Flustaph

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Medically reviewed

Marina Burgos

Last updated on 10/01/2026

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 Flustaph

Quick Facts

Property Description
Active Ingredient Flucloxacillin (typically as Flucloxacillin sodium)
Forms Capsule, Powder for oral suspension, Injection solution
Pharmacological Class Beta-lactam Antibiotic; Penicillinase-Resistant Penicillin
Common Purpose Elimination of susceptible bacterial infections
Origin Semisynthetic

Flustaph: Classification and Origin

Flustaph is a prescription-only, semisynthetic antibiotic medication belonging to the penicillin class, chemically categorized as an isoxazolyl penicillin. Its active therapeutic component is Flucloxacillin, typically formulated as Flucloxacillin sodium. This structure places it within the high-level Beta-lactam antibiotic category, a class clinically recognized for its reliable performance against specific bacterial strains. The medication is a derivative of the natural penicillin nucleus that has been chemically modified, classifying it as semisynthetic. This advanced composition confers specific advantageous properties, distinguishing it from naturally sourced antibiotics. As a single-ingredient product, Flustaph contains only Flucloxacillin to perform its essential function, which is systemically combating specific bacterial infections.


The Role of Flucloxacillin as a Bactericidal Agent

The general purpose of Flustaph is to eliminate susceptible bacteria, achieving its therapeutic effect through a bactericidal action. The Flucloxacillin compound specifically works by disrupting the formation of the bacteria's protective cell wall as the organisms attempt to multiply. Crucially, Flucloxacillin is classified as a penicillinase-resistant penicillin. This characteristic is vital because it means the compound can successfully counteract enzymes, such as penicillinase (or beta-lactamase), which certain defensive bacteria, like staphylococci, produce to neutralize older penicillins. Flucloxacillin is utilized to manage infections caused by these resistant organisms. This targeted, narrow-spectrum capability makes it a key tool for specific Gram-positive organisms, such as Methicillin-Susceptible Staphylococcus aureus (MSSA).


Available Forms for Flustaph

Flustaph is manufactured in several distinct dosage forms to suit varying clinical needs. These preparations include capsules and powder for oral suspension, as well as powder for solution for injection (parenteral forms). The availability of forms for oral administration is a direct consequence of the acid stability of the Flucloxacillin component, which prevents its rapid breakdown in the stomach. This stability allows the medicine to be delivered effectively via the Oral route. Both oral and parenteral formulations are available for therapeutic use. The inclusion of injectable forms ensures the drug can also be administered via the Parenteral route, such as Intramuscular or Intravenous injection, providing essential flexibility in clinical management.

What side effects are possible with Flustaph?

Possible Side Effects and Safety Information

The safety profile for Flustaph (Flucloxacillin) is defined by official regulatory documents that classify potential adverse reactions across various body systems. Reactions are grouped by frequency, from commonly observed events to very rare, serious concerns.

Adverse Reaction Classifications

Classification Organ System Focus Examples (as per regulatory documents)
Common Gastrointestinal Minor disturbances (e.g., nausea, mild diarrhea)
Uncommon Immune System / Skin Skin rash and urticaria (hives)
Very Rare Hepatobiliary, Immune System, Blood Hepatitis, cholestatic jaundice, anaphylactic shock, and severe blood disorders

The most clinically serious adverse reactions documented are severe Hepatobiliary Disorders (liver injury) and serious Immune System reactions like anaphylactic shock. Severe hepatic events, including hepatitis and jaundice, are classified as Very Rare and their onset may be delayed for up to two months following the completion of treatment. Serious cutaneous reactions like Stevens-Johnson syndrome (SJS) are also noted as Very Rare.

Population-Specific Safety Notes

Specific safety considerations exist for certain populations, as noted in official prescribing information. Older adults (aged 50 years and over) and individuals with a serious underlying disease are documented as having an increased risk of severe hepatic reactions. In newborns/neonates, caution is necessary due to the risk of hyperbilirubinaemia.

Flustaph is formally contraindicated in patients with a history of Flucloxacillin-associated jaundice or liver dysfunction, or a known hypersensitivity to any penicillin or other beta-lactam antibiotics.

Overdose and Emergency Response

The official regulatory profile for Flustaph (Flucloxacillin) overdose details both expected clinical manifestations and mandatory emergency actions, based strictly on government-authorized prescribing information.

Documented Overdose Presentations and Physiological Effects

Documented overdose presentations commonly include gastrointestinal effects such as nausea, vomiting, and diarrhoea, alongside minor gastrointestinal disturbances. More severe outcomes are specifically noted in regulatory labeling, primarily affecting the central nervous and metabolic systems. These include the risk of convulsions and neurological disorders, which are especially linked to high intravenous doses. Metabolic risks involve hypokalaemia and a risk of high anion gap metabolic acidosis in individuals with co-existing conditions such as severe renal impairment, sepsis, or malnutrition.

Emergency Response and Management

Regulatory authorities explicitly mandate that urgent medical attention must be sought immediately following any suspected overdose. This action is required even if there are no initial signs of discomfort or poisoning. Management is strictly supportive and symptomatic because no specific antidote is known for this substance. Procedural steps include continuous monitoring for clinical and laboratory signs of toxicity, with emphasis on potassium levels during high-dose exposure. The official guidance also notes that the substance is not significantly removed by dialysis.

Therapeutic Uses of Flustaph

Flustaph is commonly used to help with bacterial infections, with a distinct therapeutic scope centered on controlling infection and managing associated acute symptoms. The medication is applied across domains where additional symptomatic support is needed.

The therapeutic benefit is relevant for conditions characterized by periods of heightened symptoms, such as cellulitis, impetigo, deep infected wounds, and infections of the bone (osteomyelitis), the blood (septicaemia), or the heart lining. Flustaph is commonly used to support infectious disease management relevant to major surgery. The primary purpose is to help address symptom clusters that may become intense or disruptive, including symptoms related to physical discomfort and systemic imbalance.

This supportive assistance is relevant in contexts involving heightened systemic burden. As part of symptomatic management, it assists with maintaining functional stability, and contributes to improved comfort during symptomatic periods.

Quick Fact: Focus on Inflammatory Symptoms
Condition Focus Bacterial Infections (e.g., Staphylococcus)
Symptom Focus Symptoms related to inflammatory or irritative states
Core Benefit Provides support that helps ease the overall symptom burden
Context of Use Acute skin infections and surgical prophylaxis

Eligibility and Restrictions for Use

Who Can and Cannot Use Flustaph?

Eligibility for using Flustaph (Flucloxacillin) is strictly determined by official regulatory criteria, focusing on patient history and physiological status.

Absolute Contraindications

The medicine is prohibited for use in patients with a known history of hypersensitivity or severe allergy to penicillin or any other beta-lactam antibiotics.

It is also absolutely contraindicated in individuals with a previous history of jaundice or hepatic dysfunction specifically associated with prior flucloxacillin treatment.

Conditional Use and Restrictions

Population Group Regulatory Status
Severe Renal Impairment Conditional use; dose modification or extended dosing intervals must be considered.
Pre-existing Hepatic Dysfunction Use requires caution and close monitoring.
Newborns (Neonates) Not generally recommended; special caution is essential due to the risk of hyperbilirubinemia.
Older Adults (≥ 50 years) Use requires caution due to an increased risk of severe hepatic events.
Pregnancy and Lactation Use is conditional; only permitted when the physician determines that the potential benefits clearly outweigh the potential risks.

Eligibility is established for the general adult population and children above the neonatal period who do not present any contraindications.

What should I know about interactions with other medicines?

Flustaph (which contains flucloxacillin) can interact with a range of other medications, potentially altering the effect of either drug or increasing the risk of adverse reactions. It is important to inform your healthcare provider of all current medicines, supplements, and herbal remedies you are taking.

Medications Requiring Close Monitoring

  • Oral Anticoagulants (Blood Thinners): Concurrent use with medicines like warfarin may increase the effect of the anticoagulant, raising the risk of bleeding. Close monitoring of blood clotting time (INR) is generally required.
  • Methotrexate: Flustaph may increase the concentration of methotrexate in the body, potentially leading to increased toxicity, particularly in patients with kidney impairment. Monitoring for signs of toxicity (e.g., blood and gastrointestinal issues) is essential.
  • Probenecid: This medication, used for gout, can decrease the removal of flucloxacillin from the body, leading to higher and more prolonged levels of Flustaph in the blood. Your doctor may adjust the Flustaph dose.
  • Paracetamol (Acetaminophen): Long-term, heavy use of paracetamol with flucloxacillin may increase the risk of a rare but serious condition known as high anion gap metabolic acidosis (pyroglutamic acidosis).

Other Potential Interactions

  • Oral Contraceptives: Like many antibiotics, Flustaph may reduce the effectiveness of estrogen-containing oral contraceptives (birth control pills). An alternative non-hormonal method of contraception is recommended during treatment and for a short period afterward.
  • Typhoid Vaccine (Live, Oral): Flustaph may reduce the effectiveness of the live oral typhoid vaccine. Vaccination should be scheduled appropriately away from the antibiotic treatment course.

Mechanism of Action

How Flustaph Works: Mechanism of Action

Targeting the Bacterial Cell Wall Building Blocks

Flustaph exerts its effect by acting within the domain of bacterial cell wall biosynthesis. It specifically targets and irreversibly inhibits Penicillin-Binding Proteins (PBPs), which are the bacterial transpeptidases responsible for the final cross-linking step of the peptidoglycan structure. This targeted mechanism initiates a cascade that leads to the destabilization of the cell wall structure .


The Cascade of Osmotic Lysis

The drug engages a critical mechanistic cascade involving structural failure and subsequent osmotic instability. By arresting the creation of the rigid cell wall, Flustaph causes the bacterial cell to swell uncontrollably and rupture (lysis), a process described as a bactericidal effect. This key pathway disruption leads directly to the resulting physiological effect: a reduction in the overall viable bacterial load within the system.


High Selectivity for Bacterial Processes

Flustaph demonstrates high selectivity by acting solely on structures unique to bacteria, namely the peptidoglycan cell wall and its associated PBPs. This mechanism targets bacterial viability through structures that have no functional counterpart in human (eukaryotic) host cells. This focused mechanistic domain is essential as it facilitates the elimination of the pathogen via this selective action.

Dosage and Administration Information

Official Administration Guidelines

Flustaph (Flucloxacillin) is governed by specific instructions that dictate its use in clinical practice. The officially approved routes of administration include oral forms (capsules and suspension) and parenteral forms, primarily administered via Intravenous (IV) or Intramuscular (IM) injection, depending on the severity of the condition.

Dosing and Scheduling

The standard adult oral dose typically ranges from 250 mg to 500 mg per dose. Systemic administration is generally scheduled four times a day, aiming for consistent six-hourly intervals. For severe or deeply seated infections, doses may be increased to up to 1 g per administration, with the maximum recommended dose reaching 8 g to 12 g daily in specific circumstances. The regimen for surgical prophylaxis involves an initial 1 g to 2 g IV dose followed by a scheduled course that may last up to 72 hours.

Procedural Requirements

Oral administration is strictly required to be on an empty stomach, meaning at least 60 minutes before a meal or 2 hours after consuming food, to ensure optimal absorption. Capsules must be swallowed whole with a full glass of water, and it is advised to avoid lying down immediately after intake. Parenteral preparations require reconstitution with sterile water prior to injection, and the IV administration must be performed slowly over three to four minutes.

Population Adjustments

Dosage adjustments are mandated for adults with severe renal impairment (Creatinine Clearance < 10 mL/min), typically reducing the maximum dose to 1 g every 8 to 12 hours. If an oral dose is missed, it should be taken as soon as possible, ensuring a minimum of 4 hours before the next scheduled dose, and the dose must never be doubled.

Recent Clinical Evidence

Research Evidence / Overview of Studies for Flustaph

Evidence for Use in Acute Skin and Soft Tissue Infections

Research examined the use of Flustaph for common conditions like cellulitis and infected wounds. The research landscape here includes many Randomized Controlled Trials (RCTs), a type of study often used to evaluate medical treatments. These trials were conducted to examine outcomes related to physical discomfort and systemic imbalance. Studies monitored responses over defined time intervals.

Studies reported patterns observed in the measured change in clinical status measures among the populations studied. Research also documents measurements related to patient-reported outcomes, such as how pain and functional activity levels were recorded. Because different studies used different ways to define "treatment success" or "treatment failure," the evidence contributes to understanding symptom patterns but sometimes also describes heterogeneity (variability) in the reported findings.

Evidence for Use in Staphylococcus aureus Bloodstream Infection

Flustaph was studied for bloodstream infections (septicaemia), which are conditions involving periods of heightened symptoms and physiological strain. Research was conducted using Observational Cohort Studies and some Pilot RCTs that focus on critically ill patient populations. The studies explored outcomes related to mortality rates (e.g., at 30 and 90 days), the persistence of bacteria in blood samples, and the rate of hospital readmission related to the infection.

Data show patterns related to the observed mortality rates among the study groups. Research describes the frequency with which microbiological outcomes were recorded, such as when bacteria were no longer detected in the blood of observed populations.

Evidence for Use in Bone Infection (Osteomyelitis) and Surgical Prophylaxis

Research for bone infections is primarily composed of Retrospective Cohort Studies that observed patient records over extended periods to examine outcomes related to change in clinical status and the frequency of infection recurrence. For Surgical Prophylaxis, Flustaph was evaluated in Randomized Controlled Trials that monitored measurements of Surgical Site Infection (SSI) frequency in the post-operative period.

What Remains Uncertain and Gaps in the Evidence

Evidence highlights what is known and what is still uncertain about Flustaph. Evidence quality varies across studies, with many indications relying on strong RCTs, while others, like bone infection management, rely heavily on observational data. Comparative evidence is lacking in several areas, particularly for defining the optimal duration of therapy. Furthermore, data are still emerging, and certainty remains low regarding the best treatment approach in some complex situations.

Key Studies & References

  1. Summary of the evidence | Cellulitis and erysipelas: antimicrobial prescribing (NICE Guideline NG141)

Frequently Asked Questions (FAQ)

Common questions about Flustaph (FAQ)


Q: What is the main difference between Flustaph and similar medicines?

A: The medicine is classified as a penicillinase-resistant penicillin. This characteristic means it is designed to effectively counteract the penicillinase enzymes produced by certain defensive bacteria like staphylococci. This allows it to target bacteria that may be resistant to older penicillins.


Q: Does Flustaph make you sleepy or tired?

A: Regulatory side effect profiles state that general feelings of tiredness (malaise) and dizziness are possible side effects. Patients are generally advised to be aware if these effects occur. Specific concerns related to fatigue may be discussed with a healthcare professional.


Q: Is it normal to feel a change in appetite while taking Flustaph?

A: Official adverse reaction profiles list the possibility of absent appetite in some cases. This is in addition to common gastrointestinal disturbances like nausea and mild diarrhea. Significant or concerning changes are generally reviewed by a healthcare professional.


Q: Can Flustaph affect my ability to drive or operate machinery?

A: Official documents from some regulatory authorities state that adverse effects on the ability to drive or operate machinery have not been observed. Patients are generally advised to exercise caution if side effects like dizziness or fatigue are experienced.


Q: Are there any common foods or drinks that interact with Flustaph?

A: Official instructions require taking the medicine on an empty stomach (60 minutes before or 2 hours after food) to ensure proper absorption. While specific foods or drinks are not listed as forbidden, the strict scheduling is the key regulatory instruction regarding food intake.


Q: Is Flustaph suitable for children?

A: Official information states the medicine is generally considered for use in children above the neonatal period (newborn phase). Special caution is necessary for newborns due to the risk of hyperbilirubinemia, which is a condition involving high levels of bilirubin in the blood.


Q: What is the purpose of the different strengths of Flustaph?

A: Regulatory documents indicate that the different strengths (e.g., 250 mg to 1 g) are used based on the severity and location of the infection being treated. Higher strengths are often reserved for more severe or deeply seated infections.


Q: Is Flustaph only used for [main indication] or are there other conditions?

A: According to official documents, the medicine is used for more than one condition. These uses include acute skin and soft tissue infections, Staphylococcus aureus bloodstream infection, and bone infection (osteomyelitis).


Q: Are the research findings on Flustaph promising?

A: Research evidence describes patterns in clinical status measures and mortality rates observed in studies. Official documents also state that evidence quality varies and that comparative evidence for optimal treatment duration is still lacking, highlighting both known benefits and remaining uncertainties.


Q: Why does the official leaflet list so many possible side effects?

A: Regulatory bodies require that a comprehensive safety profile be included in all official patient materials. Adverse reactions are classified into frequency groups (Common, Uncommon, Very Rare) and listed across various body systems to provide complete transparency as required by law.


Q: What happens if I accidentally take more Flustaph than prescribed? (Informational, not advisory)

A: Official patient information describes symptoms of having taken more than prescribed, which may include feeling or being sick and diarrhea. Suspected excessive intake is typically reviewed by a healthcare professional.


Q: Does Flustaph interact with alcohol?

A: Official safety information indicates that patients can consume alcohol while undergoing treatment. Concerns about alcohol consumption may be discussed with a prescriber.


Q: Is Flustaph a narcotic or controlled substance?

A: The medicine is chemically classified as a Beta-lactam Antibiotic and a Penicillinase-Resistant Penicillin. It is not classified as a narcotic or controlled substance.


Q: Can Flustaph be crushed or cut in half?

A: Regulatory guidelines clearly state that capsules must be swallowed whole with a full glass of water. This is required for the medicine to be absorbed correctly. Official documents do not typically address modifying other forms, such as the oral suspension.


Q: If I feel better, can I just stop taking Flustaph?

A: Official patient information indicates that treatment is not typically stopped early. This is because some bacteria may survive, which could allow the infection to come back.


Q: Why is Flustaph sometimes prescribed at a lower starting dose?

A: Dosage adjustments are formally mandated for adults with severe renal impairment (a serious kidney condition). In these cases, the maximum dose is typically reduced to prevent the medicine from accumulating in the body.


Q: What should I know about Flustaph before a planned surgery?

A: The medicine is formally evaluated and used for surgical prophylaxis (preventing infection before surgery). Studies monitor outcomes related to the frequency of surgical site infection in the post-operative period. It is generally necessary to inform your surgical team if this medicine is being taken.


Q: Is Flustaph available as a generic medicine?

A: The medicine's active therapeutic component is Flucloxacillin, which is the internationally accepted generic name for the substance.


Q: What kind of monitoring is needed while taking Flustaph?

A: Official documents describe the need for close monitoring in certain circumstances. For example, monitoring of blood clotting time (INR) is required when taken with specific blood thinners. Monitoring of liver function is also necessary due to the risk of severe hepatic events.


Q: How often are people checked by a doctor when on Flustaph?

A: Official documents require specific monitoring, such as measuring potassium levels regularly during higher doses and close monitoring of blood clotting time (INR) when taken with certain other medicines. The frequency of general follow-up is typically addressed by a healthcare provider.


Q: What is the typical duration of treatment with Flustaph?

A: Official dosing information mentions use for surgical prophylaxis lasting up to 72 hours. For other types of infections, research notes that the optimal duration of therapy is an area where comparative evidence is still being studied.


Q: Does Flustaph affect sleep patterns?

A: Regulatory side effect profiles list the possibility of general feelings of tiredness (malaise) and dizziness. While this medicine is not listed for sleep disturbance, these effects could indirectly relate to changes in sleep patterns.


Q: What is meant by 'contraindication' for Flustaph?

A: A contraindication is a patient-friendly term for a specific condition or history (such as a known penicillin allergy) that prohibits the use of the medicine because the risks are known to outweigh the benefits. This classification describes conditions where the medicine is typically avoided, as defined in official documents.


Q: Can I take Flustaph if I have a history of heart issues?

A: A general history of heart issues is not listed as a contraindication. The medicine is used in some cases to treat serious infections like endocarditis (infection of the heart lining) and to prevent infection during some heart surgeries.

How should Flustaph be stored and disposed of?

Storage and Disposal of Flustaph

Proper storage is essential to maintain the stability of Flustaph (Flucloxacillin). Capsules must generally not be stored above 25 C, while the unreconstituted powder for oral solution is stored below 30 C and protected from light. The medicine must always be kept in its original package and stored out of the sight and reach of children.

Once the oral solution is mixed, it requires specific conditions: it must be stored in a refrigerator (2 C-8 C) and used within 7 days; it must not be frozen. Unused or expired Flustaph must not be disposed of in household waste or wastewater; discard the product according to local pharmaceutical waste regulations.

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

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