Flucloxacillin is a narrow-spectrum β-lactam antibiotic belonging to the penicillinase-resistant penicillins, developed in the 1960s and introduced into clinical use to treat infections caused by penicillin-resistant Staphylococcus species. Its history is marked by its effectiveness in managing skin and soft tissue infections, bone infections, and other staphylococcal diseases, while maintaining stability against bacterial β-lactamase enzymes. Flucloxacillin became widely used in clinical practice due to its improved resistance profile compared to earlier penicillins and is included in standard treatment regimens for staphylococcal infections in many countries. It has remained an important antibiotic in outpatient and hospital settings, particularly for infections where methicillin-sensitive Staphylococcus aureus (MSSA) is suspected or confirmed.
BRAND NAMES
Floxapen (one of the most widely known brands)
Flopen
Staphylex
Fluclox
MECHANISM OF ACTION
Flucloxacillin is a beta-lactam antibiotic that works by inhibiting bacterial cell wall synthesis. It binds to penicillin-binding proteins (PBPs) and blocks the transpeptidation step of peptidoglycan formation. This weakens the bacterial cell wall, leading to cell lysis and death, making it bactericidal, especially against penicillinase-producing Staphylococcus aureus.
PHARMACOKINETICS
Absorption
Flucloxacillin is moderately absorbed after oral administration, but absorption is reduced by food. Peak plasma concentrations are usually reached within 1–2 hours.
Distribution
It is widely distributed in body tissues, with moderate plasma protein binding (~95%). It penetrates well into bones, joints, and soft tissues, but has limited penetration into cerebrospinal fluid.
Metabolism
Flucloxacillin undergoes minimal hepatic metabolism. Most of the drug remains unchanged in the body.
Elimination
It is primarily eliminated by the kidneys through tubular secretion, with a short half-life of about 0.75–1 hour in healthy individuals. Dose adjustment may be needed in renal impairment.
PHARMACODYNAMICS
Flucloxacillin acts by inhibiting bacterial cell wall synthesis in actively dividing bacteria. It is particularly effective against β-lactamase-producing staphylococci, making it useful in treating skin, soft tissue, bone, and respiratory tract infections caused by susceptible organisms.
ADMINISTRATION
Flucloxacillin is administered orally in capsule or liquid form, and also intravenously in hospital settings for severe infections. It is best taken on an empty stomach for optimal absorption. The dosing schedule depends on the severity and type of infection.
DOSAGE AND STRENGTH
Dosage varies based on infection severity and patient age. It is typically given multiple times daily due to its short half-life. Higher intravenous doses are used in severe systemic infections.
DRUG INTERACTIONS
Flucloxacillin may reduce the effectiveness of oral anticoagulants like warfarin by altering gut flora. It may also have interactions with other antibiotics or drugs affecting renal function.
FOOD INTERACTIONS
Food reduces the absorption of flucloxacillin; therefore, it is usually recommended to take it on an empty stomach (1 hour before or 2 hours after meals).
CONTRAINDICATIONS
Flucloxacillin is contraindicated in patients with known hypersensitivity to penicillins or other beta-lactam antibiotics. Caution is needed in patients with a history of severe allergic reactions.
SIDE EFFECTS
Nausea and vomiting
Diarrhea
Skin rash
Allergic reactions (including anaphylaxis in rare cases)
Elevated liver enzymes (rare)
OVER DOSAGE
Overdose of flucloxacillin is uncommon but may occur due to excessive dosing or accumulation in patients with impaired kidney function. The main effects involve the gastrointestinal system, kidneys, and nervous system. Symptoms may include nausea, vomiting, diarrhea, abdominal discomfort, and electrolyte imbalance.
TOXICITY
Overdose of Flucloxacillin may cause gastrointestinal disturbances, electrolyte imbalance, and in severe cases, neurotoxicity such as seizures (especially in renal impairment). Management is mainly supportive, including discontinuation of the drug, hydration, and symptomatic treatment. Hemodialysis may help in severe toxicity cases.
