chemistry

Terbinafine

Terbinafine 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 Terbinafine rather than just read about it. In short: Terbinafine, sold under the brand name Lamisil among others, is an antifungal medication used to treat pityriasis versicolor, fungal nail infections, and ringworm including jock itch and athlete's foot. It is either taken by mouth or applied to the skin as a cream or ointment.

Key takeaways

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

Reference excerpt

Terbinafine, sold under the brand name Lamisil among others, is an antifungal medication used to treat pityriasis versicolor, fungal nail infections, and ringworm including jock itch and athlete's foot. It is either taken by mouth or applied to the skin as a cream or ointment. Common side effects when taken by mouth include nausea, diarrhea, headache, cough, rash, and elevated liver enzymes. Severe side effects include liver problems and allergic reactions. Liver injury is, however, unusual. Oral use during pregnancy is not typically recommended. The cream and ointment may result in itchiness but are generally well tolerated. Terbinafine is in the allylamines family of medications. It works by decreasing the ability of fungi to synthesize ergosterol. It appears to result in fungal cell death. Terbinafine was discovered in 1991. It is on the World Health Organization's List of Essential Medicines. In 2023, it was the 253rd most commonly prescribed medication in the United States, with more than 1 million prescriptions.

Medical uses Terbinafine is mainly effective on molds of the order Onygenales and some yeasts in the genus Candida. As a cream or powder, it is used topically for superficial skin infections such as jock itch (tinea cruris), athlete's foot (tinea pedis), and other types of ringworm (tinea corporis). Tablets by mouth are often prescribed for the treatment of onychomycosis, a fungal nail infection, typically by a dermatophyte or Candida species. Fungal nail infections are located deep under the nail in the cuticle to which topically applied treatments are unable to penetrate in sufficient amounts. The tablets may, rarely, cause hepatotoxicity, so patients are warned of this and may be monitored with liver function tests. Alternatives to oral administration have been studied. Terbinafine may induce or exacerbate subacute cutaneous lupus erythematosus. Persons with lupus erythematosus should first discuss possible risks with their doctor before initiation of therapy.

Side effects Many side effects and adverse drug reactions have been reported with oral terbinafine hydrochloride, possibly due to its extensive biodistribution and the often extended durations involved in antifungal treatment (longer than two months). A comprehensive list of adverse events associated with terbinafine use includes:

Gastrointestinal problems: Diarrhea, constipation, nausea, fullness, abdominal pain, indigestion, dyspepsia, gastritis, cholestasis, flatulence, altered stool colour, abdominal muscular pain Central nervous system or neurological problems: Headaches, dizziness, vertigo, light-headedness, decreased concentration levels, paraesthesia (pins and needles) Hepatic problems: Raised liver enzyme levels, liver inflammation (hepatitis), liver damage, liver failure Immune system problems: Decreased white blood cell counts including pancytopenia, leukopenia, lymphopenia, thrombocytopenia, agranulocytosis, and neutropenia, autoimmune reactions such as lupus erythematosus Psychological problems: Depression, anxiety, insomnia, increased or unusual dream activity, malaise Sensory problems: Complete loss of taste (ageusia), decreased taste (hypogeusia) and distorted taste (dysgeusia), often involving a metallic taste sensation and dry mouth, visual disturbances including blurred vision, green vision and double vision. In extremely rare cases, the loss or impairment of taste is permanent Auditory system problems: Tinnitus and hearing loss have been reported in rare cases. The Netherlands Pharmacovigilance Centre Lareb and WHO's global VigiBase database both reported multiple cases of tinnitus and hearing loss associated with oral terbinafine use. Skin problems: Rashes, hives (urticaria), skin irritation, itching, jaundice, Stevens–Johnson syndrome Other side effects: Fatigue, increased heart rate (tachycardia), hair loss (alopecia), decreased red blood cell count (anemia), muscle pain (myalgia), joint pain (arthralgia)

Pharmacology

Like other allylamines, terbinafine inhibits ergosterol synthesis by inhibiting squalene epoxidase, an enzyme that catalyzes the conversion of squalene to lanosterol. In fungi, lanosterol is then converted to ergosterol; in humans, lanosterol becomes cholesterol. However, as fungi and animals diverged around 1.1 billion years ago - there is enough difference in this enzyme that terbinafine preferentially binds fungal squalene epoxidase, making it selective for inhibiting ergosterol production in fungi without significantly affecting cholesterol production in mammals. This is thought to fatally disrupt the fungal cell membrane. Terbinafine is highly lipophilic and tends to accumulate in hair, skin, nails, and fat cells. This accumulation results in therapeutic levels of terbinafine even after 80 days following one week treatment of 250 mg/day.

Chemistry Terbinafine hydrochloride is a white crystalline powder that is freely soluble in methanol and dichloromethane, soluble in ethanol, and slightly soluble in water. Terbinafine is produced by coupling of 3,3-dimethyl-1-butyne (tert-butylacetylene) with acrolein as a key step, followed by coupling of the product of that reaction, 6,6-dimethylhept-1-en-4-yn-3-ol, with N-methyl-1-naphthalenemethanamine. Multiple patents and publication to alternate syntheses are available. Despite its name it does not contain terbium.

History Terbinafine first became available in Europe in 1991 and in the United States in 1996. The U.S. Food and Drug Administration has approved the first generic versions of prescription Lamisil (terbinafine hydrochloride) tablets. The remaining patent or exclusivity for Lamisil expired on 30 June 2007. On 28 September 2007, the FDA stated that terbinafine is now approved for use by children age four and up. The antifungal granules can be sprinkled on a child's food to treat scalp fungus. In the United States the price in 1999 was $547 for a 12-week course; this fell to $10 by 2015, after the patent had expired.

Society and culture

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Illustrations

Worked examples

Example 1 — a first encounter with Terbinafine

Start with the simplest possible case. Write down what Terbinafine 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 Terbinafine 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 Terbinafine 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 Terbinafine

In research: Terbinafine 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 Terbinafine 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: Terbinafine is common in secondary-school and first-year university syllabi. It links to neighbouring topics 1-Naphthyl compounds, Antifungals, CYP2D6 inhibitors, so understanding it makes those chapters shorter.
In everyday life: Look for Terbinafine 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 Terbinafine in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Terbinafine 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 Terbinafine out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Terbinafine in simple terms?

Why does Terbinafine 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 Terbinafine?

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 Terbinafine.