Cefdinir Dosage Calculator

What Is Cefdinir (Omnicef)?

Cefdinir is a third-generation oral cephalosporin antibiotic sold under the brand name Omnicef. It works by inhibiting bacterial cell wall synthesis, making it effective against a wide range of gram-positive and gram-negative bacteria. Cefdinir is commonly prescribed for respiratory tract infections, ear infections, sinusitis, and skin infections.

As a cephalosporin, cefdinir belongs to the beta-lactam family of antibiotics. It is bactericidal, meaning it kills bacteria rather than simply inhibiting their growth. Its broad-spectrum activity makes it a popular choice in both adult and pediatric medicine.

Cefdinir Dosage for Adults

For adults and adolescents aged 13 years and older, cefdinir is available as 300 mg capsules. The standard adult dosages are:

Indication	Dose	Frequency	Duration
Community-Acquired Pneumonia	300 mg	Every 12 hours	10 days
Acute Exacerbation of Chronic Bronchitis	300 mg	Every 12 hours	5–10 days
Acute Exacerbation of Chronic Bronchitis (alt)	600 mg	Every 24 hours	10 days
Acute Maxillary Sinusitis	300 mg	Every 12 hours	10 days
Acute Maxillary Sinusitis (alt)	600 mg	Every 24 hours	10 days
Pharyngitis / Tonsillitis	300 mg	Every 12 hours	5–10 days
Pharyngitis / Tonsillitis (alt)	600 mg	Every 24 hours	10 days
Uncomplicated Skin Infections	300 mg	Every 12 hours	10 days

The maximum adult daily dose is 600 mg. All adult doses are fixed (not weight-based).

Pediatric Cefdinir Dosage

For children aged 6 months to 12 years, cefdinir dosing is weight-based and typically administered as an oral suspension:

Indication	Dose	Frequency	Duration
Acute Otitis Media	7 mg/kg	Every 12 hours	5–10 days
Acute Otitis Media (alt)	14 mg/kg	Every 24 hours	10 days
Acute Maxillary Sinusitis	7 mg/kg	Every 12 hours	10 days
Acute Maxillary Sinusitis (alt)	14 mg/kg	Every 24 hours	10 days
Pharyngitis / Tonsillitis	7 mg/kg	Every 12 hours	5–10 days
Pharyngitis / Tonsillitis (alt)	14 mg/kg	Every 24 hours	10 days
Uncomplicated Skin Infections	7 mg/kg	Every 12 hours	10 days

The maximum pediatric daily dose is 600 mg, regardless of weight. For children weighing more than about 43 kg, adult doses should be used instead.

Suspension Concentrations

Cefdinir oral suspension is available in two concentrations:

• 125 mg / 5 mL — lower concentration, easier to measure small doses
• 250 mg / 5 mL — higher concentration, smaller volumes for older/heavier children

The suspension should be shaken well before each use and can be mixed with food if needed. Store reconstituted suspension at room temperature and discard after 10 days.

How to Calculate Cefdinir Dosage

Step-by-Step Pediatric Calculation

1. Convert weight to kilograms if needed (1 lb = 0.4536 kg)
2. Choose dosing frequency:
   • Twice daily: multiply weight by 7 mg/kg
   • Once daily: multiply weight by 14 mg/kg
3. Cap at maximum: Single dose cannot exceed 300 mg (BID) or 600 mg (QD), and total daily dose must not exceed 600 mg
4. Calculate suspension volume:
   Volume (mL) = Dose (mg) ÷ Concentration (mg/mL)

Example: A 20 kg child with an ear infection, dosed twice daily:
Dose = 20 kg × 7 mg/kg = 140 mg per dose
Using 125 mg/5 mL suspension: Volume = 140 ÷ 25 = 5.6 mL per dose
Daily total = 140 × 2 = 280 mg/day

Important Safety Information

Contraindications

• Known allergy to cefdinir or other cephalosporins
• History of severe allergic reaction (anaphylaxis) to any beta-lactam antibiotic

Drug Interactions

• Iron supplements & antacids — reduce cefdinir absorption; take cefdinir at least 2 hours before or after iron-containing products
• Probenecid — may increase cefdinir blood levels
• Iron-fortified infant formula may cause reddish stools (harmless but alarming to parents)

Renal Impairment

For patients with creatinine clearance <30 mL/min, the dose should be reduced to 300 mg once daily (adults) or 7 mg/kg once daily (children). Patients on hemodialysis should receive 300 mg or 7 mg/kg after each session.

Cefdinir vs Other Antibiotics

Feature	Cefdinir	Amoxicillin	Azithromycin
Generation	3rd-gen cephalosporin	Aminopenicillin	Macrolide
Spectrum	Broad (gram +/-)	Broad (gram +/-)	Broad + atypicals
Typical course	5–10 days	7–10 days	3–5 days
Pediatric form	Suspension	Suspension	Suspension
Common use	2nd line therapy	1st line therapy	Penicillin allergy

Common Side Effects

• Diarrhea (up to 15% of patients)
• Nausea and vomiting
• Abdominal pain
• Vaginal candidiasis (yeast infection)
• Headache
• Reddish-colored stools (especially with iron-containing products — harmless)
• Rash (discontinue and contact physician if severe)

Frequently Asked Questions

Can I drink alcohol while taking cefdinir?

While cefdinir does not have the same disulfiram-like reaction seen with some cephalosporins (like cefotetan), combining antibiotics with alcohol is generally discouraged. Alcohol can worsen gastrointestinal side effects like nausea and diarrhea, and may impair immune function during recovery.

Does cefdinir affect birth control pills?

Antibiotics including cefdinir may theoretically reduce the effectiveness of oral contraceptives by altering gut flora that help reactivate ethinyl estradiol. While evidence is limited, some healthcare providers recommend using backup contraception during antibiotic therapy.

What if I miss a dose?

Take the missed dose as soon as you remember. If it is almost time for the next dose, skip the missed dose and continue with the regular schedule. Do not double the dose to make up for a missed one.

How should I store cefdinir suspension?

Store reconstituted suspension at room temperature (20–25°C / 68–77°F). Do not refrigerate. Shake well before each use. Discard any unused suspension after 10 days.

Can cefdinir be used in infants under 6 months?

Cefdinir is not FDA-approved for infants younger than 6 months. Safety and efficacy have not been established in this age group. Your pediatrician may recommend alternative antibiotics for very young infants.