Cefaclor Monohydrate: What It Is, How It Works, and What You Need to Know

When you’re prescribed an antibiotic for a stubborn ear infection, sinusitis, or bronchitis, you might see Cefaclor monohydrate, a second-generation cephalosporin antibiotic used to treat bacterial infections. Also known as Cefaclor, it’s one of the more commonly prescribed oral antibiotics for kids and adults alike. It’s not flashy, but it’s reliable—especially for infections that don’t respond to basic penicillins. Unlike some broad-spectrum drugs, Cefaclor monohydrate targets specific bacteria without wiping out your gut flora as hard as others might.

It’s part of the cephalosporin class of antibiotics that work by stopping bacteria from building strong cell walls, which makes them burst and die. This is the same mechanism as cefalexin or cefdinir, but Cefaclor monohydrate has a slight edge in penetrating lung tissue and middle ear fluid, which is why doctors often reach for it when treating pneumonia or ear infections in children. It’s not for every infection, though. If you’ve had a severe allergic reaction to penicillin, you might still react to Cefaclor—about 5-10% of people do. That’s why your doctor checks your history before prescribing it.

What makes Cefaclor monohydrate different from other antibiotics isn’t just how it kills bacteria—it’s how it’s formulated. The "monohydrate" part means it’s combined with one water molecule to improve stability and absorption. That’s why you’ll see it listed as Cefaclor monohydrate on prescriptions, not just Cefaclor. It’s the same drug, but the extra water helps it dissolve better in your gut, so you get more of the active ingredient where it needs to go.

You’ll find it used for respiratory infections, skin infections like cellulitis, and sometimes urinary tract infections if other options aren’t working. It’s not first-line for strep throat anymore—amoxicillin usually is—but when that fails or you’re allergic to it, Cefaclor steps in. It’s also cheaper than newer antibiotics, which is why it’s still in use in clinics and hospitals around the world.

Side effects? Mild for most people—stomach upset, diarrhea, or a rash. But if you get severe diarrhea with blood or fever, stop taking it and call your doctor. That could be C. diff, a dangerous infection that can follow antibiotic use. And don’t skip doses. Even if you feel better in two days, finish the full course. Stopping early doesn’t just make you sick again—it helps create drug-resistant bacteria.

There’s no magic here. Cefaclor monohydrate isn’t a wonder drug. But it’s been around since the 1980s for a reason: it works when it’s supposed to. And in a world where antibiotics are getting harder to find, knowing when and how this one fits into your treatment plan matters.

Below, you’ll find real patient guides on tracking recalls, comparing antibiotics like Tinidazole and Metronidazole, and understanding how to use prescriptions safely. These aren’t just lists—they’re practical tools to help you stay informed, avoid scams, and make smarter choices with your health.