chemistry

Fusidic acid

Fusidic acid is a chemistry topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Fusidic acid rather than just read about it. In short: Fusidic acid, sold under the brand name Fucidin among others, is an antibiotic that is often used topically in creams or ointments and eyedrops but may also be given systemically as tablets or injections. As of October 2008, the global problem of advancing antimicrobial resistance has led to a renewed interest in its use.

Key takeaways

Fusidic acid belongs to chemistry; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Fusidic acid to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Fusidic acid from memory before moving on to harder problems.

Reference excerpt

Fusidic acid, sold under the brand name Fucidin among others, is an antibiotic that is often used topically in creams or ointments and eyedrops but may also be given systemically as tablets or injections. As of October 2008, the global problem of advancing antimicrobial resistance has led to a renewed interest in its use.

Medical uses Fusidic acid is active in vitro against Staphylococcus aureus, most coagulase-positive staphylococci, Beta-hemolytic streptococci, Corynebacterium species, and most clostridium species. Fusidic acid has no known useful activity against enterococci or most Gram-negative bacteria (except Neisseria, Moraxella, Legionella pneumophila, and Bacteroides fragilis). Fusidic acid is active in vitro and clinically against Mycobacterium leprae but has only marginal activity against Mycobacterium tuberculosis. One use of fusidic acid is its activity against methicillin-resistant Staphylococcus aureus (MRSA). Although many strains of MRSA remain sensitive to fusidic acid, there is a low genetic barrier to drug resistance (a single point mutation is all that is required). Fusidic acid should never be used on its own to treat serious MRSA infection and should be combined with another antimicrobial such as rifampicin when administering oral or topical dosing regimens approved in Europe, Canada, and elsewhere. However, resistance selection is low when pathogens are challenged at high drug exposure. Topical fusidic acid is occasionally used as a treatment for acne vulgaris. As a treatment for acne, fusidic acid is often partially effective at improving acne symptoms. However, research studies have indicated that fusidic acid is not as highly active against Cutibacterium acnes as many other antibiotics that are commonly used as acne treatments. Fusidic acid is also found in several additional topical skin and eye preparations (e.g., Fucibet), although its use for these purposes is controversial.

Side effects Fucidin tablets and suspension, whose active ingredient is sodium fusidate, occasionally cause liver damage, which can produce jaundice (yellowing of the skin and the whites of the eyes). This condition will almost always get better after the patient finishes taking Fucidin tablets or suspension. Other related side-effects include dark urine and lighter-than-usual feces. These, too, should normalize when the course of treatment is completed.

Pharmacology Fusidic acid acts as a bacterial protein synthesis inhibitor by preventing the turnover of elongation factor G (EF-G) from the ribosome. Fusidic acid is effective primarily on Gram-positive bacteria such as Staphylococcus, Streptococcus and Corynebacterium species. Fusidic acid is a tetracyclic, naturally occurring steroid derived from the fungus Fusidium coccineum. It was first isolated in 1960 and developed by Leo Pharma in Ballerup, Denmark, being used clinically from 1962 onwards. It has also been isolated from Mucor ramannianus, an Acremonium species, and Isaria kogana. The drug is licensed for use as its sodium salt sodium fusidate, and it is approved for use under prescription in Australia, Canada, Colombia, the European Union, India, Japan, New Zealand, South Korea, Taiwan, Thailand, and the United Kingdom.

Mechanism of action Fusidic acid binds to EF-G after translocation and GTP (guanosine-5'-triphosphate) hydrolysis. This interaction prevents the necessary conformational changes for EF-G release from the ribosome, effectively blocking the protein synthesis process. Fusidic acid can only bind to EF-G in the ribosome after GTP hydrolysis. Since translocation is a part of elongation and ribosome recycling, fusidic acid can block either or both steps of protein synthesis.

Dose Fusidic acid should not be used on its own to treat S. aureus infections when used at low drug dosages. However, it may be possible to use fusidic acid as monotherapy when used at higher doses. The use of topical preparations (skin creams and eye ointments) containing fusidic acid is strongly associated with the development of resistance, and there are voices advocating against the continued use of fusidic acid monotherapy in the community. Topical preparations used in Europe often contain fusidic acid and gentamicin in combination, which helps to prevent the development of resistance.

Cautions There is inadequate evidence of safety in human pregnancy. Animal studies and many years of clinical experience suggest that fusidic acid is devoid of teratogenic effects (birth defects), but fusidic acid can cross the placental barrier.

Resistance In vitro susceptibility studies of US strains of several bacterial species such as S. aureus, including MRSA and coagulase negative Staphylococcus, indicate potent activity against these pathogens. Mechanisms of resistance have been extensively studied only in Staphylococcus aureus. The most studied mechanism is the development of point mutations in fusA, the chromosomal gene that codes for EF-G. The mutation alters EF-G so that fusidic acid is no longer able to bind to it. Resistance is readily acquired when fusidic acid is used alone and commonly develops during the course of treatment. As with most other antibiotics, resistance to fusidic acid arises less frequently when used in combination with other drugs. For this reason, fusidic acid should not be used on its own to treat serious Staph. aureus infections. However, at least in Canadian hospitals, data collected between 1999 and 2005 showed rather low rate of resistance of both methicillin-susceptible and methicillin-resistant to fusidic acid, and mupirocin was found to be the more problematic topical antibiotic for the aforementioned conditions. Some bacteria also display 'FusB-type' resistance, which has been found to be the most prevalent in Staphylococcus spp. in many clinical isolates. This resistance mechanism is mediated by fusB, fusC, and fusD genes found primarily on plasmids, but have also been found in chromosomal DNA. The product of fusB-type resistance genes is a 213-residue cytoplasmic protein which interacts in a 1:1 ratio with EF-G. FusB-type proteins bind in a region distinct from fusidic acid to induce a conformational change which results in liberation of EF-G from the ribosome, allowing the elongation factor to participate in another round of ribosome translocation.

… excerpt ends here. Continue reading the full article.

Illustrations

Worked examples

Example 1 — a first encounter with Fusidic acid

Start with the simplest possible case. Write down what Fusidic acid claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In chemistry, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Fusidic acid before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Fusidic acid ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Fusidic acid

In research: Fusidic acid appears in chemistry research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Fusidic acid in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Fusidic acid is common in secondary-school and first-year university syllabi. It links to neighbouring topics Acetate esters, Alkene derivatives, CYP2D6 inhibitors, so understanding it makes those chapters shorter.
In everyday life: Look for Fusidic acid outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Fusidic acid in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Fusidic acid means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Fusidic acid out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Fusidic acid in simple terms?

Why does Fusidic acid matter?

Because it connects several chemistry ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Fusidic acid?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Fusidic acid.