Fusidic Acid Cream 2%

What Is Fusidic Acid and What Is It Used For?

Quick Answer: Fusidic acid is a topical antibiotic cream that treats bacterial skin infections by stopping bacterial protein synthesis. It is primarily effective against Staphylococcus aureus and is used for conditions such as impetigo, infected eczema, and infected wounds.

Fusidic acid belongs to a unique and pharmacologically distinct group of antibiotics known as the fusidanes, originally isolated from the fermentation broth of the fungus Fusidium coccineum (now reclassified as Acremonium fusidioides). Unlike penicillins, macrolides, and other common antibiotic classes, fusidic acid occupies a unique niche in antimicrobial therapy. It inhibits bacterial protein synthesis by targeting elongation factor G (EF-G) on the bacterial ribosome, preventing the translocation step that is essential for protein chain elongation.

Specifically, fusidic acid stabilises the ribosome-EF-G-GDP complex after GTP hydrolysis has occurred, trapping the ribosome in a post-translocational state and preventing further rounds of protein synthesis. Recent research has also demonstrated that fusidic acid blocks ribosome recycling — the disassembly of ribosomes after translation termination — at concentrations approximately 1,000-fold lower than those required to inhibit translocation. This dual mechanism contributes to its bacteriostatic and, at higher concentrations, bactericidal activity. Because this mechanism is entirely distinct from other antibiotic classes, there is no cross-resistance between fusidic acid and beta-lactams, aminoglycosides, macrolides, tetracyclines, or quinolones.

Fusidic acid has a narrow spectrum of activity, primarily effective against gram-positive organisms. Its main clinical target is Staphylococcus aureus, against which it achieves minimum inhibitory concentrations (MIC) of 0.03–0.12 mcg/mL. Importantly, fusidic acid retains activity against many methicillin-resistant S. aureus (MRSA) strains because its mechanism targets EF-G rather than penicillin-binding proteins. It is also effective against coagulase-negative staphylococci, certain Streptococcus species, Corynebacterium minutissimum, and some Clostridium species. However, most gram-negative bacteria, including Enterobacteriaceae and Pseudomonas species, are inherently resistant.

Clinical Indications

Fusidic acid 2% cream is indicated for the treatment of mild to moderately severe, non-extensive, superficial primary and secondary skin infections caused by susceptible organisms. The principal indications include:

• Impetigo contagiosa — A highly contagious superficial bacterial skin infection primarily caused by S. aureus or Streptococcus pyogenes. Fusidic acid cream is a first-line topical treatment for localised, non-bullous impetigo with limited lesions (typically fewer than 3–5 lesions), with efficacy comparable to mupirocin.
• Infected eczema and atopic dermatitis — Secondary bacterial infection is a common complication of eczema, with S. aureus colonising lesional skin in over 90% of atopic dermatitis patients. Fusidic acid can be used alone or combined with topical corticosteroids.
• Infected wounds and abrasions — Traumatic wounds, surgical wounds, and minor cuts with secondary bacterial infection respond to topical fusidic acid when the causative organism is susceptible.
• Superficial folliculitis — Infection of hair follicles caused by staphylococci.
• Sycosis barbae — Staphylococcal infection of the beard area.
• Paronychia — Bacterial infection of the nail fold.
• Erythrasma — Superficial skin infection caused by Corynebacterium minutissimum.

What Should You Know Before Using Fusidic Acid?

Quick Answer: Do not use fusidic acid if you are allergic to the active substance or any of its excipients. Treatment should generally not exceed 14 days to reduce the risk of antibiotic resistance. It is considered safe during pregnancy and breastfeeding due to negligible systemic absorption from topical application.

Contraindications

The only absolute contraindication to fusidic acid cream is hypersensitivity to fusidic acid (or sodium fusidate) or to any of the excipients in the formulation. The cream contains several excipients with known potential for causing local skin reactions, including butylhydroxyanisole (E320), cetyl alcohol, and potassium sorbate (E202). Patients with a documented history of allergic contact dermatitis to any of these substances should not use the product.

Warnings and Precautions

Antibiotic resistance is the most clinically significant concern with topical fusidic acid use. Bacterial resistance among S. aureus has been well documented and is increasing in many geographic regions. Extended or recurrent use significantly increases the risk of selecting for resistant organisms. Treatment courses should generally not exceed 7–14 days without clinical reassessment. The UK National Institute for Health and Care Excellence (NICE) and international antimicrobial stewardship guidelines recommend limiting topical fusidic acid use and reserving it for confirmed or strongly suspected staphylococcal infections.

Contact sensitisation may develop with prolonged or recurrent use. If signs of allergic contact dermatitis develop at the application site — including worsening redness, itching, swelling, or new vesicles — the product should be discontinued and an alternative treatment considered.

Eye contact should be avoided when applying fusidic acid cream to facial areas. The cream formulation contains excipients that can cause conjunctival irritation, stinging, and prickling sensations. If accidental eye contact occurs, the eyes should be flushed thoroughly with clean water.

Pregnancy and Breastfeeding

No adverse effects during pregnancy are anticipated, since systemic exposure to topically applied fusidic acid is negligible. Multiple published reports on the use of topical fusidic acid during pregnancy show no adverse effects on pregnancy outcomes or foetal development. The European Medicines Agency (EMA) product information states that fusidic acid cream may be used during pregnancy when clinically indicated. However, as with all medications, it should only be used after a healthcare provider has weighed the benefit-risk ratio.

Topical fusidic acid is compatible with breastfeeding. Systemic absorption from topical application is negligible, making it very unlikely that clinically significant amounts will pass into breast milk. The Drugs and Lactation Database (LactMed) classifies topical fusidic acid as compatible with breastfeeding. However, it is recommended to avoid applying the cream directly on the breast to prevent the infant from ingesting the cream during feeding. If application to the breast area is necessary, the area should be thoroughly cleaned before nursing.

No effects on fertility are anticipated due to the negligible systemic exposure from topical application. Fusidic acid cream can be used in children of all ages, including infants and neonates, with the same dosing regimen as adults. Clinical trials in paediatric impetigo have confirmed both efficacy and safety in the paediatric population, with comparable adverse effect profiles to adults.

How Does Fusidic Acid Interact with Other Drugs?

Quick Answer: Due to negligible systemic absorption from topical application, clinically significant pharmacokinetic drug interactions are not expected. However, caution is advised when applying multiple topical products to the same skin area, as absorption characteristics may be altered.

No formal interaction studies have been performed for topical fusidic acid cream. The negligible systemic absorption from cutaneous application means that the risk of pharmacokinetic interactions with systemically administered drugs is extremely low. However, there are several topical interaction considerations that patients and prescribers should be aware of.

Corticosteroid Combination Products

Fusidic acid is frequently combined with topical corticosteroids in licensed formulations for the treatment of infected inflammatory skin conditions. These include fusidic acid 2% with hydrocortisone acetate 1% for mild to moderate infected eczema, and fusidic acid 2% with betamethasone valerate 0.1% for more severe infected inflammatory dermatoses. These combinations are well studied and considered safe for short-term use (typically up to 2 weeks). The corticosteroid component addresses inflammation while fusidic acid treats the bacterial infection.

Important Note on Systemic Fusidic Acid

Although not relevant for the topical cream formulation, it is important to note that systemically administered fusidic acid (oral or intravenous) has significant drug interactions, particularly with statins (HMG-CoA reductase inhibitors). Concomitant systemic use of fusidic acid and statins can cause rhabdomyolysis, a potentially life-threatening breakdown of muscle tissue. This interaction is not clinically relevant for the topical cream due to negligible systemic absorption, but patients taking oral fusidic acid tablets should be advised to temporarily discontinue statin therapy.

What Is the Correct Dosage of Fusidic Acid?

Quick Answer: Apply a thin layer of fusidic acid 2% cream to the affected area 3–4 times daily for uncovered lesions. Under dressings, 1–2 times daily may be sufficient. Standard treatment duration is 7–10 days, with a maximum of 14 days without reassessment.

Adults

Children

Elderly

How to Apply

For optimal therapeutic effect, follow these application steps:

1. Wash and dry the affected area before application (unless clinically inappropriate, e.g., for weeping lesions).
2. Apply a thin layer of cream to the infected skin area.
3. Rub in gently until absorbed.
4. Wash your hands thoroughly after application (unless the hands are the treatment area).
5. If applying to the face, take special care to avoid the eyes.
6. If using a dressing, apply the cream before covering the area.

Missed Dose

If you forget to apply the cream at the scheduled time, apply it as soon as you remember and then continue with your usual schedule. Do not apply a double amount to compensate for a missed application. If it is almost time for your next application, skip the missed dose and continue as normal.

Overdose

Topical overdose with fusidic acid cream is unlikely to cause systemic effects or harm due to the negligible systemic absorption from cutaneous application. A standard 30 g tube contains a total of 600 mg of fusidic acid. If the cream is accidentally ingested, symptomatic and supportive treatment should be provided. Contact your local poison control centre or emergency department if a large amount has been swallowed, especially by a child.

What Are the Side Effects of Fusidic Acid?

Quick Answer: Fusidic acid cream is generally very well tolerated, with an overall adverse reaction rate of approximately 2.3% based on pooled clinical data from over 4,700 patients. Side effects are mostly mild and localised, including skin irritation, rash, and itching at the application site.

Like all medicines, fusidic acid cream can cause side effects, although not everybody gets them. The overall incidence of adverse reactions is low. Based on pooled data from clinical studies involving over 4,700 patients, the most commonly reported side effects are local skin reactions at the site of application. Serious adverse reactions, including systemic allergic reactions, are extremely rare.

Excipient-Related Reactions

The cream formulation contains several excipients that can independently cause local skin reactions in sensitised individuals. Butylhydroxyanisole (E320) may cause local contact dermatitis and can irritate eyes and mucous membranes. Cetyl alcohol may cause local skin reactions. Potassium sorbate (E202) may also cause contact dermatitis. These excipient-related reactions may be difficult to distinguish from drug-related adverse effects, and should be considered if a patient develops a reaction that does not resolve after discontinuing fusidic acid.

How Should You Store Fusidic Acid?

Quick Answer: Store fusidic acid cream below 25°C in its original packaging. After opening, use within 28 days. Keep out of the reach and sight of children. Do not refrigerate or freeze.

Proper storage of fusidic acid cream ensures that the medication remains effective and safe to use throughout its shelf life. Incorrect storage conditions can lead to degradation of the active ingredient and changes in the cream's consistency and effectiveness.

• Temperature: Do not store above 25°C. Keep the tube tightly closed when not in use.
• After first opening: Use within 28 days (4 weeks). It is recommended to write the date of first opening on the tube or carton.
• Shelf life (unopened): 2–3 years depending on the manufacturer. Check the expiry date printed on the packaging.
• Light protection: Store in the original packaging to protect from light.
• Temperature extremes: Do not refrigerate or freeze, as this may alter the consistency and effectiveness of the cream.
• Children: Keep out of the sight and reach of children.
• Disposal: Do not dispose of medicines via household waste or wastewater. Return unused or expired medication to your local pharmacy for proper disposal.

The cream is supplied in aluminium tubes with HDPE (high-density polyethylene) screw caps, available in 15 g and 30 g pack sizes. The cream itself is white to off-white with a smooth consistency. Do not use the cream if it has changed colour, developed an unusual smell, or if the tube appears damaged.

What Does Fusidic Acid Cream Contain?

Quick Answer: Each gram of cream contains 20 mg of fusidic acid (2%) as the active ingredient, in an oil-in-water emulsion base. The excipients include cetyl alcohol, glycerol, liquid paraffin, white soft paraffin, polysorbate 60, potassium sorbate, butylhydroxyanisole, and purified water.

Understanding the full composition of fusidic acid cream is important for identifying potential allergens and understanding how the formulation works. The cream is an oil-in-water emulsion, which makes it suitable for application to moist or weeping skin lesions. This contrasts with the ointment formulation (containing sodium fusidate rather than fusidic acid free base), which uses a lanolin and paraffin base more suited to dry, scaly lesions.

Three excipients in this formulation have known effects requiring specific warnings: butylhydroxyanisole (may cause contact dermatitis and eye/mucous membrane irritation), cetyl alcohol (may cause local skin reactions), and potassium sorbate (may cause contact dermatitis). Patients who are aware of sensitivities to any of these substances should inform their healthcare provider before starting treatment.