Flucloxacillin

1. Introduction

Flucloxacillin is a beta-lactam penicillin antibiotic primarily used to treat infections caused by penicillinase-producing staphylococci and other susceptible bacteria. It works by inhibiting bacterial cell wall synthesis, leading to bacterial death. It is commonly used for skin, soft tissue, and bone infections.

2. Indications

  • Approved Indications:
    • Skin and soft tissue infections (e.g., cellulitis, impetigo, abscesses).
    • Bone and joint infections (e.g., osteomyelitis).
    • Respiratory tract infections (e.g., pneumonia, bronchitis).
    • Endocarditis.
    • Prophylaxis in surgical procedures to prevent staphylococcal infections.
  • Off-Label Uses:
    • Management of mastitis in lactating women.

3. Dosage

  • Adults:
    • Mild to moderate infections: 250–500 mg every 6 hours.
    • Severe infections: Up to 1 g every 6 hours.
    • Endocarditis or osteomyelitis: 2 g every 6 hours, administered intravenously.
  • Children:
    • Oral: 12.5–25 mg/kg every 6 hours (maximum: 1 g per dose).
    • Intravenous: 25–50 mg/kg every 6 hours (maximum: 2 g per dose).
  • Neonates:
    • 25–50 mg/kg every 12 hours in the first week of life, then every 8 hours thereafter.

4. Administration

  • Oral: Take on an empty stomach, 1 hour before or 2 hours after meals, with water.
  • Intravenous: Administer as per hospital protocol.
  • Intramuscular: Used for certain severe infections when IV access is unavailable.

5. Forms Available

  • Capsules: 250 mg, 500 mg.
  • Oral suspension: 125 mg/5 mL, 250 mg/5 mL.
  • Powder for injection: 250 mg, 500 mg, 1 g, 2 g vials.

6. Side Effects

6.1. Common Side Effects

  • Nausea.
  • Diarrhoea.
  • Abdominal discomfort.

6.2. Less Common Side Effects

  • Rash.
  • Vomiting.
  • Sore mouth or tongue.

6.3. Rare but Serious Side Effects

  • Hepatotoxicity (e.g., cholestatic jaundice, hepatitis).
  • Severe allergic reactions (e.g., anaphylaxis).
  • Clostridioides difficile-associated diarrhoea (CDAD).

7. Warnings

  • Allergic Reactions: Avoid in patients with a history of penicillin hypersensitivity.
  • Hepatic Impairment: Risk of cholestatic jaundice, particularly with prolonged use.
  • Clostridioides difficile Infection: Monitor for persistent or severe diarrhoea.

8. Precautions

  • Use cautiously in patients with renal or hepatic impairment; dose adjustments may be necessary.
  • Monitor for signs of superinfection during prolonged use.

9. Interactions

  • Drug-Drug Interactions:
    • Methotrexate: Increased methotrexate toxicity due to reduced renal clearance.
    • Oral contraceptives: Reduced efficacy; consider additional contraceptive measures.
    • Probenecid: Increases plasma concentration of flucloxacillin by reducing renal excretion.
  • Drug-Food Interactions:
    • Food reduces absorption; take on an empty stomach.

10. Monitoring Parameters

  • Symptom improvement (e.g., resolution of fever, infection signs).
  • Liver function tests during prolonged therapy.
  • Monitor for hypersensitivity reactions, especially after the first dose.

11. Use in Children

  • Safe and commonly used in paediatric populations, with doses adjusted according to weight.

12. Use in Pregnancy

  • Category B: Generally considered safe in pregnancy, but use only when clearly needed.

13. Use in Elderly

  • Safe for elderly patients, but monitor renal and hepatic function closely.

14. Use in Kidney Disease

  • Dose adjustments are required in severe renal impairment:
    • Creatinine clearance <10 mL/min: Administer every 12 hours.

15. Use in Liver Disease

  • Use with caution due to the risk of cholestatic jaundice and hepatitis, particularly in prolonged therapy.

16. Patient Counselling Points

  • Take flucloxacillin on an empty stomach for optimal absorption.
  • Complete the full course, even if symptoms improve early.
  • Inform your doctor if you experience severe diarrhoea, yellowing of the skin or eyes, or signs of an allergic reaction (e.g., rash, swelling).
  • Store oral suspension in the refrigerator and shake well before use.
  • Avoid alcohol to reduce strain on the liver during therapy.

17. Table of Brand Names, Manufacturers, and Prices

Brand NameManufacturerPrice (USD)
FloxapenGlaxoSmithKline$15–25 (30 capsules, 500 mg)
StaphylexAspen$10–20 (30 capsules, 500 mg)
Generic FlucloxacillinVarious$5–15 (30 capsules, 500 mg)

18. FAQs (15 Questions)

  1. What is flucloxacillin used for?
    It is used to treat bacterial infections such as cellulitis, impetigo, and pneumonia.
  2. How does flucloxacillin work?
    It inhibits bacterial cell wall synthesis, leading to the destruction of bacteria.
  3. How long does flucloxacillin take to work?
    Symptom improvement may occur within 48–72 hours, but the full course should be completed.
  4. What are the common side effects of flucloxacillin?
    Common side effects include nausea, diarrhoea, and abdominal discomfort.
  5. Can flucloxacillin cause liver problems?
    Yes, it may cause cholestatic jaundice or hepatitis, particularly with prolonged use.
  6. Can I take flucloxacillin with food?
    No, take it on an empty stomach to ensure optimal absorption.
  7. Is flucloxacillin safe during pregnancy?
    Yes, it is generally considered safe during pregnancy.
  8. Does flucloxacillin interact with other medications?
    Yes, it interacts with methotrexate, oral contraceptives, and probenecid.
  9. What should I do if I miss a dose of flucloxacillin?
    Take it as soon as you remember, but skip it if it’s close to the next dose. Do not double up.
  10. Can flucloxacillin treat viral infections?
    No, flucloxacillin is effective only against bacterial infections.
  11. How should flucloxacillin oral suspension be stored?
    Store in the refrigerator and use within 7–14 days of preparation.
  12. Can flucloxacillin cause allergic reactions?
    Yes, allergic reactions such as rash, itching, or anaphylaxis may occur.
  13. How long is a typical course of flucloxacillin?
    Treatment usually lasts 7–14 days, depending on the severity of the infection.
  14. Can children take flucloxacillin?
    Yes, it is safe and commonly used in children with appropriate dose adjustments.
  15. How should flucloxacillin be stored?
    Store capsules and tablets at room temperature, away from moisture and heat.