Cefdinir (Omnicef) Dosage Calculator
Calculate cefdinir dosage for adults and children by weight and indication. Shows dose per administration, frequency, duration, and suspension volume for available formulations (125 mg/5 mL, 250 mg/5 mL). Includes renal dose adjustments and drug interaction guidance.
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Disclaimer: For educational purposes only. Not a substitute for clinical judgment. Always verify doses with current guidelines and pharmacy references.
About This Tool
What Is Cefdinir (Omnicef)?
Cefdinir is an oral third-generation cephalosporin antibiotic marketed under the brand name Omnicef. It has a broad spectrum of activity against gram-positive organisms (including penicillin-susceptible Streptococcus pneumoniae and Streptococcus pyogenes) and gram-negative organisms (including Haemophilus influenzae and Moraxella catarrhalis). It is commonly prescribed for respiratory tract infections, otitis media, sinusitis, pharyngitis, and uncomplicated skin and soft tissue infections in both adults and children aged 6 months and older.
How to Calculate Cefdinir Dose for Children
Pediatric cefdinir dosing is weight-based, expressed as mg/kg/day. The dose depends on the indication: for otitis media, sinusitis, and community-acquired pneumonia, the recommended dose is 14 mg/kg/day divided into two doses (7 mg/kg per dose, given every 12 hours). For pharyngitis/tonsillitis and skin infections, the dose is 7 mg/kg given twice daily. The maximum daily dose is 600 mg regardless of weight. Once you calculate the mg per dose, convert to mL based on the suspension concentration: mL = (mg per dose ÷ concentration mg per 5 mL) × 5.
Cefdinir vs Other Cephalosporins
Cefdinir offers once or twice daily dosing, a pleasant strawberry-flavored suspension, and does not require refrigeration after reconstitution (store at room temperature for up to 10 days). This makes it a convenient alternative to cephalexin (which requires TID or QID dosing) or amoxicillin-clavulanate (which can cause more GI side effects). However, cefdinir has limited activity against atypical organisms and anaerobes, and should not be used for complicated or deep-seated infections.
Important Drug Interactions
The most clinically significant interaction is with iron. Iron supplements, iron-containing multivitamins, and iron-fortified infant formulas substantially reduce cefdinir bioavailability. Iron-fortified formula can reduce absorption by approximately 80%. Separate cefdinir dosing from iron products by at least 2 hours. Aluminum- or magnesium-containing antacids similarly reduce absorption and should also be separated by 2 hours. This interaction also causes the characteristic reddish stool discoloration, which is benign but can alarm parents.
🔑 Clinical Pearls
- Red/reddish stools on cefdinir are not blood — they result from cefdinir–iron complexes in the GI tract. Always warn parents to expect this, especially if the child takes iron-fortified formula.
- Cefdinir is generally well-tolerated with a side effect profile comparable to other oral cephalosporins. Diarrhea (~8–15%) is the most common adverse effect.
- For patients with penicillin allergy, cefdinir is generally considered safe (cross-reactivity ~1–2% for 3rd-gen cephalosporins), but avoid in patients with a history of anaphylaxis to any beta-lactam.
- Renal dosing: Reduce to 300 mg/day (or 7 mg/kg/day for pediatrics) when CrCl <30 mL/min. For hemodialysis patients, give 300 mg QD and a supplemental dose after each session.
- Reconstituted suspension is stable for 10 days at room temperature — no refrigeration needed (though refrigeration is acceptable and may improve taste).
- Cefdinir does not cover MRSA, Pseudomonas aeruginosa, or atypical organisms (Mycoplasma, Chlamydia).
Key References
- Cefdinir (Omnicef) Prescribing Information. Abbvie Inc. (FDA-approved labeling).
- Lieberthal AS, et al. The diagnosis and management of acute otitis media. Pediatrics. 2013;131(3):e964–e999.
- Wald ER, et al. Clinical practice guideline for the diagnosis and management of acute bacterial sinusitis in children. Pediatrics. 2013;132(1):e262–e280.
- Shulman ST, et al. Clinical practice guideline for the diagnosis and management of group A streptococcal pharyngitis. Clin Infect Dis. 2012;55(10):e86–e102.
- Red Book: 2021 Report of the Committee on Infectious Diseases. American Academy of Pediatrics.
Formula last verified: February 2026