• Cefdinir and amoxicillin are antibiotics used to treat bacterial infections.
• The drugs are in different classes. Cefdinir is a cephalosporin antibiotic and amoxicillin is a penicillin-type antibiotic.
• Cefdinir is only available as a generic. The Omnicef brand has been discontinued and there are no other brand names available for cefdinir available in the U.S. Brand names for amoxicillin include Amoxil, Moxatag, and Larotid.
• Side effects of cefdinir and amoxicillin that are similar include diarrhea, nausea, abdominal pain, vomiting, and rash.
• Side effects of cefdinir that are different from amoxicillin include vaginal yeast infection, vaginitis, and headache.
• Side effects of amoxicillin that are different from cefdinir include dizziness, heartburn, insomnia, itching, confusion, easy bruising, bleeding, and allergic reactions.

Amoxicillin belongs to a class of antibiotics called penicillins. Other members of this class include ampicillin (Unasyn), piperacillin (Pipracil), and ticarcillin (Ticar). These antibiotics all have a similar mechanism of action. They do not directly kill bacteria, but they stop bacteria from multiplying by preventing bacteria from forming the walls that surround them. The walls are necessary to protect bacteria from their environment and to keep the contents of the bacterial cell together. Bacteria cannot survive without a cell wall. Amoxicillin is effective against many different bacteria including H. influenzae, N. gonorrhoea, E. coli, Pneumococci, Streptococci, and certain strains of Staphylococci.

Cefdinir

Cefdinir generally is well tolerated. The most common side effects are:

• Diarrhea or loose stools
• Nausea
• Abdominal pain
• Vaginal moniliasis
• Vaginitis
• Vomiting
• Rash
• Headache

Rare side effects include:

• Abnormal liver tests
• Allergic reactions
• Abnormal stool
• Constipation
• Dry mouth

Cefdinir may cause false test results with some tests for sugar in the urine.
Like most antibiotics, cefdinir may cause a condition called pseudomembranous colitis (Clostridium difficile colitis), a potentially serious bacterial infection of the colon.

Patients who develop signs of pseudomembranous colitis after starting cefdinir (diarrhea, fever, abdominal pain, and possibly shock) should contact their doctor immediately.

Persons who are allergic to the penicillin class of antibiotics, for example, amoxicillin, amoxicillin and clavulanic acid (Augmentin), which are related to cephalosporins, may or may not be allergic to cephalosporins.

Amoxicillin

Side effects due to amoxicillin include:

• diarrhea,
• dizziness,
• heartburn,
• insomnia,
• nausea,
• itching,
• vomiting,
• confusion,
• abdominal pain,
• easy bruising,
• bleeding,
• rash, and
• allergic reactions.

People who are allergic to the cephalosporin class of antibiotics, which are related to the penicillins, for example, cefaclor (Ceclor), cephalexin (Keflex), and cefprozil (Cefzil), may or may not be allergic to penicillins.
Serious but rare reactions include:

• seizures,
• severe allergic reactions (anaphylaxis), and
• low platelet (thrombocytopenia) or red blood cell count.

Amoxicillin can alter the normal bacteria in the colon and encourage overgrowth of some bacteria such as Clostridium difficile which causes inflammation of the colon (pseudomembranous colitis). Patients who develop signs of pseudomembranous colitis after starting amoxicillin (diarrhea, fever, abdominal pain, and possibly shock) should contact their physician immediately.

Cefdinir

• 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.

Amoxicillin

• For most infections in adults the dose of amoxicillin is 250 mg every 8 hours, 500 mg every 8 hours, 500 mg every 12 hours or 875 mg every 12 hours, depending on the type and severity of infection.
• For the treatment of adults with gonorrhea, the dose is 3 g given as one dose.
• For most infections, children older than 3 months but less than 40 kg are treated with 25 or 45 mg/kg/day in divided doses every 12 hours or 20 or 40 mg/kg/day with one-third of the daily dose given every 8 hours depending on the type and severity of the infection.
• Amoxicillin can be taken with or without food.

Cefdinir

• 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.

Amoxicillin

Amoxicillin is rarely associated with important drug interactions.

Cefdinir

• 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.

Amoxicillin

• Penicillins are generally considered safe for use by pregnant women who are not allergic to penicillin.
• Small amounts of amoxicillin may be excreted in breast milk and may cause diarrhea or allergic responses in nursing infants. Amoxicillin is generally considered safe to use while breastfeeding. Amoxicillin is used to treat infections in the newborn.