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What is Cloxacillin?

Thomma Grindstaff
Thomma Grindstaff

Cloxacillin is an semisynthetic antibiotic in the same class of medications as penicillin. It's primarily used to treat infections caused by Staphylococcus, Streptococcus, and pneumococcus or Streptococcus pneumoniae bacteria. Cloxacillin is often prescribed by medical professionals and is effective in treating a wide variety of conditions, including skin and ear infection, staph infection, strep throat, sinusitis, and pneumonia. The medication is also used to treat sexually transmitted diseases (STDs) such as syphilis and gonorrhea.

Available through a doctor's prescription, this drug must be taken as directed in order to be effective. A patient should take the medication one to two hours before meals, along with a full glass of water. Sodas or other carbonated drinks shouldn't be consumed along with the antibiotic because they could lessen its effect. Doses should be taken at regular intervals so that the amount of medicine in the body remains as high as possible. A patient must take the full amount of medicine prescribed, even if he or she starts feeling better beforehand.

Cloxacillin may be used to treat ear infections.
Cloxacillin may be used to treat ear infections.

Capsules must not be crushed but must be swallowed whole. Patients who miss a dose should take it as soon as they remember, but they must not take a double dose. While being treated, patients should avoid alcohol since it can cause stomach upset in conjunction with the drug.

The antibiotic destroys the cell walls of bacteria, thereby killing them. Some strains of bacteria, however, have developed resistance to cloxacillin and other penicillin antibiotics. These bacteria are often called super bugs.

Doctors may prescribe cloxacillin to treat strep throat.
Doctors may prescribe cloxacillin to treat strep throat.

People who are allergic to penicillin or cephalosporin antibiotics shouldn't take cloxacillin. The medication should also be avoided by people who have cystic fibrosis. Women who are taking oral contraceptives to prevent pregnancy should switch to another birth control method while being treated with this drug.

Cloxacillin may cause side effects, which include dizziness, loss of appetite, and nausea. Patients who experience more serious side effects should stop taking the medication. These side effects include hives, convulsions, fever, rash, sores on the genitals, and swollen lymph nodes.

Cloxacillin may be used to treat pneumonia.
Cloxacillin may be used to treat pneumonia.

People with certain medical conditions should talk to their doctors before taking this drug for infections. These conditions include asthma and hay fever. Likewise, people who have a history of diabetes, colitis, liver disease, or kidney disease may not want to use this medicine.

The antibiotic is considered safe for use, under the supervision of a medical professional, by women who are pregnant. Mothers who breastfeed, however, should bottle feed their babies while being treated with cloxacillin. The drug has been shown to cause diarrhea in infants.

Discussion Comments


My six month old (7kg) baby has been prescribed to take 4ml of Cloxacillin. He had an insect bite mark on his body, which developed into an allergy reaction. I've started my child with this dose, but I am still very worried. Please advise me if this is safe. My pediatrician says its safe, and mild.


I am talking a medication with Cloaxcillin in it. I do feel dizziness and that my head is heavy. It's like I'm sleeping while my eyes are open. I hope I feel better soon and I hope all the sick people in the world have better health and be cured. I wish the best to everyone.


I’ve heard that cloxacillin sodium can beat the bacteria that has become tolerant of regular old penicillin. My doctor gave it to me, and I believe that it must have been stronger than penicillin, because it really floored my digestive system.

I had taken penicillin before with no problems. Cloxacillin gave me bad diarrhea and terrible abdominal cramps, though. After two days of this, I had to ask my doctor to give me something else, because I feared that I might become dehydrated. I could not go to work because of the pain in my stomach and intestines.


Sometimes cloxacillin could use a little help. When I had strep throat, the infection was so bad that my doctor gave me a steroid shot and a dose pack of steroid pills in addition to cloxacillin.

The antibiotic would fight the strep bacteria, and the steroids would make my immune system stronger in order to help the antibiotics do their job. Also, the steroids made me feel strong and vital and so much better after just one day, and antibiotics alone could not have accomplished that.

Doctors refrain from giving out steroids for every little sinus infection, though. They have some undesirable side effects, so if cloxacillin alone can get the job done, they will only prescribe it.


@seag47 - You know those super bugs that the article mentions? They were created by people who didn’t take all of their antibiotics.

When you don’t take the full dosage for the prescribed amount of time, then the bacteria has a chance to regroup. It can come back on you stronger than before, and you will be unable to fight it off with cloxacillin, because it became tolerant of it.

Many people make the mistake of stopping their antibiotics before it is time. This makes bacteria harder to fight. If everyone would just take the full course of antibiotics, then we wouldn’t have super bugs, and we could all get well faster.


I have often wondered why it is so important to take all of the cloxacillin dosage. If I am already feeling better, then I want to stop taking it.

Cloxacillin just makes food unappealing to me while I’m on it. Everything tastes weird, and my stomach is sensitive.

I really enjoy eating, so I want to get off this medication as soon as I feel healed. Why do I have to take fourteen days worth of it when I feel all better after five? It just seems like a waste, because the medicine itself makes me feel bad.


I am sensitive to a lot of medications, and have not been able to take Cloxacillin. I was originally prescribed this for a sinus infection that I seem to get every fall.

The Cloxacillin dose was not that large, but I immediately noticed some side effects. I became dizzy and nauseated and knew I was having some kind of reaction to the medication.

My doctor told me to stop taking it and prescribed a different antibiotic for me. I was thankful that I realized I was allergic to this very quickly. I am also glad there were other alternative antibiotics to take.

A sinus infection is miserable not matter what, but not being able to take an antibiotic to clear it up would really be miserable.


My kids have had a lot of ear infections, and Cloxacillin is one antibiotic that all of them have taken at one point. None of my kids are allergic to penicillin so they have never had any problems with the antibiotics.

If they have to take them on a frequent basis, the doctor closely watches to make sure they don't build up a resistance to it. If you take one antibiotic too often, your body will stop responding to it.

I also have to make sure my kids finish all of the pills. They usually start feeling so much better in a few days and it is tempting to quit giving them the medication.

I know people who have stopped taking them after a few days, and it seems like the infection always comes back. Sometimes it is worse the second time around than it was the first time.


I know that every person responds differently to prescribed antibiotics. One of my friends is allergic to penicillin and has had trouble with almost every kind of antibiotic she has ever tried to take.

This really puts her at a disadvantage because so many common infections are treated with antibiotics. She has only found one antibiotic that she can take without having an allergic reaction, and I am not sure what the name of that one is.

My grandpa had a severe reaction to the Amoxicillin antibiotic. He was taking this for pneumonia and never recovered from the reaction. My dad also had a strange reaction to this antibiotic, so this is one I try to avoid if at all possible.

Usually there are many other options that doctors have to choose from that will help clear up the infection.


I have taken several antibiotics during my life and this is the first time I heard that carbonated drinks can lessen the effect of the medication.

This is good to know as I like to drink soda and usually have more than one during the day.

I am assuming this is probably true for all antibiotics, not just Cloxacillin. I was prescribed some Cloxacillin capsules to take when I had strep throat.

I have always been curious how a doctor determines which antibiotic is best for a person or particular condition. I have never had any trouble taking antibiotics and usually get really quick results.

When I go to the doctor with some type of infection that needs to be cleared up right away, taking antibiotics is the fastest way I know to take care of the problem.

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    • Cloxacillin may be used to treat ear infections.
      By: Lisa Eastman
      Cloxacillin may be used to treat ear infections.
    • Doctors may prescribe cloxacillin to treat strep throat.
      By: Alexander Raths
      Doctors may prescribe cloxacillin to treat strep throat.
    • Cloxacillin may be used to treat pneumonia.
      Cloxacillin may be used to treat pneumonia.
    • Sinusitis may be treated with cloxacillin.
      By: Minerva Studio
      Sinusitis may be treated with cloxacillin.
    • Cloxacillin must be taken one to two hours before meals with a glass of water.
      Cloxacillin must be taken one to two hours before meals with a glass of water.
    • Side effects of cloxacillin may include nausea.
      By: kmiragaya
      Side effects of cloxacillin may include nausea.
    • Cloxacillin may be used to treat sexually transmitted diseases such as gonorrhea and syphilis.
      By: vgstudio
      Cloxacillin may be used to treat sexually transmitted diseases such as gonorrhea and syphilis.