THE PET PHARMACY By Wendy C. Brooks, DVM, DipABVP Educational Director, VeterinaryPartner.com

(for veterinary information only)

Brand Name: Lamisil

Available in 250 mg tablets and 1% gel for topical use  

Background

Animal cells differentiate from bacterial, fungal, and plant cells by the presence of a cell wall (animal cells have a cell membrane instead). The cell wall is thicker than a cell membrane and is made of different biochemical substances. These differences can be exploited so as to create medicines active against the cells of infectious agents but that are harmless to animal cells. The fungal cell wall, for example, contains a material known as ergosterol. 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.

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.

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 (ketaconazole, itraconazole) has.

Interactions with other Drugs

No definitive interactions are known, however, many other drugs share the same inactivation pathway as terbinafine: selegiline, beta blockers, 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.

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.
  

It is our policy not to give dosing information over the Internet.

Date Published: 5/9/2005 11:41:00 AM
Date Reviewed/Revised: 01/16/2009