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Drug Nomenclature

International Nonproprietary Names (INNs) in main languages (French, Latin, Russian, and Spanish):

Synonyms: BRL-2039; Flucloxacilina; Flucloxacillinum; Flukloksasilliini; Flukloxacillin
BAN: Flucloxacillin
USAN: Floxacillin
INN: Flucloxacillin [rINN (en)]
INN: Flucloxacilina [rINN (es)]
INN: Flucloxacilline [rINN (fr)]
INN: Flucloxacillinum [rINN (la)]
INN: Флуклоксациллин [rINN (ru)]
Chemical name: (6R)-6-[3-(2-Chloro-6-fluorophenyl)-5-methylisoxazole-4-carboxamido]penicillanic acid
Molecular formula: C19H17ClFN3O5S =453.9
CAS: 5250-39-5
ATC code: J01CF05
Read code: y02HX

Note. Compounded preparations of flucloxacillin may be represented by the following names: Co-fluampicil (BAN)—flucloxacillin 1 part and ampicillin 1 part (w/w).

Flucloxacillin Magnesium

(British Approved Name Modified, rINNM)

Drug Nomenclature

INNs in main languages (French, Latin, Russian, and Spanish):

BAN: Flucloxacillin Magnesium [BANM]
INN: Flucloxacillin Magnesium [rINNM (en)]
INN: Flucloxacilina magnésica [rINNM (es)]
INN: Flucloxacilline Magnesique [rINNM (fr)]
INN: Magnesii Flucloxacillinum [rINNM (la)]
INN: Магния Флуклоксациллин [rINNM (ru)]
Molecular formula: (C19H16ClFN3O5S)2Mg,8H2O =1074.2
CAS: 58486-36-5
ATC code: J01CF05

Pharmacopoeias. In Europe. European Pharmacopoeia, 6th ed., 2008 and Supplements 6.1 and 6.2 (Flucloxacillin Magnesium Octahydnate). A white or almost white, crystalline powder. Slightly soluble in water; freely soluble in methyl alcohol. A 0.5% solution in water has a pH of 4.5 to 6.5.

Flucloxacillin Sodium

(British Approved Name Modified, rINNM)

Drug Nomenclature

INNs in main languages (French, Latin, Russian, and Spanish):

Synonyms: Flucloxacilina sódica; Flucloxacillinum Natricum; Flucloxacillinum Natricum Monohydricum; Flukloksacilino natrio druska; Flukloksasilliininatrium; Flukloxacilin sodná sůl monohydrát; Flukloxacillin-nátrium; Flukloxacillinnatrium
BAN: Flucloxacillin Sodium [BANM]
INN: Flucloxacillin Sodium [rINNM (en)]
INN: Flucloxacilina sódica [rINNM (es)]
INN: Flucloxacilline Sodique [rINNM (fr)]
INN: Natrii Flucloxacillinum [rINNM (la)]
INN: Натрий Флуклоксациллин [rINNM (ru)]
Molecular formula: C19H16ClFN3NaO5S,H2O =493.9
CAS: 1847-24-1
ATC code: J01CF05

Pharmacopoeias. In Europe. European Pharmacopoeia, 6th ed., 2008 and Supplements 6.1 and 6.2 (Flucloxacillin Sodium). A white or almost white, crystalline hygroscopic, powder. Freely soluble in water and in methyl alcohol; soluble in alcohol. A 10% solution in water has a pH of 5.0 to 7.0. Store at a temperature not exceeding 25° in airtight containers. Incompatibility. As with other penicillins, flucloxacillin sodium is incompatible with aminoglycosides.

Adverse Effects and Precautions

As for Benzylpenicillin. Hepatitis and cholestatic jaundice have been reported occasionally with flucloxacillin and may be delayed in onset for up to 2 months after treatment has been stopped; older patients and those receiving flucloxacillin for more than 2 weeks are at greater risk. Fatalities have occurred, usually in patients with serious underlying hepatic disease. There have been rare reports of erythema multiforme, Stevens-Johnson syndrome, and toxic epidermal necrolysis associated with flucloxacillin. Agranulocytosis and neutropenia have been associated rarely with isoxazolyl penicillins such as flucloxacillin. Phlebitis has followed intravenous infusion.

Effects on the liver

 In October 2004, the UK CSM issued a reminder that flucloxacillin is associated rarely with an increased risk of hepatitis and cholestatic jaundice. In some patients, almost always those with serious underlying hepatic disease, fatalities have occurred. The onset of hepatic adverse effects may be delayed for up to 2 months after stopping treatment, and is not related to the dose or to the route. Older patients and those receiving flucloxacillin for more than 2 weeks are at increased risk. Flucloxacillin should not be used in patients with a history of hepatic dysfunction related to its use, and should be used only with caution in patients with evidence of other hepatic impairment. Careful enquiry should be made concerning previous hypersensitivity to beta lactams. A cohort study using UK prescription data found that the risk of developing cholestatic liver disease in the 45 days after starting flucloxacillin was 8.5 per 100 000. In contrast to other countries, flucloxacillin continued to be seen as a first-line drug in the UK.


Flucloxacillin has been associated with acute attacks of porphyria and is considered unsafe in porphyric patients.

Sodium content

Each g of flucloxacillin sodium contains about 2 mmol of sodium.


As for Benzylpenicillin.

Antimicrobial Action

Flucloxacillin is bactericidal with a mode of action similar to that of benzylpenicillin, but is resistant to sta-phylococcal penicillinase. It is active therefore against penicillinase-producing and non-penicillinase-producing staphylococci. Its activity against streptococci such as Streptococcus pneumoniae and Str. pyogenes is less than that of benzylpenicillin, but sufficient to be useful when these organisms are present with penicillin-resistant staphylococci. Flucloxacillin is virtually ineffective against Enterococcus faecalis. Resistance. The resistance of staphylococci to flucloxacillin and other penicillinase-resistant penicillins is described under meticillin.


Flucloxacillin is better absorbed from the gastrointestinal tract than cloxacillin, but absorption is reduced by the presence of food in the stomach. After an oral dose of 0.25 to 1 g, in fasting subjects, peak plasma concentrations in about 1 hour are usually in the range of 5 to 15 micrograms/mL. Plasma concentrations after intramuscular injection of flucloxacillin sodium are similar, but peak concentrations are achieved in about 30 minutes. Doubling the dose can double the plasma concentration. About 95% of flucloxacillin in the circulation is bound to plasma proteins. Flucloxacillin has been reported to have a plasma half-life of approximately 1 hour. The half-life is prolonged in neonates. The distribution of flucloxacillin into body tissues and fluids is similar to that of cloxacillin. Flucloxacillin is metabolised to a limited extent and the unchanged drug and metabolites are excreted in the urine by glomerular filtration and renal tubular secretion. About 66% of an oral dose and 76% of a parenteral dose is excreted in the urine within 8 hours. Only small amounts are excreted in the bile. Flucloxacillin is not removed by haemodialysis or peritoneal dialysis. Plasma concentrations are enhanced by probenecid.

Uses and Administration

Flucloxacillin is an isoxazolyl penicillin used primarily for the treatment of infections due to staphylococci resistant to benzylpenicillin. These include bone and joint infections, endocarditis, pneumonia, skin infections (including soft-tissue infections), and toxic shock syndrome. For discussions of these infections and their treatment, see under Choice of Antibacterial. Administration and dosage. Flucloxacillin is given parenterally and orally as the sodium or magnesium salt. All doses are expressed as flucloxacillin; 1.18 g of flucloxacillin magnesium and 1.09 g of flucloxacillin sodium are each equivalent to about 1 g of flucloxacillin. Oral doses should be taken at least 30 minutes before meals as the presence of food in the stomach reduces absorption. In severe renal impairment a reduction in dosage may be necessary. The usual adult dose orally or by intramuscular injection is 250 mg four times daily. It is given intravenously in a dose of 0.25 to 1 g four times daily by slow injection over 3 to 4 minutes or by intravenous infusion. All systemic doses may be doubled in severe infections. Up to 8 g daily in 3 or 4 divided doses may be given for osteomyelitis; in endocarditis a dose of 8 g daily in 4 divided doses may be given to patients weighing up to 85 kg, and 12 g daily in 6 divided doses may be used in those weighing more. Flucloxacillin has been given by other routes in conjunction with systemic therapy. It has been given in a dose of 250 to 500 mg daily by intra-articular injection, dissolved if necessary in a 0.5% solution of lidocaine hydrochloride, or by intrapleural injection in a dose of 250 mg daily. Using powder for injection, 125 to 250 mg has been dissolved in 3 niL of sterile water and inhaled by nebuliser 4 times daily. Children up to 2 years of age may be given one-quarter the adult dose and those aged 2 to 10 years one-half the adult dose. Flucloxacillin may be used with other antibacterials, including ampicillin (known as co-fluampicil), to produce a wider spectrum of activity. If flucloxacillin is given with an aminoglycoside the two drugs should not be mixed.


British Pharmacopoeia 2008: Co-fluampicil Capsules: Co-fluampicil Oral Suspension: Flucloxacillin Capsules: Flucloxacillin Injection: Flucloxacillin Oral Solution: Flucloxacillin Oral Suspension.

Proprietary Preparations

Australia: Flopen: Floxapen: Floxsig: Flubiclox: Flucil: Staphylex: Austria: Floxapen: Belgium: Floxapen: Staphycid: Chile: Fluxacina: Vitalpen: Denmark: Heracillin: Germany: Fluclox: Fludoxa: Staphylex: Hong Kong: Flucloxil India: Floxapenf: Indonesia: Floxapen: Ireland: Floxapen: Flucillin: Fluclon: Geriflox: Italy: Betabiotic: Cloxillin: Evercid: Faifloc: Fareclox: Flucacid Flucef: Flucinal Fluclox: Fluxacil: Fluzerit: Liderclox: Nepenic: Pantaflux: Recaflux: Malaysia: Staphlex: Mexico: Floxapen: The Netherlands: Floxapen: Stafoxili; New Zealand: Floxapen: Flucloxin: Staphlex: Philippines: Stafloxin: Portugal: Floxapen: Floxili; South Africa: Floxapen: Singapore: Staphlex: Sweden: Heracillin: Switzerland: Floxapen: Thailand: Staphycid: Turkey: Flix: Floksin UK: Floxapen: Fluclomix: Ladropen: Venezuela: Floxapen.


Germany: Flanamox: South Africa: Macropen: Megapen: Suprapen: UK: Magnapen.


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