Along with its needed effects, cefprozil may cause some unwanted or undesirable effects. Generally, cefprozil is well tolerated and many people will not experience unwanted effects. The frequency and severity of these effects is dependant on many factors including dose, duration of therapy and individual susceptibility. Possible unwanted effects include:

• diarrhea
• nausea
• vomiting

Uncommon:

• stomach ache
• itching in genital and vaginal area
• allergic reaction (hives, itching, rash, difficulty breathing)

Rare:

• headache
• nervousness
• hyperactivity
• dizziness

Cefprozil is an antibiotic medication that kills various bacteria. It works by inhibiting the synthesis of one of the building blocks needed for the bacteria to make it's cell wall. This results in a cell wall that is defective and more likely to rupture. The effectiveness of cefprozil depends on factors such as dose, concentration in the blood as well as other body fluids and tissue, and the susceptibility of the bacteria. Cefprozil does not kill all types of bacteria, but only those that have a sensitivity to this antibiotic. Infections caused by bacteria that are not sensitive to cefprozil will not show improvement after taking this medication.

Taking the antibiotic repeatedly or for prolonged periods may result in bacterial or fungal overgrowth which can lead to a second infection. When this occurs, the cefprozil may need to be stopped and another antibiotic prescribed to treat the new infection.
Diarrhea often develops while taking cefprozil. This is sometimes caused by an overgrowth of bacteria in the gut that are not killed by the antibiotic. In severe cases, this may be life threatening and would require treatment with other antibiotics. In mild cases, symptoms disappear shortly after the drug is discontinued.
There is evidence to show that people who are allergic to penicillin may also be allergic to cefprozil and vice versa. Be sure to inform your doctor and pharmacist of any antibiotic allergy or suspected allergy that you may have had in the past.

Drug Interactions: It is important to tell your doctor and pharmacist of any prescription or over-the-counter medications you are taking. Interactions have been known to occur between cefprozil and probenecid (e.g. Benemid®). Use is not recommended in the following situations:

• allergy to cephalosporins (e.g. cephalexin)

False positive direct Coombs' tests (test used in detecting a type of blood disorder) may be caused by cefprozil.Cefprozil may cause false urine test results for glucose.

Caution is recommended in the following situations:

• kidney disease
• allergy to penicillin
• stomach or intestinal disease (e.g. colitis)
• prolonged, repeated therapy

Use in pregnancy: Can be used in pregnancy if necessary, however, other medications is this family are preferred.  Consult your doctor or pharmacist if you suspect you are pregnant.
Use while breastfeeding: Cefprozil does appear in breast-milk, but in small amounts.  Generally considered safe for use in breastfeeding. Consult your doctor or pharmacist before use.