Updated: January 11, 2026

What Is Cefaclor XR? Uses, Dosage, and What You Need to Know in 2026

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Peter Daggett

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What Is Cefaclor XR?
What Is Cefaclor XR Used For?
Dosage and How to Take Cefaclor XR
Important Drug Interactions to Know
Who Should Not Take Cefaclor XR?
Pregnancy and Breastfeeding
How to Store Cefaclor XR

Cefaclor XR is a second-generation cephalosporin antibiotic used to treat bronchitis, sinusitis, and more. Get the complete overview of uses, dosage, and how to take it safely.

If you've been prescribed Cefaclor XR, you may be wondering exactly what it is, what it does, and how to take it correctly. This guide answers all the fundamentals so you can start your antibiotic course with confidence.

What Is Cefaclor XR?

Cefaclor XR (also known as cefaclor extended-release tablets) is a prescription antibiotic belonging to the second-generation cephalosporin class. The active ingredient is cefaclor, a semisynthetic beta-lactam antibiotic that has been used since its FDA approval in 1979. The XR (extended-release) formulation was developed to allow twice-daily dosing instead of the three-times-daily dosing required by immediate-release capsules.

Brand names have included Ceclor CD and Raniclor. The original brands have been discontinued, and only generic versions of cefaclor extended-release 500 mg tablets are currently available.

What Is Cefaclor XR Used For?

Cefaclor XR is FDA-approved to treat the following mild-to-moderate bacterial infections in adults and adolescents 16 years and older:

Acute bacterial exacerbations of chronic bronchitis (ABECB): Caused by Haemophilus influenzae, Moraxella catarrhalis, or Streptococcus pneumoniae

Secondary bacterial infections of acute bronchitis: Caused by the same organisms

Pharyngitis (strep throat) and tonsillitis: Caused by Streptococcus pyogenes (Group A strep)

Uncomplicated skin and skin-structure infections: Caused by Staphylococcus aureus or Streptococcus pyogenes

Importantly, cefaclor will NOT treat viral infections like the common cold, flu, or COVID-19. Using antibiotics for viral infections contributes to antibiotic resistance and will not help you recover faster.

Dosage and How to Take Cefaclor XR

Standard adult dose: 500 mg (one tablet) twice daily — every 12 hours

Maximum dose: 2,000 mg (2g) per day

Duration: 7 to 10 days, depending on the type and severity of infection

With food REQUIRED: Must be taken with food or within 1 hour of eating — without food, peak blood levels can drop by up to 67%, significantly reducing effectiveness

Swallow whole: Do not crush, chew, or break the extended-release tablet — doing so destroys the extended-release mechanism and may cause too much drug to be released at once

Important Drug Interactions to Know

Antacids (Mylanta, Maalox, Tums): Antacids containing aluminum or magnesium can reduce cefaclor absorption. Take antacids at least 1 hour before or 1 hour after Cefaclor XR.

Probenecid: Used for gout; can increase cefaclor blood levels by slowing kidney excretion. Tell your doctor if you take probenecid.

Warfarin: Cefaclor may enhance the anticoagulant effect of warfarin. Closer INR monitoring may be needed.

Who Should Not Take Cefaclor XR?

Patients with known hypersensitivity (allergy) to cephalosporin antibiotics

Patients under 16 years of age (ER formulation not established for children)

Patients with severe penicillin allergy (discuss with your doctor — cross-reactivity between penicillins and cephalosporins is possible but uncommon)

Patients with severely impaired renal function (dose adjustment required)

Pregnancy and Breastfeeding

Cefaclor is not expected to harm an unborn baby, but you should still inform your doctor if you are pregnant or planning to become pregnant. Cefaclor passes into breast milk in small amounts. While it is generally considered safe during breastfeeding, discuss the risks and benefits with your doctor or pharmacist.

How to Store Cefaclor XR

Store at room temperature (68-77°F / 20-25°C)

Keep in a tight, light-resistant container

Keep away from moisture and heat — do not store in the bathroom

Want to understand how cefaclor fights bacteria? Read How Does Cefaclor XR Work? Mechanism of Action Explained in Plain English for a patient-friendly deep dive.

Having trouble finding Cefaclor XR at your pharmacy? medfinder can call pharmacies near you to check which ones have it in stock.

Frequently Asked Questions

Cefaclor XR (extended-release) is formulated to release the drug slowly over time, allowing twice-daily dosing (500 mg every 12 hours). Regular (immediate-release) cefaclor capsules are dosed three times daily (250-500 mg every 8 hours). They are NOT interchangeable on a 1:1 basis — 500 mg XR BID is equivalent to 250 mg IR TID, not 500 mg IR BID.

Yes — this is critical. Cefaclor XR must be taken with food or within 1 hour of a meal. Without food, the peak blood level (Cmax) can drop by up to 67%, which significantly reduces the drug's effectiveness. This is different from immediate-release cefaclor capsules, which can be taken with or without food.

The typical course is 7-10 days, depending on the type and severity of infection. Always complete the full prescribed course even if you start feeling better earlier. Stopping an antibiotic early can allow surviving bacteria to rebound and potentially develop resistance.

Cefaclor XR is FDA-approved to treat acute bacterial exacerbations of chronic bronchitis, secondary bacterial infections of acute bronchitis, pharyngitis/tonsillitis (strep throat), and uncomplicated skin infections in patients 16 and older. It does NOT treat viral infections like the common cold or flu.

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