Terbinafine
An allylamine antifungal: tablets for fungal nail infections, and creams, gels or sprays for ringworm and athlete's foot.
Drug card
- Class
- Allylamine
- How it works
- Inhibiting squalene epoxidase, so toxic squalene builds up in the fungus
- Used for
- Fungal nail infection (onychomycosis), as tablets
- Ringworm, athlete's foot and jock itch
- Candida skin infections (cream)
- Known for
- Taste disturbance or loss, sometimes permanent
- Liver failure, sometimes needing a transplant
Study it as a flashcard, and it comes back before you forget it.
Mechanism of action
How does terbinafine work?
Terbinafine inhibits fungal squalene epoxidase. Ergosterol synthesis stops and squalene accumulates to high levels, making the membrane leaky and killing the fungus. It acts well against the dermatophytes Trichophyton rubrum and T. mentagrophytes. It also inhibits human CYP2D6, so people may handle CYP2D6 drugs like poor metabolizers for weeks after stopping it.
Uses
What is terbinafine used for?
- Fungal nail infection (onychomycosis), as tablets
- Ringworm, athlete's foot and jock itch
- Candida skin infections (cream)
Side effects
Side effects of terbinafine
- Taste disturbance or loss, sometimes permanentKnown for
- Liver failure, sometimes needing a transplantKnown forSerious
- Headache
- Diarrhea
- Nausea
- Rash and itching
- Smell disturbance or loss
- Low mood and depressive symptoms
- Severe neutropeniaSerious
- Severe skin reactions such as SJS, TEN and DRESSSerious
- New or worse lupusSerious
- Irritation where the cream is applied
Known for marks what an exam expects you to know it for.
Watch for
Cautions and what sets it apart
- Contraindicated in chronic or active liver disease; check liver tests before starting and during treatment.
- Inhibits CYP2D6: tricyclics, SSRIs, some beta blockers and flecainide may need lower doses.
- Stop it if taste or smell changes, depressive symptoms or signs of lupus appear.
- Check a blood count if signs of infection appear, and stop it if severe neutropenia is found.
Good to know: The usual tablet for fungal nail infections, which take 3 months or more to clear; on the skin it is a common cream for athlete's foot and ringworm.
Remember it
A way to remember it
Allylamines drown the fungus in squalene.
By blocking squalene epoxidase, terbinafine makes squalene pile up inside the fungus. The excess squalene makes the membrane leaky and kills the cell, more than the missing ergosterol does.
Written for biofideX
Its class
Allylamines
Allylamines inhibit squalene epoxidase, an enzyme of fungal ergosterol synthesis that differs from the azoles' target. Ergosterol production stops and squalene builds up to high levels inside the fungus; the squalene excess, more than the ergosterol shortage, makes the membrane leaky and kills the cell, so they can be fungicidal. Terbinafine is the main member.
Easily mixed up with azole antifungals and polyene antifungals.
Sources
Checked against
Written for biofideX in plain words, after checking these references:
For learning pharmacology, not for treatment decisions: no doses are given, and a prescriber, pharmacist or the product's own label is the word on any one patient. Spotted a mistake? Tell us and we'll correct it.
Antifungals and antiparasitics
Terbinafine is one of 14 drugs practiced together here: their classes, how they work, what they treat and what they're known for.
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