Fusidic acid, a steroidal antibiotic primarily used to treat bacterial infections caused by Gram-positive organisms such as Staphylococcusaureus, was discovered in the early 1960s and introduced into clinical use shortly thereafter. Its history is marked by its strong activity against staphylococcal infections, particularly skin and soft tissue infections, while also being widely used in topical formulations for dermatological conditions. Fusidic acid is included in various topical and systemic preparations in many countries and is often used in combination therapies depending on the infection severity. Its development included extensive microbiological screening from fungal sources and subsequent clinical evaluation that established its effectiveness and safety profile for antibacterial use.
BRAND NAMES
Fucidin – one of the most widely used global brands (topical cream, ointment, and oral forms in some regions)
Fucithalmic – ophthalmic (eye drop/gel) formulation used for eye infections
Fusibet – combination product (fusidic acid + corticosteroid, such as betamethasone) used in skin conditions.
MECHANISM OF ACTION
Fusidic acid is a bacteriostatic antibiotic (and bactericidal at high concentrations) that works by inhibiting bacterial protein synthesis. Its primary mechanism involves binding to elongation factor G (EF-G) on the bacterial ribosome. This prevents EF-G from facilitating the translocation step during protein elongation, effectively blocking the movement of the ribosome along messenger RNA (mRNA).
PHARMACOKINETICS
Absorption:
Fusidic acid is well absorbed after oral administration, although its absorption can vary depending on formulation and food intake. It is also commonly used in topical and ophthalmic preparations, where systemic absorption is minimal.
Distribution:
Fusidic acid has a small to moderate volume of distribution and is highly bound to plasma proteins (greater than 90%), mainly albumin.
Metabolism:
Fusidic acid is primarily metabolized in the liver, where it undergoes hepatic biotransformation (mainly via CYP-independent pathways) into inactive metabolites. It does not significantly induce or inhibit cytochrome P450 enzymes, reducing the risk of major metabolic drug interactions.
Elimination:
Fusidic acid is mainly eliminated through biliary excretion into feces, with only a small fraction excreted via the kidneys. Minimal unchanged drug is recovered in urine. Its elimination half-life is relatively long, contributing to sustained antibacterial effects, especially in systemic use.
PHARMACODYNAMICS
Fusidic acid is a steroidal antibiotic that is primarily effective against Gram-positive bacteria, especially Staphylococcus aureus. It works by inhibiting bacterial protein synthesis through binding to elongation factor G (EF-G) on the ribosome, preventing the translocation step required for peptide chain elongation.
ADMINISTRATION
Fusidic acid is administered in several formulations depending on the site and severity of infection. It is available as oral tablets or suspension for systemic infections, topical creams or ointments for skin and soft tissue infections, and ophthalmic preparations for bacterial eye infections.
DOSAGE AND STRENGTH
Fusidic acid dosing and strength vary depending on the formulation and indication. For oral use in adults, it is commonly prescribed at a dose of 250 mg two to three times daily, depending on the severity of infection and clinical response.
DRUG INTERACTIONS
Fusidic acid has relatively few but clinically important drug interactions. The most significant interaction occurs with statins, where concurrent use can increase the risk of myopathy and rhabdomyolysis, especially with systemic (oral or intravenous) administration.
FOOD INTERACTIONS
There are no major food interactions with fusidic acid. Oral absorption is generally not significantly affected by food intake.
CONTRAINDICATIONS
Fusidic acid is contraindicated in patients with known hypersensitivity to fusidic acid or any component of its formulations. It should also be avoided in individuals with severe hepatic impairment, particularly when systemic therapy is required, due to its hepatic metabolism and the risk of drug accumulation.
SIDE EFFECTS
Gastrointestinal upset (nausea, abdominal discomfort)
Skin rash or allergic reactions
Elevated liver enzymes (with systemic use)
Local irritation (topical or ophthalmic use)
OVER DOSAGE
Overdosage of fusidic acid is uncommon, but when it occurs—especially with systemic (oral or intravenous) use—it is generally associated with dose-related exaggeration of its known adverse effects rather than a unique toxic syndrome.
TOXICITY
Fusidic acid is generally well tolerated, but toxicity is more likely with systemic (oral or intravenous) use, especially at high doses or prolonged therapy. The most clinically important toxicity involves the liver and musculoskeletal system.
