Cefdinir
Beta-lactams
Beta-lactams
Oral third-generation cephalosporin for otitis, pharyngitis, sinusitis and mild pneumonia; with iron it can turn the stools red.
Quick facts
- Group
- Beta-lactams
- Target
- Penicillin-binding proteins (bacterial transpeptidases)
- Used for
- Acute otitis media in children
- Key effects
- Diarrhoea · Vaginal candidiasis and vaginitis · Nausea
- Monitor
- Diarrhoea during and after treatment · Stool colour
- ATC
- J01DD15
No doses: the clinician sets them by the current guideline.
Mechanism of action
No structure of cefdinir bound to a PBP is published; the figure shows cefixime, another oral third-generation cephalosporin with a vinyl group in the same position, acylating Neisseria gonorrhoeae PBP2.
Cefdinir acylates the penicillin-binding proteins and blocks peptidoglycan cross-linking, so it is bactericidal. It is stable against some, but not all, beta-lactamases and is used mainly against pneumococci, S. pyogenes, H. influenzae and Moraxella in outpatient respiratory infections.
- Absorbed by mouth (low bioavailability)
- Acylates the PBPs of the bacterial wall
- Peptidoglycan cross-linking stops
- The bacterium lyses (bactericidal)
Indications
- Acute otitis media in children Acute otitis media →
- Pharyngitis and tonsillitis Streptococcal pharyngitis →
- Mild community-acquired pneumonia and flares of chronic bronchitis Community-acquired pneumonia →
- Acute maxillary sinusitis Acute rhinosinusitis →
- Uncomplicated skin infections
Adverse effects
Common
- Diarrhoea (the most common)
- Vaginal candidiasis and vaginitis
- Nausea, abdominal pain and headache
- Reddish stools when combined with iron
Contraindications
- Allergy to cephalosporins
Key interactions
- Aluminium or magnesium antacids
- Reduce absorption; doses are separated by at least 2 hours.
- Iron supplements and multivitamins with iron
- Reduce absorption (separated by at least 2 hours) and form a complex that turns stools red.
- Probenecid
- Reduces renal excretion and raises cefdinir levels.
What is monitored
- Diarrhoea during and after treatment
- Stool colour: reddish from iron is harmless; blood or black stools are not
Administration and safety
- Oral, as capsules or suspension
- Separate from antacids and iron supplements
- The suspension contains sucrose, worth knowing in people with diabetes
Pregnancy and breastfeeding
Animal studies showed no harm and there are no adequate studies in pregnant women; it is used only when clearly needed.
Nursing care
- Ask about penicillin and cephalosporin allergy
- Explain to carers that reddish stools from iron are not blood, and when to seek care
- Review the iron supplements and antacids the person uses
- Teach to finish the course
Pharmacokinetics
- Absorption
- Oral, with low bioavailability (around 25% for the suspension); aluminium or magnesium antacids and iron reduce it.
- Metabolism
- Hardly metabolised.
- Elimination
- Mainly renal.
- Half-life
- Short, about 1.7 hours.
Test yourself
Think of the answer, then tap the question to see it.
A child on cefdinir and an iron supplement has reddish stools. What is the most likely cause?
A non-absorbable complex of cefdinir and iron in the gut; it is harmless, though bleeding is ruled out if there are other signs.
Which over-the-counter products reduce cefdinir absorption?
Aluminium or magnesium antacids and iron supplements or multivitamins; they are separated by at least 2 hours.
Which generation does cefdinir belong to?
The third generation of oral cephalosporins.
Connections
← Back to the class: Beta-lactams
Educational content on how drugs work; not a prescribing guide and no substitute for a health professional's advice. No doses are given.
Sources: DailyMed - CEFDINIR capsule (DailyMed (U.S. National Library of Medicine), 2026); Cefdinir: MedlinePlus Drug Information (MedlinePlus (U.S. National Library of Medicine), 2026); Crystal structure of transpeptidase domain of PBP2 from Neisseria gonorrhoeae acylated by cefixime (RCSB Protein Data Bank, 2026).
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Representative model, for educational purposes only.