitis are viral, and an antibiotic changes nothing except the side-effect risk and the resistance pressure. Where a skin infection needs oral treatment, cephalexin is usually the better-targeted cephalosporin.

Two Things Patients Call About

The first is red stool. Cefdinir combined with iron — an iron tablet, a multivitamin, or an iron-fortified formula in an infant — forms a non-absorbable complex that can turn the stool a striking brick red. It is harmless and it is not blood, but it alarms people, and it is worth mentioning at the counter rather than fielding as an emergency call. It is also a sign the two products are being taken too close together, which reduces how much antibiotic is absorbed; the separation described above applies to antacids as well.

The second is diarrhea. Loose stools during a course are common and usually settle, but diarrhea that is watery, frequent, bloody, or accompanied by fever and abdominal pain — during the course or in the weeks after it — needs to be reported rather than treated with an over-the-counter antidiarrheal, because it may represent a serious colitis. Courses are finished as prescribed rather than stopped when symptoms improve, and leftover antibiotic is not saved for the next illness. The MedlinePlus cefdinir monograph and the CDC guidance on antibiotic prescribing and use cover the drug and the decision to use one at all, and our antibiotic resistance guide explains why the question is asked every time.

Special Populations

Human data on cefdinir in pregnancy are limited but reassuring; it is used during pregnancy when clearly needed. It is excreted in human breast milk in small amounts and is generally considered compatible with breastfeeding. Safety and efficacy have been established in pediatric patients 6 months and older. Elderly patients may require dose adjustment if renal function is impaired. Dose reduction is recommended for patients with CrCl less than 30 mL/min (300 mg once daily for adults, 7 mg/kg once daily for children up to maximum 300 mg). Patients on hemodialysis should receive 300 mg or 7 mg/kg after each session.