Drug information of Carbenicillin


Drug group:

Carbenicillin is an antibiotic in the penicillin group of drugs. It fights bacteria in your body. Carbenicillin is used to treat many different types of infections caused by bacteria, such as bladder infection.

Mechanism of effect

Carbenicillin exerts its antibacterial activity by interference with final cell wall synthesis of susceptible bacteria. Penicillins acylate the penicillin-sensitive transpeptidase C-terminal domain by opening the lactam ring. This inactivation of the enzyme prevents the formation of a cross-link of two linear peptidoglycan strands, inhibiting the third and last stage of bacterial cell wall synthesis. Cell lysis is then mediated by bacterial cell wall autolytic enzymes such as autolysins; it is possible that carbenicillin interferes with an autolysin inhibitor.


Carbenicillin is a semisynthetic penicillin. Though carbenicillin provides substantial in vitro activity against a variety of both gram-positive and gram-negative microorganisms, the most important aspect of its profile is in its antipseudomonal and antiproteal activity. Because of the high urine levels obtained following administration, carbenicillin has demonstrated clinical efficacy in urinary infections due to susceptible strains of: Escherichia coli, Proteus mirabilis, Proteus vulgaris, Morganella morganii, Pseudomonas species, Providencia rettgeri, Enterobacter species, and Enterococci (S. faecalis).


Rapidly absorbed from the small intestine following oral administration. Oral bioavailability is 30 to 40%. Volume of distribution is not Available. Protein binding is 30 to 60%. Metabolism is Minimal. Route of elimination is not Available. Half life is 1 hour.

Drug indications

For the treatment of acute and chronic infections of the upper and lower urinary tract and in asymptomatic bacteriuria due to susceptible strains of bacteria.


Usual Adult Dose for Cystitis

382 to 764 mg (1 to 2 tablets) orally 4 times a day for 3 to 7 days (Escherichia coli, Proteus, or Enterobacter as causative agent).

764 mg (2 tablets) orally 4 times a day for 3 to 7 days (Pseudomonas or Enterococcus as causative agent).

Usual Adult Dose for Prostatitis

764 mg (2 tablets) orally 4 times a day for 14 days. Chronic prostatitis may require 1 to 3 months of antimicrobial therapy.

Side effects

Diarrhea , Headache , nausea , dry mouth , vomiting , urticaria , fever , anorexia , rectal hemorrhage , itching , flatulence , thrombocytopenia , vaginitis , Rash , Hypocalcemia , itchy eyes

• Gastrointestinal side effects have included nausea, vomiting, diarrhea, bad taste, flatulence, glossitis, abdominal cramps, dry mouth, furry tongue, rectal bleeding, anorexia, loose stools, and epigastric distress. Pseudomembranous colitis has been reported rarely.
• Hypersensitivity reactions have included anaphylaxis, rash, urticaria, pruritus, fever, and eosinophilia.
• Hematologic side effects have included anemia, thrombocytopenia, leukopenia, neutropenia, and eosinophilia. Carbenicillin affects platelet aggregation and bleeding may occur.
• Cardiovascular side effects may include congestive heart failure resulting from the sodium content of carbenicillin.
• Metabolic side effects may include hypokalemia.
• Hepatic side effects have included mild elevations of liver transaminases.
• Genitourinary side effects have included vaginitis.
• Other side effects have included itchy eyes and headache.

• The serum concentration of Amikacin can be decreased when it is combined with Carbenicillin.
• The therapeutic efficacy of BCG vaccine can be decreased when used in combination with Carbenicillin.
• The serum concentration of Doxorubicin can be decreased when it is combined with Carbenicillin.
• The therapeutic efficacy of Carbenicillin can be decreased when used in combination with Doxycycline.
• The serum concentration of Gentamicin can be decreased when it is combined with Carbenicillin.
• The serum concentration of Idarubicin can be decreased when it is combined with Carbenicillin.
• The serum concentration of the active metabolites of Mycophenolic acid can be reduced when Mycophenolic acid is used in combination with Carbenicillin resulting in a loss in efficacy.
• The serum concentration of Methotrexate can be increased when it is combined with Carbenicillin.
• The serum concentration of Carbenicillin can be increased when it is combined with Probenecid.
• Carbenicillin may increase the anticoagulant activities of Warfarin.
• The serum concentration of Spectinomycin can be decreased when it is combined with Carbenicillin.


Serious and occasionally fatal hypersensitivity reactions have been reported with antibiotics. The drug should be discontinued immediately at the first appearance of a skin rash or other signs of hypersensitivity. Severe, acute hypersensitivity reactions may require treatment with adrenaline and other resuscitative measures including oxygen, intravenous fluids, antihistamines, corticosteroids, cardiovascular support and airway management as clinically indicated.

Clostridium difficile associated diarrhea (CDAD) has been reported with almost all antibiotics and may potentially be life-threatening. Therefore, it is important to consider this diagnosis in patients who present with diarrhea following carbenicillin therapy. Mild cases generally improve with discontinuation of the drug, while severe cases may require supportive therapy and treatment with an antimicrobial agent effective against C difficile. Hypertoxin producing strains of C difficile cause increased morbidity and mortality; these infections can be resistant to antimicrobial treatment and may necessitate colectomy.

Dose reductions are recommended in patients with severe renal impairment (creatinine clearance less than 20 mL/min). Carbenicillin will not reach adequate urine concentrations in patients with creatinine clearance less than 10 mL/min.

Superinfection with nonsusceptible organisms (i.e., yeasts) may occur with prolonged therapy.

Periodic monitoring of renal and hematologic function is recommended during prolonged therapy.

To reduce the risk of development of drug-resistant organisms, antibiotics should only be used to treat or prevent proven or suspected infections caused by susceptible bacteria. Culture and susceptibility information should be considered when selecting treatment or, if no data are available, local epidemiology and susceptibility patterns may be considered when selecting empiric therapy. Patients should be advised to avoid missing doses and to complete the entire course of therapy.

Points of recommendation

Do not use this medication if you are allergic to carbenicillin or to any other penicillin antibiotic, such as:

  • amoxicillin
  • ampicillin ;
  • dicloxacillin
  • oxacillin  or
  • penicillin

Before using carbenicillin, tell your doctor if you are allergic to any drugs (especially cephalosporins such as Ceclor, Ceftin, Duricef, Keflex, and others), or if you have:

  • asthma;
  • kidney disease;
  • a bleeding or blood clotting disorder;
  • a history of diarrhea caused by taking antibiotics; or
  • a history of any type of allergy.

If you have any of these conditions, you may need a dose adjustment or special tests to safely take carbenicillin.

FDA pregnancy category B. This medication is not expected to be harmful to an unborn baby. Tell your doctor if you are pregnant or plan to become pregnant during treatment.

Carbenicillin can make birth control pills less effective, which may result in pregnancy. Before taking carbenicillin, tell your doctor if you use birth control pills.

Carbenicillin can pass into breast milk and may harm a nursing baby. Do not use this medication without telling your doctor if you are breast-feeding a baby. 

Take the medicine with a full glass of water.

Carbenicillin should be taken on an empty stomach, at least 1 hour before or 2 hours after eating a meal.

To be sure this medication is helping your condition, your blood will need to be tested on a regular basis. Your kidney or liver function may also need to be tested. Do not miss any scheduled visits to your doctor.

Take this medication for the entire length of time prescribed by your doctor. Your symptoms may get better before the infection is completely treated. Carbenicillin will not treat a viral infection such as the common cold or flu.

Do not give carbenicillin to another person, even if they have the same symptoms you have.

This medication can cause you to have unusual results with certain medical tests. Tell any doctor who treats you that you are using carbenicillin.

Store carbenicillin at room temperature away from moisture, heat, and light. 

Take the missed dose as soon as you remember. If it is almost time for your next dose, skip the missed dose and take the medicine at your next regularly scheduled time. Do not take extra medicine to make up the missed dose.

Pregnancy level


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