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Cefdinir vs. Keflex: Antibiotic Uses & Side Effects

What is the difference between cefdinir and Keflex?

What are cefdinir and Keflex?

Cefdinir and Keflex (cephalexin) are cephalosporin antibiotics used to treat infections caused by susceptible bacteria such as infections of the tonsils (tonsillitis), throat (strep throat), middle ear (otitis media), larynx (laryngitis), bronchi (bronchitis), lungs (pneumonia), sinuses (sinusitis), and skin and other soft tissues. Other cephalosporin antibiotics include cefuroxime (Zinacef), cefpodoxime (Vantin), cefaclor (Ceclor), cefixime (Suprax), and cefprozil (Cefzil).

What are the side effects of cefdinir and Keflex?



The most common side effects of cephalexin are:

Individuals who are allergic to penicillin may also be allergic to cephalexin. Serious but rare reactions include seizures, severe allergic reactions (anaphylaxis), and low platelet or red blood cell count.

Cephalexin, like almost all antibiotics, may cause mild or severe cases of pseudomembranous colitis, a mild to severe inflammation of the colon. Antibiotics, including cephalexin alter the types of bacteria in the colon and permit overgrowth of a bacterium called Clostridium difficile. Studies indicate that toxins produced by Clostridium difficile are a primary cause of pseudomembranous colitis.

What is the dosage of cefdinir vs. Keflex?


  • Cefdinir is taken once or twice daily, depending on the type and severity of the infection.
  • The capsules or suspension can be taken with or without food.
  • Patients with advanced kidney disease may need to take lower doses to prevent accumulation of cefdinir since it is eliminated from the body by the kidneys.
  • For adult infections the usual dose is 300 mg every 12 hours or 600 mg per day for 5-10 days depending on the nature and severity of the infection.
  • The recommended dose for children 6 months to 12 years of age is 7 mg/kg every 12 hours or 14 mg/kg per day for 5-10 days depending on the type of infection.
  • For most infections, once daily dosing is as effective as twice daily dosing, although once daily dosing has not been evaluated for the treatment of skin infections or pneumonia.


  • The dose of cephalexin for adults is 1 to 4 grams in divided doses.
  • The usual adult dose is 250 mg every 6 hours.
  • Some infections may be treated with 500 mg every 12 hours.
  • Children are treated with 25-100 mg/kg/day in divided doses.
  • The dosing interval may be every 6 or 12 hours depending on the type and seriousness of the infection.


Bowel regularity means a bowel movement every day.
See Answer

What drugs interact with cefdinir vs. Keflex?


  • Aluminum or magnesium containing antacids reduce the absorption of cefdinir from the intestine. Separating the administration of cefdinir and such antacids by two hours prevents this interaction.
  • Iron supplements also reduce the absorption of cefdinir. Separating the administration of cefdinir and iron supplements by two hours prevents this interaction. There have been reports of reddish stool in patients who have received cefdinir. This could be due to the formation of a chemical complex between cefdinir and iron in the stomach.


  • Cephalexin may reduce the effect of BCG and typhoid vaccines. Cephalexin should not be combined with BCG or typhoid vaccine unless there are no other options.

Are cefdinir and Keflex safe to take while pregnant or breasfeeding?


There are no adequate studies of cefdinir in pregnant women; however, studies in animals suggest no important effects on the fetus.
Cefdinir is not secreted in human milk.


Cephalexin is excreted in breast milk. Cephalexin should be used with caution or stopped when breastfeeding.


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