Cefprozil Side Effects: What's Normal and What's Not

Cefprozil (formerly sold as brand-name Cefzil) is a second-generation cephalosporin antibiotic prescribed for infections like strep throat, ear infections, sinusitis, bronchitis, and skin infections. Like all antibiotics, it can cause side effects — most of which are mild and go away on their own.

But some side effects are serious and need immediate medical attention. This guide breaks down exactly what to expect, what's concerning, and when to call your doctor.

What Is Cefprozil?

Cefprozil is a prescription oral antibiotic available as 250 mg and 500 mg tablets and as an oral suspension (liquid) for children. It works by disrupting bacterial cell wall synthesis, killing the bacteria causing your infection. For a full overview of how it works, see our guide on Cefprozil's mechanism of action.

Most people tolerate Cefprozil well. In clinical trials, side effects were generally mild and affected a small percentage of patients.

Common Side Effects

These side effects occur in a noticeable number of patients and are usually not dangerous. They often improve as your body adjusts to the medication:

• Nausea — the most frequently reported side effect; taking Cefprozil with food may help
• Diarrhea — common with most antibiotics; usually mild
• Vomiting — more common in children taking the suspension
• Stomach pain or abdominal discomfort
• Dizziness — usually mild; avoid driving if affected
• Genital itching or vaginal yeast infection — antibiotics can disrupt normal flora
• Diaper rash — seen in infants taking the liquid form
• Unpleasant taste — particularly with the oral suspension

These side effects typically resolve within a day or two of finishing your course. If they persist or become bothersome, talk to your doctor — but don't stop taking the antibiotic early without medical advice.

Serious Side Effects: When to Call Your Doctor Immediately

While rare, some Cefprozil side effects require urgent medical attention. Call your doctor or go to the emergency room if you experience:

• Signs of a severe allergic reaction (anaphylaxis) — rash, hives, swelling of the face/tongue/throat, difficulty breathing, or a feeling of tightness in the chest. This is a medical emergency.
• Watery or bloody diarrhea — this may indicate Clostridioides difficile-associated diarrhea (CDAD or "C. diff"), a potentially serious gut infection. It can occur during treatment or even weeks after finishing the antibiotic.
• Seizures — rare, but more likely in patients with kidney impairment or those taking very high doses.
• Severe skin reactions — including widespread rash, blistering, peeling skin, or mouth sores. Stevens-Johnson syndrome is extremely rare but serious.

Important: If you have a known allergy to penicillin, tell your doctor before taking Cefprozil. There is a small (1–2%) cross-reactivity risk between penicillins and cephalosporins.

Side Effects in Specific Populations

Children

Cefprozil is FDA-approved for children 6 months and older. The most common side effects in kids are diarrhea, diaper rash (infants), vomiting, and stomach pain. The oral suspension contains aspartame, so it should be used with caution in children with phenylketonuria (PKU).

Pregnant and Breastfeeding Women

Cefprozil is classified as Pregnancy Category B, meaning animal studies have not shown fetal risk, but there are no well-controlled studies in pregnant women. It should be used only if clearly needed. Cefprozil is excreted in small amounts in breast milk — discuss with your doctor if you're breastfeeding.

Patients With Kidney Problems

If your creatinine clearance is below 30 mL/min, your doctor should adjust your dose. Cefprozil is cleared through the kidneys, and impaired kidney function can lead to higher drug levels and an increased risk of side effects like seizures.

How to Manage Common Side Effects

Here are practical tips to reduce discomfort while taking Cefprozil:

• For nausea and stomach pain: Take with food or a small snack. Avoid taking on a completely empty stomach.
• For diarrhea: Stay hydrated. Eat bland foods (bananas, rice, toast). Probiotics may help restore gut bacteria, but take them a few hours apart from your antibiotic dose.
• For yeast infections: Over-the-counter antifungal treatments (like Monistat) are usually effective. Ask your pharmacist.
• For diaper rash in infants: Change diapers frequently and use a barrier cream like zinc oxide.
• For dizziness: Avoid driving or operating heavy machinery until you know how Cefprozil affects you.

If any side effect is severe or doesn't improve, contact your healthcare provider. They may adjust your dose or switch you to a different antibiotic.

Final Thoughts

Cefprozil is generally well-tolerated, and most people experience only mild side effects like nausea or diarrhea. Serious reactions — like anaphylaxis, C. diff, or severe skin reactions — are rare but important to watch for.

The most important thing you can do is finish your full course of treatment as prescribed, even if you feel better. Stopping early can lead to antibiotic resistance and recurring infections.

If you're having trouble finding Cefprozil at your pharmacy, check Medfinder to see which pharmacies near you have it in stock.