Flucillin

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Flucillin

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Medically reviewed

Laura Arias

Last updated on 22/12/2025

This page provides general, reference-level information compiled from official medical sources. It is not a substitute for professional medical advice, diagnosis, or treatment. For decisions about your health, please consult a qualified healthcare professional.

Overview of Flucillin

Flucillin is the trade name for a medicine containing the active ingredient flucloxacillin. This agent is classified as a semisynthetic penicillin and belongs to the larger β-lactam antibiotic pharmacological class. It is primarily administered for the general treatment of bacterial infections.

Property Description
Active ingredient Flucloxacillin (Sodium Salt)
Form Capsule, Powder for oral solution, Injection
Pharmacological class β-Lactam Antibiotic
Common use Treating bacterial infections
Origin Semisynthetic

What Type of Medicine is Flucillin? (Identity and Classification)

Flucillin is a semisynthetic antibiotic of the penicillin type, specifically identified by its active ingredient, flucloxacillin (INN). The compound is classified as a narrow-spectrum antibiotic that belongs to the β-lactam antibiotic group, which is structurally defined by the presence of a beta-lactam ring. It is a single-agent product that was chemically modified from the natural penicillin nucleus to enhance its properties.

The general purpose of this medication is to exert a bactericidal effect against susceptible organisms, particularly Gram-positive organisms. An analysis of the medicine's profile confirms its role in the treatment of bacterial infections caused by susceptible strains. Pharmacological studies support the clinical recognition of flucloxacillin's effectiveness in managing infections where staphylococci are suspected.


What is the Composition and Origin of Flucillin? (Composition and Forms)

The composition of Flucillin centers on its main component, flucloxacillin, typically formulated as flucloxacillin sodium. Being semisynthetic, the compound originates from a natural source but is chemically enhanced for pharmaceutical use, making the active ingredient acid-stable.

Flucloxacillin is available in multiple dosage forms, including capsules and powder for oral solution (suspension) for oral consumption, and a sterile powder for solution for injection for parenteral delivery. Flucloxacillin is recognized for its effectiveness and safety in multiple forms. This confirms that the medication is suitable for both convenient oral use and necessary injection when required.


Why is Flucloxacillin β-Lactamase Resistant? (Core Mechanism Feature)

Flucloxacillin is considered β-lactamase resistant because its unique chemical structure protects it from being destroyed by the β-lactamase enzyme produced by certain defensive bacteria, like staphylococci. This resistance is a crucial feature that allows the medicine to retain its full bactericidal effect where non-resistant penicillins would fail. This essential characteristic is central to its utility, ensuring it can successfully inhibit bacterial cell wall synthesis even when faced with resilient bacterial strains.

Regulatory References

  1. WHO Essential Medicines List Profile

What side effects are possible with Flucillin?

Possible side effects and safety information

The safety profile of Flucillin (flucloxacillin) is documented through official regulatory classifications, detailing possible adverse reactions and specific safety constraints. All factual statements are consistent with official government prescribing information.

Frequency-Classified Adverse Reactions

Adverse reactions are classified by frequency according to regulatory standards:

  • Common effects may include gastrointestinal disturbances (such as nausea and minor diarrhea).
  • Uncommon effects typically involve skin reactions (such as rash or pruritus).
  • Very Rare reactions include serious systemic events such as hepatitis, cholestatic jaundice, severe cutaneous reactions (like Stevens-Johnson Syndrome and Toxic Epidermal Necrolysis), and disorders of the blood and lymphatic system (e.g., neutropenia).

System and Serious Adverse Reactions

The most critical safety constraints involve hypersensitivity reactions, which range up to anaphylaxis and necessitate a contraindication for individuals with a known history of penicillin allergy. Reactions are classified across several System-Organ Classes, with key involvement of the Hepatobiliary system and the Skin and subcutaneous tissue.

Population-Specific Safety Notes

The official labeling notes that the risk profile is altered in specific populations. Caution is required in patients with pre-existing renal impairment due to the risk of CNS effects at high plasma concentrations. Older adults may have an increased risk of severe hepatotoxicity, which can have a delayed onset, sometimes appearing several weeks after treatment has ceased. The medicine is contraindicated in patients with a history of flucloxacillin-associated hepatic dysfunction or jaundice.

Overdose and Emergency Response

Overdose and When to Seek Help

The official regulatory profile for a Flucillin (flucloxacillin) overdose is defined by the risk of systemic toxicities, particularly following exposure to high doses. Documented acute manifestations include severe gastrointestinal effects such as persistent diarrhoea and vomiting.

More critically, overdose may result in neurotoxicity, presenting as encephalopathy, agitation, or convulsions (seizures), which can progress to coma in severe cases. High exposure is also associated with electrolyte disturbances, specifically hypokalaemia (low potassium), and blood disorders like neutropenia.

Required Emergency Action

Regulatory documents are explicit regarding the need for immediate medical attention if an overdose is suspected, even if the person does not exhibit symptoms of discomfort. Urgent professional intervention is mandated because no specific antidote is known; the management required is strictly symptomatic treatment and close monitoring of renal and electrolyte function.

Special considerations exist for patients with poor renal function and newborns due to an officially noted increased risk of severe outcomes, including kernicterus in jaundiced infants.

Therapeutic Uses of Flucillin

What Flucillin Treats: Main Uses and Benefits

The primary therapeutic use of Flucillin (flucloxacillin) is relevant in conditions involving specific bacterial infections where the pathogen is susceptible to this narrow-spectrum penicillin. This medicine is commonly used to manage a wide variety of bacterial infections.

Flucillin supports the management of conditions presenting with symptoms related to inflammatory or irritative states in the skin, soft tissues, bones, and blood. It is applied in addressing symptom clusters associated with infections such as significant cellulitis, impetigo, osteomyelitis, and severe systemic infections like sepsis or endocarditis. The medication may assist with maintaining functional stability by addressing the infection, which supports general well-being during symptomatic phases. It is relevant for easing symptoms like intense redness, swelling, and pus formation that interfere with daily comfort. The medication contributes to improved comfort during periods of heightened symptoms and assists with maintaining functional stability.

Quick Fact: Support for Symptoms Related to Inflammatory States This medication is commonly used across conditions presenting with acute episodes where symptoms related to physical discomfort or systemic imbalance require supportive management.

Eligibility and Restrictions for Use

Who can and cannot use Flucillin?

This information is based strictly on the official eligibility profiles documented by regulatory authorities and defines the required constraints for use.


Populations Who Must Not Use Flucillin (Contraindications)

  • Known Hypersensitivity: Individuals with a history of allergy or anaphylaxis to flucloxacillin or any other beta-lactam antibiotics, including penicillins and cephalosporins.
  • Prior Liver Reaction: Patients with a documented history of jaundice or other hepatic dysfunction that was previously associated with taking flucloxacillin (or dicloxacillin).
  • Ocular Use: The medicine is contraindicated for administration into the eye (ocular or subconjunctival use).

Populations Requiring Special Caution

  • Newborns (Neonates): Use in jaundiced newborns and neonates requires special caution because the drug can displace bilirubin, potentially leading to kernicterus.
  • Hepatic Impairment: Caution is necessary in patients with existing evidence of hepatic dysfunction.
  • Elderly Patients: Individuals 50 years of age and older are advised caution due to a documented higher risk of severe liver events.
  • Pregnancy and Lactation: Use during pregnancy should be reserved for essential cases. It may be administered during lactation, but the possibility of sensitisation in the infant should be considered.

Official regulatory documents define these constraints to exclude individuals who face the highest risk of severe adverse events and to ensure the medicine is only used under appropriate clinical consideration in vulnerable groups.

What should I know about interactions with other medicines?

Interactions with other medicines and products

Flucillin (Flucloxacillin) can interact with several other medicines, requiring careful monitoring or dose adjustments. It is important to inform your healthcare provider about all medicines you are taking, including over-the-counter products.

Clinically Significant Interactions

Interacting Medicine Potential Effect
Warfarin (or other Vitamin K Antagonists) Flucloxacillin can significantly decrease the anticoagulant effect of Warfarin, leading to a risk of subtherapeutic anticoagulation. Close and frequent monitoring of your International Normalized Ratio (INR) is essential during and after Flucloxacillin use.
Voriconazole (or other Azole Antifungals) Flucloxacillin can substantially lower the concentration of Voriconazole in the blood, potentially making the antifungal treatment less effective. Dose adjustment or therapeutic drug monitoring of Voriconazole may be necessary.
Paracetamol (Acetaminophen) Concurrent use, particularly in patients with risk factors like severe kidney problems or malnutrition, has been associated with a rare but serious risk of high anion gap metabolic acidosis (HAGMA). Close monitoring for acid-base disorders is recommended.
Methotrexate Flucloxacillin may reduce the excretion of Methotrexate, which can increase the risk of Methotrexate toxicity.
Probenecid (for gout) Probenecid can delay the body's removal of Flucloxacillin, which may result in higher blood levels of Flucloxacillin.
Oral Contraceptives Flucloxacillin may potentially reduce the efficacy of combined oral contraceptives (birth control pills). Additional non-hormonal contraception may be advised during and for seven days after treatment.

Mechanism of Action

Targeting the Essential Bacterial Cell Wall Assembly

Flucloxacillin's action begins by targeting bacterial enzymes called Penicillin-Binding Proteins (PBPs), which are essential for building the rigid peptidoglycan layer of the cell wall. The drug binds irreversibly to and inhibits the function of these enzymes, stopping the final cross-linking process necessary for structural integrity. This mechanical failure leads to the activation of the cell’s internal destructive enzymes, causing rapid and complete bacterial cell lysis (breakdown).


Evasion of Bacterial Defense Mechanisms

The flucloxacillin molecular structure is able to circumvent a specific form of bacterial defense: the secretion of the enzyme beta-lactamase. The drug's side chains prevent this enzyme from destroying the core beta-lactam structure, which preserves the drug's activity against strains that produce this defense. This preserved function allows the cell wall disruption mechanism to proceed unimpeded, leading to the bactericidal effect even in the presence of these resistant organisms.


Constraints on the Inhibitory Mechanism

The drug's mechanism is limited by the binding affinity of the target enzymes. If the bacterium produces an altered PBP structure—such as PBP2a in MRSA—the drug cannot bind effectively. This structural constraint functionally overrides the drug’s inhibitory action, preventing the lytic cascade and leading to a failure of the physiological bacteria-killing effect.

Dosage and Administration Information

How to Use Flucillin

Flucillin (flucloxacillin) is administered through multiple official routes, including oral consumption via capsules or oral solution, and parenteral delivery via intravenous (IV) or intramuscular (IM) injection. The selection of the route is based on the severity of the infection and the patient’s clinical status.


Standard Dosing and Administration Schedule

Usage Aspect Official Instruction Summary
Adult Dose Range Typically 250 mg to 500 mg per dose. In severe systemic infections, the dose may be increased up to 1 g per dose.
Dosing Frequency Administered in divided doses approximately four times a day, maintaining an interval of every six hours.
Oral Timing Oral forms must be taken on an empty stomach to ensure maximum absorption. This means ingestion must occur 30 to 60 minutes before meals or no sooner than two hours after eating.
Preparation Powder for injection must be reconstituted with the specified diluent before being administered as a slow IV injection or infusion over several minutes.
Renal Adjustment For patients with severe renal impairment (creatinine clearance < 10 mL/min), a reduction in dose or extension of the dose interval (e.g., to 8–12 hours) is required to prevent accumulation.

The typical duration of treatment for common infections is generally 7 to 14 days, though the required duration is determined by the specific type and site of the infection being addressed. If a dose is missed, it is generally advised to take it as soon as remembered, unless it is close to the time for the next scheduled dose, in which case the missed dose should be skipped to maintain the regular schedule.

Recent Clinical Evidence

Research Evidence for Flucillin: An Overview

This section explains what the research evidence shows about Flucillin (flucloxacillin), focusing on the types of studies that have been conducted and the nature of the findings reported in official and peer-reviewed sources. It is important to remember that this research describes group patterns, not personal outcomes. The evidence highlights what is known—and what is still uncertain—about this medicine.


Evidence for Use in Skin and Soft Tissue Infections

Flucillin was studied for its role in acute skin and soft tissue infections (SSTIs), such as cellulitis and impetigo. Research primarily includes Randomized Controlled Trials (RCTs) and various large-scale Observational Studies.

Researchers conducted these studies used in research exploring how symptoms change over time. They monitored outcomes linked to inflammatory or irritative states, such as measuring the change in the size of the infected area and the patient-reported time to clinical change. Studies reported how symptoms evolved in the observed populations, noting patterns observed regarding the measured change in the clinical state. Follow-up durations were limited in many studies, typically focusing only on the acute phase.


Evidence for Use in Deep-Seated and Systemic Infections

Research related to more serious, deep-seated, or systemic infections—such as bloodstream infections and bone infections—is structured around primarily Prospective Observational Studies and Retrospective Reviews.

Studies examined outcomes related to systemic or functional imbalance, including outcomes related to survival (e.g., 30-day mortality) and whether the bacteria persisted in the bloodstream. Researchers also monitored pharmacological markers that examine drug concentration in the body. Research has explored achieving specific drug levels as a factor associated with patterns of clinical outcomes in these conditions. However, studies also reported that findings were mixed regarding the consistency of drug levels across all observed patients.


Areas of Research Uncertainty and Gaps

The available evidence contributes to the broader evidence landscape, but it also highlights several areas where certainty remains low. Limited information for long-term outcomes is a key finding, as most studies focus on the short-term change of the acute infection, and the long-term effects of this treatment are not fully established. Furthermore, comparative evidence is lacking from large-scale, masked Randomized Controlled Trials that directly compare the clinical outcomes of Flucillin over other agents.

Key Studies & References

  1. Flucloxacillin 500mg Powder for Solution for Injection - Summary of Product Characteristics (SmPC) (eMC)
  2. Summary of the evidence | Cellulitis and erysipelas: antimicrobial prescribing - NICE guideline NG141

Frequently Asked Questions (FAQ)

Common questions about Flucillin (FAQ)


Q: Is it normal to feel a little dizzy when taking Flucillin?

Dizziness is mentioned in some official patient information leaflets as a possible side effect of Flucillin, though it is not a frequently reported event. Because dizziness can potentially affect the ability to drive or use machinery, official guidance often suggests caution, as the effect on an individual is only known after use.


Q: Does Flucillin reduce the effectiveness of birth control pills?

Regulatory information indicates that Flucillin may potentially reduce the effectiveness of combined oral contraceptives (birth control pills). Due to this possibility, official prescribing information mentions that additional non-hormonal contraception may be recommended by a healthcare professional during the course of treatment and for seven days after the completion of Flucillin.


Q: Why do doctors prescribe Flucillin for skin infections?

Flucillin is officially indicated for treating skin and soft tissue infections. This is because the medicine is indicated for infections caused by susceptible bacteria, such as staphylococci, which are often responsible for these infections. Flucillin is effective against strains that produce a defensive enzyme called beta-lactamase.


Q: Is Flucillin effective against staph infections?

Official product information indicates that Flucillin (flucloxacillin) is active against susceptible staphylococci. This is due to the drug's key feature: it is resistant to staphylococcal penicillinase, an enzyme that certain bacteria produce to destroy many common penicillins. This preserves the drug's intended action against these specific bacteria.


Q: Can I take ibuprofen or paracetamol with Flucillin?

Official information provides specific warnings about taking paracetamol concurrently with Flucillin, especially in patients with certain risk factors, due to a rare but serious risk of acid-base imbalance. Ibuprofen is generally not listed as a clinically significant interacting drug in core regulatory documents. However, it is generally recommended to inform your healthcare provider about all medications being taken.


Q: Is it true that Flucillin is often used for bone infections?

Yes, official regulatory indications include the treatment of osteomyelitis, which is a severe bone infection. For such deep-seated or systemic infections, the medicine may be administered at a higher dosage or for a longer duration than for common skin infections.


Q: Is a headache a common side effect of Flucillin?

Headaches are listed as a possible side effect in some official patient information, but they are generally not classified as a common reaction. Regulatory sources classify side effects based on how frequently they are reported in clinical use.


Q: How long after stopping Flucillin can side effects still appear?

The majority of side effects occur while the medicine is being taken, but severe liver reactions (hepatotoxicity) can have a delayed onset. Official regulatory warnings note that these liver problems, such as jaundice, can sometimes appear up to two months after the course of Flucillin has been completed, particularly in older adults.


Q: Does Flucillin cause yeast infections?

Official patient information leaflets sometimes list thrush (oral or vaginal yeast infection) as a possible side effect. This is a potential risk with many antibiotics, as they can disrupt the natural balance of micro-organisms in the body.


Q: What is the difference in effect if Flucillin is taken with food?

Official administration instructions require that the oral form of Flucillin be taken on an empty stomach. This is because taking the medication with food significantly reduces its absorption into the bloodstream. Reduced absorption may lead to lower drug levels in the bloodstream, which can impact the medication's intended effect against the infection.


Q: Is it normal to feel tired while taking Flucillin?

General tiredness or fatigue is not listed as a common side effect in official regulatory classification. However, a very rare adverse reaction, haemolytic anaemia (a blood disorder), can present with symptoms including unusual tiredness and weakness.


Q: Can I crush or open the Flucillin capsules if I have trouble swallowing?

Official instructions state that Flucillin capsules should be swallowed whole with a full glass of water. They should not be opened, crushed, or chewed, as this may increase the risk of irritation or pain in the esophagus (the tube leading to the stomach).


Q: How can I tell if my infection is responding to Flucillin?

Official guidance states that medical advice should be sought if symptoms have not started to improve within 2 to 3 days of starting treatment or if symptoms worsen. Improvement is typically indicated by a reduction in pain, redness, or fever.


Q: Are there any restrictions on driving or operating machinery while on Flucillin?

Adverse effects on the ability to drive or operate machinery are not commonly expected. However, because Flucillin can cause dizziness in some individuals, official warnings recommend that caution be exercised until the individual understands how the medicine affects them.


Q: What are people usually referring to when they mention 'Flucillin rash'?

A rash is a commonly known skin reaction, categorized as an uncommon side effect in official documents. Regulatory information details that these reactions can range from simple, non-serious rashes to very rare, severe skin reactions that require immediate medical attention.


Q: Does Flucillin treat viral infections like the common cold?

No. Flucloxacillin is classified as an antibiotic and is specifically indicated for the treatment of bacterial infections. Regulatory documents do not support its use against viral illnesses, such as the common cold, flu, or most sore throats.


Q: Can Flucillin be taken with other types of antibiotics?

This medicine is sometimes used alongside other antibiotics, depending on the nature of the infection. However, official prescribing information recommends that combination use always be checked with a healthcare professional, as drug interactions or dose adjustments may be necessary.


Q: Is Flucillin used to prevent infections after surgery?

Yes, official regulatory indications include the use of Flucloxacillin as a prophylactic agent (a preventative measure) during major surgical procedures. This is typically done for operations where there is a risk of bacterial infection, such as cardiothoracic or orthopaedic surgery.


Q: What should I do if I miss a dose of Flucillin?

If a dose is missed, official guidance states that the dose should be taken as soon as it is remembered. However, if it is close to the time for the next scheduled dose, guidance indicates that the missed dose should be skipped to maintain the regular schedule. A double dose should not be taken to make up for the one that was missed.


Q: Are there generic versions of Flucillin available?

Yes. Flucillin is a trade name for the active ingredient, flucloxacillin. Because the active ingredient is a recognized medicine on essential lists worldwide, generic versions of flucloxacillin are widely available from various manufacturers.


Q: What are the typical indications for a course of Flucillin being 7 days?

The full course of treatment typically lasts between 7 to 14 days. Shorter courses, such as 7 days, are generally reserved for less complicated or less severe infections. The exact duration is decided by a healthcare professional based on the specific type and site of the infection being treated.

How should Flucillin be stored and disposed of?

Storage and Disposal of Flucillin (Flucloxacillin)

Official regulatory documents define specific storage and disposal requirements to ensure the product's stability and public safety.

Storage Conditions

Flucloxacillin capsules must be stored in a dry place at a temperature below 25 C and in the original pack. All forms of the medicine must be kept out of the sight and reach of children.

Stability and Handling

Once prepared, liquid forms (oral solutions or injections) must be stored under refrigeration (2 C to 8 C) and discarded after a specific time limit (e.g., 24 hours to 14 days, as labeled). Solutions prepared for injection are intended for single use only.

Disposal

Unused or expired product must be disposed of in accordance with local requirements. The medicine must not be allowed into any sewer or body of water and should be disposed of via approved waste disposal procedures.

Attention! Always consult to a doctor or pharmacist before using pills or medicines.

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