Cefaclor vs Amoxicillin: Key Differences and When to Choose Each

When your doctor prescribes an antibiotic for a bacterial infection, you might hear Cefaclor, a second-generation cephalosporin antibiotic used for ear, lung, and skin infections or amoxicillin, a penicillin-class antibiotic commonly used for sinus, throat, and urinary tract infections. Both fight bacteria, but they’re not interchangeable. Choosing one over the other depends on your infection type, allergy history, and how your body responds to each drug.

Amoxicillin is one of the most prescribed antibiotics in the world because it’s broad-spectrum, well-tolerated, and cheap. It works well for common bugs like Streptococcus pneumoniae and Haemophilus influenzae — the usual suspects in ear infections and bronchitis. But if you’re allergic to penicillin, amoxicillin is off the table. That’s where Cefaclor, a cephalosporin antibiotic that’s structurally different from penicillin but still targets similar bacteria comes in. It’s often used as an alternative when penicillin isn’t safe, and it’s especially useful for recurrent ear infections or when amoxicillin hasn’t cleared up the infection. While both drugs can cause stomach upset or diarrhea, Cefaclor has a slightly higher chance of triggering a rash in kids, especially if they’ve had mononucleosis.

Another key difference? Resistance. Over time, some bacteria have learned to resist amoxicillin — especially in areas where it’s been overused. Cefaclor can sometimes work when amoxicillin doesn’t, because it’s more stable against certain bacterial enzymes that break down penicillin. But it’s not a magic bullet. If you’ve had multiple courses of antibiotics recently, neither might work well. That’s why doctors don’t just pick one at random — they look at your symptoms, your history, and sometimes even lab results.

You’ll find real-world comparisons in posts like Tinidazole vs Alternatives and Metformin vs Alternatives — both show how patients and providers weigh effectiveness, side effects, and cost when choosing between similar drugs. The same logic applies here. If you’ve been on amoxicillin before and it didn’t help, Cefaclor might be next. If you’ve had a rash after penicillin, Cefaclor is often tried first. But if you’re treating a simple strep throat and have no allergies, amoxicillin is still the go-to.

There’s no single "better" drug here. It’s about matching the right tool to the job. The posts below give you the details you need to understand why one might be chosen over the other — from dosing schedules and side effects to what infections each handles best. You won’t find marketing fluff or vague advice. Just clear, practical comparisons based on real prescribing patterns and patient outcomes.