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Overview: Cefaclor is used for certain bacterial infections. It works by killing the bacteria that cause the infection. Common side effects include rash and diarrhea. Serious side effects are much less common, but can include a type of diarrhea that is difficult to treat. Notify your healthcare provider right away if you develop watery diarrhea. Cefaclor comes as a capsule, extended-release tablet, and liquid that you take by mouth.

Uses

What is cefaclor used for?

Cefaclor is an antibiotic that is commonly taken for the following infections caused by certain bacteria (bacterial infection).

Cefaclor may not be appropriate for some of the infections listed above, depending on which germs are causing the infection. Bacteria in some locations may have developed resistance to cefaclor, which will make it not work as well.

Cefaclor may also be used for other conditions as determined by your healthcare provider.

How does cefaclor work (mechanism of action)?

Cefaclor kills certain bacteria by preventing them from being able to create their cell wall.

How is cefaclor supplied (dosage forms)?

Dosage forms and strengths

  • 250 mg, 500 mg oral capsules
  • 500 mg oral extended-release tablets
  • 125 mg/5 mL, 187 mg/5 mL, 250 mg/5 mL, 375 mg/5 mL oral suspension

How should I store cefaclor?

Oral Capsules and Extended-Release Tablets. Cefaclor capsules and extended release tablets should be stored at room temperature, between 68 F to 77 F (20 C to 25 C). It can be exposed to temperatures between 59 F to 86 F (15 C to 30 C) for shorter periods of time, such as when transporting it. Store in a cool, dry place. 

Oral Liquid. Cefaclor liquid should be stored with a tightly closed lid, in the refrigerator, between 36 F and 46 F (2 C and 8 C). Throw any unused cefaclor liquid away after 14 days. 

Side Effects

What are the most common side effects of cefaclor?

The most common side effects of cefaclor are listed below. Tell your healthcare provider if you have any of these side effects that bother you.

  • Rash
  • Diarrhea

There may be other side effects of cefaclor that are not listed here. Contact your healthcare provider if you think you are having a side effect of a medicine. In the U.S., you can report side effects to the FDA at www.fda.gov/medwatch or by calling 800-FDA-1088. In Canada, you can report side effects to Health Canada at www.health.gc.ca/medeffect or by calling 866-234-2345.

What are the serious side effects of cefaclor?

While less common, the most serious side effects of cefaclor are described below, along with what to do if they happen.

Severe Allergic Reactions. Cefaclor may cause allergic reactions, which can be serious. Stop taking cefaclor and get help right away if you have any of the following symptoms of a serious allergic reaction.

  • Breathing problems or wheezing
  • Racing heart
  • Fever or general ill feeling
  • Swollen lymph nodes
  • Swelling of the face, lips, mouth, tongue, or throat
  • Trouble swallowing or throat tightness
  • Itching, skin rash, or pale red bumps on the skin called hives
  • Nausea or vomiting
  • Dizziness, feeling lightheaded, or fainting
  • Stomach cramps
  • Joint pain

Severe Skin Reactions. Cefaclor can cause severe skin reactions called Stevens-Johnson Syndrome (SJS) and Toxic Epidermal Necrolysis (TEN) that can lead to death if not treated. If you develop a rash, stop cefaclor and call your healthcare provider right away. Get emergency help right away if you have any of the following symptoms of SJS or TEN.

  • Painful red or purple skin that looks burned and peels off
  • Flat red rash or blisters on your skin, mouth, nose, and genitals
  • Red, painful, watery eyes

Seizures. Some people who have taken cefaclor have reported having seizures. There are many different types of seizures and some of them are not easy to recognize. Stop taking cefaclor and call your healthcare provider if you experience any of the following signs that a seizure is happening or could happen.

  • Muscle twitching, jerking, spasms, tremors, or other uncontrolled movements
  • Stiffening of your arms and legs
  • Feeling anxious, nervous, confused, or a sense of dread
  • Feeling dizzy or lightheaded
  • Falling or losing consciousness

Antibiotic-associated Diarrhea. An overgrowth of germs called Clostridioides difficile, or “C. diff,” can happen in your gut with many types of antibiotics, including cefaclor. This can cause a condition known as antibiotic-associated diarrhea and can happen even up to two months after stopping the antibiotic. Call your healthcare provider right away if you have any of the following symptoms of this condition.

  • Watery diarrhea
  • Diarrhea that does not go away
  • Blood in your stool (poop)
  • Severe stomach cramps
  • Fever that starts after you start or finish the medicine

Liver Damage. Liver damage, also called hepatotoxicity, can happen when taking cefaclor. Call your healthcare provider right away if you have any of the following symptoms of liver damage.

  • Nausea or vomiting
  • Stomach or belly pain
  • Fever
  • Weakness or unusual tiredness
  • Itching
  • Loss of appetite
  • Light-colored poop
  • Dark-colored urine
  • Your skin or the whites of your eyes turning yellowish in color (also called jaundice)

Blood Disorders. Cefaclor can cause blood disorders, such as agranulocytosis, aplastic anemia, hemolytic anemia, low platelet levels (thrombocytopenia), and low white blood cell levels (leukopenia or neutropenia). Stop taking cefaclor and get help right away if you have any of the following symptoms of blood disorders.

  • Fever, chills, or sweats
  • Sore throat
  • Cough or shortness of breath
  • Pale or yellowish skin
  • Easy bruising or bleeding
  • Frequent infection
  • Unusual weakness or tiredness
  • Dizziness, lightheadedness, or feeling like you are about to pass out
  • Headache
  • Fast or abnormal heartbeat
  • Mouth or throat sores
  • Swollen lymph nodes

Kidney Damage. Kidney damage can happen when taking cefaclor. Call your healthcare provider right away if you have any of the following symptoms of kidney damage.

  • Reduced need to pee
  • Swelling in your feet, ankles, or legs
  • Weakness or unusual tiredness
  • Difficulty catching your breath or chest pain/pressure
  • Confusion
  • Nausea
  • Seizures

Another Infection With Prolonged Use. Taking cefaclor for a long period of time may lead to an infection with other types of germs, such as fungi. Call your healthcare provider if your infection does not improve or gets worse.

Seizures. Some people who take cefaclor may have seizures. There are many different types of seizures and some of them are not easy to recognize. Stop taking cefaclor and call your healthcare provider if you have any of the following signs that a seizure is happening or could happen.

  • Muscle twitching, jerking, spasms, tremors, or other uncontrolled movements
  • Stiffening of your arms and legs
  • Feeling anxious, nervous, confused, or a sense of dread
  • Feeling dizzy or lightheaded
  • Falling or losing consciousness

Warnings & Precautions

Who should not use cefaclor?

Allergies to Ingredients. People who are allergic to any of the following should not take cefaclor.

  • Cefaclor
  • Any of the ingredients in the specific product dispensed

Your pharmacist can tell you all of the ingredients in the specific cefaclor products they stock.

What should I know about cefaclor before using it?

Do not take cefaclor unless it has been prescribed to you by a healthcare provider. Take it as prescribed.

Cefaclor only treats certain infections caused by bacteria. Cefaclor will not work for viral infections, such as the common cold, influenza, or coronavirus. It also will not work for any other non-bacterial infections. Taking cefaclor or any other antibiotic when it is not needed (infections other than those caused by bacteria, or the lack of an infection in general) may cause the antibiotic to not work for bacterial infections in the future.

Do not share cefaclor with other people, even if they have the same condition as you. It may harm them.

Keep cefaclor out of the reach of children. Since this cefaclor oral liquid should be kept in a refrigerator, take special precautions to keep it away from children who also use the refrigerator.

Do not chew, cut, or crush cefaclor extended-release tablets. They should be swallowed whole.

If taking cefaclor oral liquid, use an accurate measuring device to measure your dose. A household spoon is not an accurate measuring device and may cause you to take the wrong dose. Ask your pharmacist to recommend an appropriate measuring device. Shake cefaclor liquid well before measuring each dose.

What should I tell my healthcare provider before using cefaclor?

Tell your healthcare provider about all of your health conditions and any prescription or over-the-counter (OTC) medicines, vitamins/minerals, herbal products, and other supplements you are using. This will help them determine if cefaclor is right for you.

In particular, make sure that you discuss any of the following.

  • An allergy to penicillins and/or cephalosporins
  • Liver problems
  • Kidney problems
  • History of antibiotic-associated diarrhea
  • History of gastrointestinal problems

Other Medicines and Supplements. Cefaclor may interact with other medicines and supplements. Before taking cefaclor, tell your healthcare provider about any prescription or over-the-counter (OTC) medicines, vitamins/minerals, herbal products, and other supplements you are using. See the Interactions section for more details.

Pregnancy. It is not known if or how cefaclor could affect pregnancy or harm an unborn baby. Tell your healthcare provider if you are or plan to become pregnant.

Breastfeeding. Cefaclor passes into breast milk. Tell your healthcare provider if you are breastfeeding or plan to breastfeed. Your healthcare provider will advise you if you should take cefaclor while breastfeeding.

Interactions

Does cefaclor interact with foods or drinks?

There are no known interactions between cefaclor and foods or drinks.

It is unknown if drinking alcohol will affect cefaclor, but heavy drinking can slow your immune response and make it harder for your body to fight infection.

Does cefaclor interact with other medicines (drug interactions)?

Always tell your healthcare provider about any prescription or OTC medicines, vitamins/minerals, herbal products, and other supplements you are using.

In particular, make sure that you discuss if you are using any of the following before taking cefaclor.

  • An antacid containing calcium, aluminum, or magnesium
  • Probenecid, which is a medicine commonly used for gout
  • Warfarin, which is a blood thinner

This may not be a complete list of medicines that can interact with cefaclor. Always check with your healthcare provider.

Does interact with other drugs you are taking?

Enter your medication into the WebMD interaction checker

Overdose/Missed Dose

What should I do if I accidentally use too much cefaclor?

If you or someone else has used too much cefaclor, get medical help right away, call 911, or contact a Poison Control center at 800-222-1222.

What should I do if I miss a dose of cefaclor?

If you miss a dose, take it as soon as you remember. If it is almost time for your next dose, skip the missed dose and only take the next dose. Do not take double or extra doses.

It is important to complete your prescribed course of cefaclor, even if your symptoms get better or go away. This will reduce the risk that future infections are resistant to cefaclor or other similar medicines.