Action and Spectrum

Actions and Spectrum: 

flucloxacillin is a narrow-spectrum antibiotic that typically belongs to the penicillin class of antibiotics. It is used to treat bacterial infections which is caused by susceptible organisms. Here’s an overview of its action and spectrum: 

Action:  

flucloxacillin works by inhibiting the synthesis of bacterial cell walls. It specifically targets and binds to a penicillin-binding protein (PBP) called transpeptidase, which is involved in cross-linking peptidoglycan chains in the bacterial cell wall. By inhibiting this process, flucloxacillin weakens and disrupts the integrity of the cell wall, leading to cell lysis and death of the bacteria. 

Spectrum:  

flucloxacillin has a narrow spectrum of activity and is primarily effective against certain gram-positive bacteria, particularly those that produce the enzyme beta-lactamase. Beta-lactamase is an enzyme that breaks down penicillin, making bacteria resistant to many penicillin antibiotics. 

Drug Interaction

Adverse Reaction

Frequency not defined 

CNS toxicity 

Erythematous rash 

Angioedema 

Gastro-intestinal disturbances 

Convulsions 

Neutropenia 

Cholestatic jaundice 

Rash 

Paraesthesia 

Hemolytic anemia 

Stevens-Johnson syndrome 

Vomiting 

Thrombocytopenia 

Arthralgia 

Hypersensitivity reactions 

Serum sickness-like reactions 

Nausea 

Joint pain 

Coagulation disorders 

Diarrhea 

Agranulocytosis 

Erythema multiforme 

Myalgia 

Fever 

Black tongue 

Impaired platelet function 

Hepatitis 

Prolonged bleeding 

Urticaria 

Sore mouth 

Anaphylaxis 

Toxic epidermal necrolysis 

Black Box Warning

Black Box Warning: 

None 

Contraindication / Caution

Contraindication/Caution: 

Contraindication 

• Hypersensitivity or Allergy: flucloxacillin is a penicillin antibiotic, and individuals with known hypersensitivity or allergy to penicillin or other beta-lactam antibiotics should not take flucloxacillin. Allergic reactions to penicillin can range from mild skin rashes to severe, life-threatening reactions like anaphylaxis. 
• Previous Severe Skin Reactions: Individuals who have experienced severe skin reactions, like Stevens-Johnson syndrome, toxic epidermal necrolysis/drug reactions with eosinophilia and systemic symptoms (DRESS), associated with flucloxacillin or any other penicillin antibiotic should avoid using flucloxacillin. 
• Infectious Mononucleosis: flucloxacillin is generally contraindicated in individuals with infectious mononucleosis (also known as glandular fever or mono) due to the increased risk of developing a skin rash. 
• Liver Dysfunction: flucloxacillin is primarily eliminated from the body through the liver. Individuals with severe liver dysfunction or a history of liver disease should exercise caution when using flucloxacillin, as the medication may further impair liver function. 
• Renal Dysfunction: While flucloxacillin is primarily eliminated through the liver, it is also partially excreted by the kidneys. Individuals with severe renal dysfunction or impaired kidney function should be closely monitored when using flucloxacillin, as dosage adjustments may be necessary. 
• Methicillin-Resistant Staphylococcus aureus (MRSA) Infections: flucloxacillin is ineffective against MRSA, a type of bacteria resistant to many antibiotics, including flucloxacillin. Therefore, it should not be used to treat MRSA infections. 

Caution 

• Allergic Reactions: Although rare, allergic reactions to flucloxacillin can occur. It’s essential to monitor for signs of allergic reactions, such as rash, itching, swelling, difficulty breathing, or severe dizziness. If any of these symptoms occur, medical attention should be sought immediately. 
• Clostridium difficile-associated Diarrhea: Antibiotic use, including flucloxacillin, can interrupt the average balance of bacteria in the intestines and lead to the overgrowth of a bacterium called Clostridium difficile. This can result in severe Clostridium difficile-associated diarrhea (CDAD). If persistent, watery, or bloody diarrhea occurs during or after treatment with flucloxacillin, it is crucial to contact a healthcare professional. 
• Interactions with Other Medications: flucloxacillin may interact with other medications, including oral contraceptives (birth control pills). It can reduce the effectiveness of hormonal contraceptives and increase the risk of unintended pregnancy. Alternative or additional contraceptive methods should be considered while taking flucloxacillin and after discontinuing the medication. Discussing potential interactions with other medications with a healthcare professional is important. 
• Renal Impairment: flucloxacillin is eliminated from the body, in part, through the kidneys. In individuals with impaired renal function, dosage adjustments might be necessary to prevent drug accumulation and potential toxicity. Close monitoring of kidney function and adjustment of the dosage as needed is essential in such cases. 
• Liver Impairment: flucloxacillin is primarily metabolized in the liver. Individuals with pre-existing liver disease or impaired liver function may require dosage adjustments or careful monitoring while using flucloxacillin. 
• Superinfection: Antibiotic use, including flucloxacillin, can lead to the development of superinfections caused by resistant organisms. If new infections occur during treatment, appropriate measures should be taken. 

Pregnancy / Lactation

Pregnancy consideration:  

US FDA pregnancy category: Not assigned. 

Lactation:   

Excreted into human milk: Yes (Trace amounts). 

Pregnancy category: 

• Category A: well-controlled and Satisfactory studies show no risk to the fetus in the first or later trimester. 
• Category B: there was no evidence of risk to the fetus in animal studies, and there were not enough studies on pregnant women. 
• Category C: there was evidence of risk of adverse effects in animal reproduction studies, and no adequate evidence in human studies must take care of potential risks in pregnant women.    
• Category D: adequate data with sufficient evidence of human fetal risk from various platforms, but despite the potential risk, and used only in emergency cases for potential benefits.    
• Category X: Drugs listed in this category outweigh the risks over benefits. Hence these categories of drugs need to be avoided by pregnant women.    
• Category N: There is no data available for the drug under this category 

Pharmacology

Pharmacology: 

flucloxacillin is a narrow-spectrum antibiotic belonging to the penicillin class. It exhibits the bactericidal activity by inhibiting bacterial cell wall synthesis. Specifically, flucloxacillin binds to penicillin-binding proteins (PBPs) on the bacterial cell membrane, particularly transpeptidases, thereby interfering with the cross-linking of peptidoglycan chains in the cell wall. This disruption weakens the cell wall integrity, leading to cell lysis and bacterial death.

flucloxacillin is primarily effective against certain gram-positive bacteria, including methicillin-sensitive Staphylococcus aureus (MSSA) and Streptococcus pyogenes. It is not active against gram-negative bacteria or methicillin-resistant Staphylococcus aureus (MRSA). flucloxacillin is administered orally and eliminated mainly through hepatic metabolism and, to a lesser extent, renal excretion. 

Pharmacodynamics: 

Mechanism of action: The action of flucloxacillin involves its ability to inhibit the bacterial cell wall synthesis. flucloxacillin is a beta-lactam antibiotic and belongs to the penicillin class. 

• Inhibition of Penicillin-Binding Proteins (PBPs): flucloxacillin binds to and inhibits specific proteins known as penicillin-binding proteins (PBPs) on the bacterial cell membrane. PBPs play a crucial role in cross-linking peptidoglycan chains in the bacterial cell wall, providing structural integrity. 
• Disruption of Cell Wall Synthesis: By binding to PBPs, flucloxacillin interferes with the transpeptidation process, which involves the formation of cross-links between the peptidoglycan chains. This disruption weakens the bacterial cell wall and impairs its ability to withstand osmotic pressure. 
• Activation of Autolytic Enzymes: flucloxacillin also activates bacterial autolytic enzymes known as autolysins or murein hydrolases. Autolysins break down the existing peptidoglycan structure in the bacterial cell wall, leading to the cell lysis and death. 

By inhibiting cell wall synthesis and inducing cell lysis, flucloxacillin effectively targets and kills susceptible bacteria. It primarily acts against gram-positive bacteria, including Staphylococcus aureus (methicillin-sensitive strains) and Streptococcus pyogenes (Group A Streptococcus). It is important to note that flucloxacillin is ineffective against gram-negative bacteria or methicillin-resistant Staphylococcus aureus (MRSA). 

Pharmacokinetics: 

Absorption 

flucloxacillin is well-absorbed from the gastrointestinal tract after oral administration. The absorption occurs primarily in the small intestine. Food intake may affect the absorption rate but not the overall extent of absorption. 

Distribution 

flucloxacillin is distributed widely throughout the body tissues and fluids, including the skin, soft tissues, respiratory tract, and bones. 

Metabolism 

flucloxacillin undergoes minimal metabolism in the body. The majority of the drug remains unchanged and retains its antibacterial activity. There are no primary active metabolites formed during the metabolism of flucloxacillin. 

Elimination and Excretion 

flucloxacillin is primarily eliminated from the body through hepatic metabolism and biliary excretion. Only a tiny portion of the drug is excreted unchanged in the urine. 

Adminstartion

Administration: 

flucloxacillin is available in various formulations, including capsules, tablets, and oral suspensions. The specific administration instructions may vary depending on the formulation and the specific product.  

• Dosage: The flucloxacillin dosage will be based on the condition being treated, the severity of the infection, and the individual’s age, weight, and renal function. The prescribed dosage should be followed precisely as instructed by the healthcare professional. 
• Timing: flucloxacillin is usually taken orally, and taking it on an empty stomach is commonly recommended. However, the instructions may vary depending on the formulation and the product. It’s essential to follow the instructions the healthcare professional provides or the medication’s packaging. 
• Swallowing: If taking flucloxacillin in capsule or tablet form, swallow it whole with a glass of water. Do not crush, chew/break the capsules or tablets unless specifically instructed by the healthcare professional. 
• Suspension Preparation: If using the oral suspension form of flucloxacillin, shake the bottle well before use to ensure proper medication mixing. Use the provided measuring device or syringe to measure the correct dose as instructed. Depending on the specific product, the suspension may need to be reconstituted with water before use. Follow the instructions carefully for suspension preparation if required. 

Patient Information Leaflet

Patient information leaflet 

Generic Name: flucloxacillin 

Why do we use flucloxacillin? 

flucloxacillin is a penicillin-class antibiotic primarily used to treat bacterial infections caused by susceptible organisms.  

• Skin and Soft Tissue Infections: flucloxacillin is commonly used to treat various types of skin and soft tissue infections caused by susceptible bacteria, such as cellulitis, impetigo, boils, abscesses, and infected wounds. 
• Respiratory Tract Infections: flucloxacillin may treat respiratory tract infections caused by susceptible bacteria, including pharyngitis (strep throat), tonsillitis, sinusitis, and community-acquired pneumonia. 
• Bone and Joint Infections: flucloxacillin is sometimes used to treat bone and joint infections, such as osteomyelitis (infection of the bone) and septic arthritis (joint infection). 
• Endocarditis Prophylaxis: In some instances, flucloxacillin may be prescribed as prophylaxis to prevent bacterial endocarditis in individuals at high risk, such as those with certain heart conditions, undergoing dental or surgical procedures.