Cefaclor Dosage: What You Need to Know About Dosing, Uses, and Safety

When you're prescribed Cefaclor, a second-generation cephalosporin antibiotic used to treat bacterial infections like ear infections, sinusitis, and pneumonia. Also known as Cefaclor monohydrate, it works by stopping bacteria from building cell walls, making it effective against many common infections. Unlike some antibiotics, Cefaclor is often chosen for kids because it comes in liquid form and has a milder taste than alternatives like amoxicillin.

Getting the Cefaclor dosage right matters—too little won’t clear the infection, too much raises your risk of side effects like diarrhea, nausea, or rash. For adults, the typical dose is 250 mg every 8 hours, or 500 mg every 12 hours, depending on how serious the infection is. Kids get doses based on weight: usually 20 mg per kg of body weight per day, split into three doses. If your child has kidney issues, the doctor might lower the dose. Never skip doses or stop early, even if you feel better—this is how resistant bacteria start.

Cefaclor is part of the cephalosporin antibiotics, a class of beta-lactam drugs that includes cephalexin and cefdinir, which are often used when someone is allergic to penicillin—but not always. About 10% of people with penicillin allergies also react to cephalosporins, so tell your doctor your full allergy history. It’s also not the first choice for every infection. For example, if you have strep throat, amoxicillin is usually preferred. But for ear infections that don’t respond to amoxicillin, Cefaclor is a solid next step.

Many people wonder how Cefaclor compares to other antibiotics like Cephalexin, a first-generation cephalosporin often used for skin infections and urinary tract infections. Cephalexin is cheaper and works well for simpler cases, but Cefaclor covers a broader range of bacteria, especially those causing respiratory infections. That’s why doctors sometimes pick Cefaclor when a cold turns into a sinus infection or bronchitis.

Don’t take Cefaclor with antacids or iron supplements—they can block absorption. Take it on an empty stomach, or at least 1 hour before or 2 hours after eating. Alcohol doesn’t interact directly, but it can make nausea worse. If you’re on birth control, Cefaclor might reduce its effectiveness, so use a backup method during treatment and for a week after.

What you’ll find below are real, practical guides from people who’ve used Cefaclor—or needed to choose between it and other antibiotics. You’ll see how dosage changes for kids, what side effects to watch for, how long it takes to work, and when to call your doctor. There’s also direct comparisons with other drugs like Cephalexin and amoxicillin, so you know exactly what you’re getting into before you start the prescription.