Dicloxacillin !

An oral penicillinase-resistant penicillin for skin and soft-tissue infections due to methicillin-susceptible Staphylococcus aureus.

Updated 2026-11-01

Class: Beta-lactams
Enzyme: Penicillin-binding proteins (bacterial transpeptidases)
ATC code: J01CF01

Penicillin-binding proteins (bacterial transpeptidases)Dicloxacillin

The figure shows oxacillin, an isoxazolyl penicillin of the same group, in Staphylococcus aureus PBP1; no structure of this drug bound to a PBP has been published.

Target in 3D: Penicillin-binding proteins (bacterial transpeptidases). PDB structure 8VBU (RCSB PDB, public domain). View the structure at RCSB PDB

Mechanism of action

Dicloxacillin is an oral isoxazolyl penicillin, stable in stomach acid. It belongs to the penicillins resistant to staphylococcal β-lactamase: its bulky side chain keeps penicillinase from opening the β-lactam ring, so it acylates the PBPs of penicillinase-producing staphylococci. It does not work against MRSA, whose PBP2a has low affinity for β-lactams.

Staphylococcal penicillinase cannot open its ring
Acylates the staphylococcal PBPs
Peptidoglycan cross-linking stops
The staphylococcus lyses

Pharmacokinetics

Absorption: Oral; better absorbed on an empty stomach.
Distribution: Very high protein binding, mainly to albumin; reaches bile and pleural and amniotic fluids.
Elimination: By the kidney and by liver inactivation and bile.
Half-life: Short, under one hour.

Indications

Skin and soft-tissue infections due to penicillinase-producing staphylococci. Cellulitis of the leg →
Staphylococcal osteomyelitis and septic arthritis. Osteomyelitis →

Adverse effects

Common

Nausea, vomiting, diarrhoea, epigastric pain
Rash

Contraindications

History of a hypersensitivity reaction to any penicillin

Key interactions

Warfarin and other coumarins: May reduce the anticoagulant effect; the INR is monitored.
Tetracyclines: Bacteriostatic: they can antagonise the bactericidal effect; the combination is avoided.

What is monitored

INR if the patient takes warfarin
Kidney and liver function and blood count in long courses

Administration and safety

Oral, one hour before or two hours after meals.
Do not confuse dicloxacillin with doxycycline or cloxacillin.

Nursing care

Before the first dose: ask about allergy to penicillins, cephalosporins and other β-lactams, and what the reaction was.
Explain that it is taken away from meals.
Check whether the patient takes warfarin.
Teach the patient to report watery or bloody diarrhoea, even weeks after the course ends.

Pregnancy and breastfeeding

Animal studies showed no fetal harm and there are no controlled studies in pregnant women; used if clearly needed.

Test yourself

Think of the answer, then tap the question to see it.

Against which staphylococci does dicloxacillin work, and against which not?

It works against methicillin-susceptible penicillinase producers; not against MRSA, which carries PBP2a.

Which anticoagulant interaction does its label describe?

It may reduce the response to warfarin; the INR is monitored.

When is dicloxacillin given relative to meals?

Away from them: one hour before or two hours after, because it is better absorbed fasting.

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Educational content on how drugs work; not a prescribing guide and no substitute for a health professional's advice. No doses are given.

Sources: Dicloxacillin: MedlinePlus Drug Information (MedlinePlus (U.S. National Library of Medicine), 2026); DailyMed - DICLOXACILLIN SODIUM capsule (DailyMed (U.S. National Library of Medicine), 2026); RCSB PDB - 8VBU: Structure of the monofunctional Staphylococcus aureus PBP1 in its beta-lactam (Oxacillin) inhibited form (RCSB Protein Data Bank, 2026); Farmacología básica y clínica (Katzung), cap. 43 (McGraw Hill, 2025).

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Representative model, for educational purposes only.