TERBINAFINE

(for veterinary information only)

BRAND NAMES: ALAMIL, DASKIL, DASKYL, FINEX, LAMISIL, MICOCIL, TEREKOL

AVAILABLE IN
250 mg
TABLETS,
FILM-COATED ORAL GRANULES
as well as a
1% GEL
for topical use

BACKGROUND

Treatment of infection centers on exploiting a biological difference between the infectious agent and its host so that the infectious agent can be killed and the host will be unaffected. In the case of the fungal infection, the cell wall of the fungus is the usual focus anti-fungal medication. Happily, fungal cells (as well as bacterial and plant cells) employ a fibrous cell wall to encase their inner structures while animal cells utilize a "cell membrane" which is a completely different structure. The fungal cell wall forms a thick armor and contains a special form of vitamin D known as ergosterol without which many fungi cannot live. Terbinafine inhibits the production of ergosterol in such a way as to lead to the build up of the ergosterol precursor known as squalene. Having the wrong structural components disrupts the function of the cell wall as a barrier. Without the protection of its outer armor (the cell wall), the fungal cell will die.  None of this affects the animal cell because animal cells, as mentioned, do not even have cell walls.

HOW THIS MEDICATION IS USED

After terbinafine is taken orally, it concentrates in the skin and fat tissues of the body. The high levels in the skin make terbinafine an ideal treatment for fungal infection of the skin. For veterinary patients this typically would relate to ringworm infection (dermatophytosis). Terbinafine has activity against other types of fungi (in particular, Aspergillus species) but at this time it is mostly used against ringworm. Terbinafine is dosed 1-3 times daily depending on what fungus is being treated.

SIDE EFFECTS

The most common side effect is upset stomach. More rarely but also more seriously, there have been cases of liver failure, skin reactions, and bone marrow suppression.

Because terbinafine uses a different mechanism of ergosterol inhibition, it does not have the hormonal side effects that the "azole" group of antifungals (ketoconazole, itraconazole) has.

INTERACTIONS WITH OTHER DRUGS

No definitive interactions are known, however, many other drugs are removed from the body via the same inactivation pathway as terbinafine: selegiline (an MAO inhibitor), amitraz (a common tick killing product), beta blockers (heart medicines), tricyclic antidepressants (like clomipramine and amitriptyline), and selective serotonin reuptake inhibitors (like fluoxetine). This means there is potential for interaction though nothing has been reported at this time.

Terbinafine may facilitate the removal of cyclosporine (an immune-modulator used in the treatment of immune-mediated diseases as well as allergy) from the body. This means that cyclosporine will not be as effective in the presence of terbinafine.

Concurrent use of the antacid cimetidine will slow removal of terbinafine from the body (thus increasing its levels).

CONCERNS AND CAUTIONS

• Terbinafine should be stored at room temperature and protected from light exposure.
• Oral terbinafine works best when given with food.
• Terbinafine should not be used in patients with kidney or liver disease.
• Terbinafine should not be used in pregnancy or lactation.
• If you accidentally skip a dose, do not double up on the next dose. Simply pick up normally with the next dose.

 Page last updated: 8/8/2019