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Pronunciation: Klox a SiLL in

What is it

Cloxacillin is an antibiotic that belongs to the Penicillin class (penicillinase-resistant penicillin). It is a semi-synthetic antibiotic which is a chlorinated derivative of oxacillin.

Brand names with manufacturer

Cloxapen, Cloxacap, Tegopen and Orbenin


Prescription drug



The drug is used to treat different infections that are caused by penicillinase-producing staphylocococci. These organisms include group A beta-hemolytic streptococci, pneumococci, and penicillin G-sensitive and penicillin G-resistant staphylococci.


Cloxacillin is a semi synthetic antibiotic. It comes under the same class as penicillin. Thus, it is used to treat staphylococci that produce beta-lactamase.

What should I know before taking this drug

How to take it

Cloxacillin is a prescription drug, thus, should be taken exactly as directed by the physician. In case of any doubt, speak to your doctor or pharmacist. Each dose of Cloxacillin should be taken with a full glass of water.

The drug is usually taken on an empty stomach an hour before or 2 hours after meals. Never drink beverages like juice or soda with the dose of Cloxacillin. This tends to decrease the effectiveness of the drug.

Make sure the dose of Cloxacillin is properly spaced. This will help maintain the level of the drug in the blood all through the day. Thus, help treat the infection quickly.

Never crush, chew or open the capsules. Always swallow the capsules whole.

In case of suspension, shake well before use. Measure the liquid form with a measuring spoon or cup. Make sure you take the correct dose to make the drug effective.

Complete the dose as advised by the doctor, even if you feel better. The symptoms might disappear, but the infection might linger in the blood.

Adverse reactions/side effects

Some of the side effects of the drug include:

  • Diarrhea
  • Gas
  • Upper abdominal pain
  • Nausea/vomiting
  • Allergic reaction like shortness of breath, hives, swelling of lips, mouth, face, tongue, skin rash or fainting

If you develop some of the following side effects, contact the doctor immediately.

  • Severe watery or bloody diarrhea
  • Sore tongue or mouth or black, hairy tongue
  • Yellowing of eyes or skin
  • Swelling, redness, pain or warmth at the site of injection (in case of injectible)
  • White patches on the tongue (oral thrush)
  • When not to take the medicine

Those who have had an allergic reaction to penicillin or cephalosporin should avoid taking Cloxacillin. Tell your doctor is you suffer from any kidney disease, stomach infection or intestinal disease. Patients of infectious mononucleosis should also avoid the drug as the risks of infection increases.

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The safety of the drug given to children under the age of 1 year is still not established. Thus, avoid giving the drug to infants.

Geriatric use

Use of the drug in older individuals shows similar effects as in younger patients.

Pregnant women

The drug belongs to FDA Pregnancy Category B. This means the drug is safe to use in pregnancy. However, never take the drug without discussing with your doctor, when you are pregnant.

Lactating women

There are no reports or studies that prove Cloxacillin passes through breast milk. Thus, discuss with your doctor before taking the drug, if you are breast-feeding a baby.

What should I do if

I miss dose(s)

In case you miss a dose, take the dose immediately after you remember. If it is time for the other dose, skip the one missed. Never take a double dose, unless advised by the doctor.

I take over dose

In case of overdose, seek medical attention immediately. Symptoms of overdose include loss of feeling in fingers and toes, pain, muscle weakness, seizures, confusion, agitation as well coma in severe cases.

What to discuss with doctor/pharmacist

Drug interactions

Some medications may decrease the effectiveness of Cloxacillin. Make sure you inform your doctor, if you are on:

  • Cholestyramine/colestopol
  • Erythromycin, tetracycline, microcycline, doxycycline
  • Birth control pills as Cloxacillin may decrease the effectiveness of these drugs
  • Methotrexate, as Cloxacillin may increase the effects of this drug, thus requiring a dose adjustment
  • Allopurinol, as Cloxacillin may increase the side effects of this drug leading to a skin rash
  • Probenecid, as this drug increases the effects of Cloxacillin, thus requiring a dose adjustment.

Other drugs and supplements may also interact with Cloxacillin. Thus, discuss all the drugs you are taking with your doctor.

Dosage form

It is available in form of tablets, capsules, liquid as well as an intramuscular injection.


The dose for adult patients with upper RTI includes 250 mg orally every 6 hours for 1 to 2 weeks. The maximum dose in this case is 4g/day.

The dose for adult patients with pneumonia includes 500 mg orally every 6 hours for about 21 days. The maximum dose is 4g/day.

Patients with cystitis are given 250 mg every 6 hours for 3 to 7 days. Skin infections are treated with 500 mg of Cloxacillin orally every 6 hours for a week or for 3 days after the acute inflammation resolves.

Children over 1 year of age up to 18 years suffering from pneumonia, upper RTI or skin infections are given 50 to 100 mg/kg/day divided over the period of 6 hours.


Store the capsules at room temperature and the suspension in refrigerator. The suspension is good to use for 14 days after storage in refrigerator. Keep away from children and pets.

Written by: team

Date last updated: June 08, 2015