Flopen - Dosage | Interactions | Adverse reactions

This article was medically reviewed by M.Pharm, Marko Tanaskovic on August 12, 2018. To read more about an author, click here.

Flopen is a medicine that contains active substance called flucloxacillin and is available on the Australian market. It belongs to the family of penicillins derived from isoxazole. It exhibits a strong bactericidal effects on Gram-positive bacteria including bacteria synthesizing an enzyme called beta-lactamase which hydrolyze penicillin antibiotics - this is common cause of antibiotic resistance.

Flopen is indicated for the treatment of the following infections if they are caused by susceptible bacteria:

  • Cellulitis.
  • Skin ulcer.
  • Skin abscess.
  • Impetigo (a skin infection caused by staphylococci or streptococci - occurs mostly in children).
  • Erysipelas (also known as red wind - a severe skin infection caused by Group A beta-hemolytic streptococcus).
  • Infected wounds or burns.
  • Upper respiratory tract infections (sinusitis, tonsillitis and pharyngitis).
  • Pneumonia (inflammation of the lung).
  • Otitis media (middle ear inflammation).
  • Urinary tract infections.
  • Endocarditis (inflammation of the heart's endocardium).
  • Osteomyelitis (infection and inflammation that affects bone marrow).
  • Meningitis (infection and inflammation that affects brain).

Sometimes this medicine is used for preventive purposes in order to prevent the occurrence of infections in patients undergoing cardiothoracic surgery.


Flopen is associated with acute attacks of porphyria, and therefore its use must be avoided in patients who already have porphyria (a genetic disease characterized by heme metabolism disorder).

There have been reported cases of cholestatic liver damage induced by this drug, which is why this medicine should not be used in patients who have a history of cholestatic jaundice induced by flucloxacillin. If you notice symptoms and signs of liver damage, such as: pain in the upper right abdominal quadrant, loss of appetite, nausea and jaundice, you should contact your doctor immediately.

Studies have shown that flucloxacillin displace bilirubin from plasma protein binding sites, which increases the risk of jaundice in the newborn. Therefore, it must be used very cautiously in infants.

As with other penicillins, Flopen can also cause an allergic reaction, and patients who have a known allergic reaction to penicillins or cephalosporins should not use this medicine.

If you have a severe, prolonged diarrhea, contact your doctor immediately as this may be a symptom of pseudomembranous colitis (life-threatening infection and inflammation of the bowel).

If it is used for extended periods of time, then liver and kidney function should be regularly monitored during therapy.

Flopen, Pregnancy and Breastfeeding

Animal studies have not shown teratogenic effects. There are limited studies on the use of this medicine during human pregnancy, and these studies have not revealed any adverse reactions. However, the decision to use Flopen during pregnancy can only be made by your doctor following a careful assessment of the benefit / risk ratio for both, mother and unborn child.

Since small amounts of this drug are detected in breast milk which can cause diarrhea in infants, your doctor will decide whether to discontinue breastfeeding or therapy.


Flopen exists in the form of capsules intended for oral administration at a dosage of 500 mg and 250 mg.

The usual dose for adult patients is 250 mg every 6 hours for most indications. In the treatment of severe infections (e.g. osteomyelitis or endocarditis), the dose can be increased up to 8000 mg divided into 3 or 4 doses.

In children aged 2-10, the dose should be reduced by 50% while in children under the age of 2, the dose should be reduced by 75%.

Your doctor will determine which dosage is best for you.


Flopen may increase the plasma concentration of the following drugs, which increases the risk of side effects:

  • Indomethacin (non-steroidal anti-inflammatory drug).
  • Probenecid (a medicine used to treat gout).
  • Acetylsalicylic acid, also known as Aspirin.

Flopen decrease effectiveness of oral contraceptives, which is why the simultaneous application must be avoided.

Adverse reactions

Flopen may cause the following adverse reactions:

  • Weight loss.
  • Nausea and vomiting.
  • Disorientation.
  • Interstitial nephritis.
  • Cholestatic liver damage.
  • Jaundice.
  • Urticaria.
  • Stevens-Johnson syndrome and erythema multiforme.
  • Diarrhea, including pseudomembranous colitis.
  • Inflammation of the joints and muscles.
  • Arrhythmia.
  • Difficulty breathing.
  • Dyspepsia.
  • Fever.
  • Neutropenia.
  • Agranulocytosis.
  • Anaphylactic reaction.


  1. medicines link
  2. NCBI

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