Terbinafine is a medication that combats fungal infections. It belongs to a class of drugs known as allylamine antifungals. Terbinafine targets and eliminates fungi responsible for infections affecting the skin, hair, and nails. This medication is available in different forms, including topical applications like creams, gels, and sprays, as well as oral tablets.
Common Fungal Infections it Treats
Terbinafine treats a range of fungal infections, particularly those caused by dermatophytes, which are a group of fungi that thrive on keratin in skin, hair, and nails. It addresses athlete’s foot, medically known as tinea pedis, which typically causes itching, scaling, and redness between the toes or on the soles of the feet. Another infection is jock itch, or tinea cruris, characterized by an itchy, red rash in the groin area.
Ringworm, or tinea corporis, which presents as a circular, red, scaly rash on the body, also responds to terbinafine. For these skin infections, topical forms are often effective. Fungal nail infections, called onychomycosis, affecting fingernails and toenails, are also treated. These infections can lead to discolored, thickened, and brittle nails. Oral terbinafine is typically prescribed for nail infections because topical treatments may not adequately penetrate the nail to reach the infection.
How Terbinafine Works
Terbinafine interferes with the fungal cell’s ability to produce ergosterol, a substance comparable to cholesterol in human cells, which is an integral component of the fungal cell membrane. It achieves this by inhibiting a specific enzyme called squalene epoxidase. This enzyme converts squalene into a precursor to ergosterol production.
By blocking squalene epoxidase, terbinafine causes two effects within the fungal cell. First, it leads to an ergosterol deficiency, which compromises the integrity and function of the fungal cell membrane. Second, it causes squalene to build up to toxic levels inside the fungal cell, further weakening the cell membrane and ultimately leading to the fungus’s death. This action makes terbinafine effective against many fungi while having minimal impact on human cells, as human cells use cholesterol and have different enzyme structures.
Using Terbinafine Effectively
For topical applications, used for skin infections like athlete’s foot or ringworm, instructions involve applying the product once or twice daily for one to two weeks. Cover the affected area completely and continue treatment for the full recommended duration, even if symptoms improve quickly, to prevent the infection from returning.
Oral terbinafine tablets are prescribed for more extensive or stubborn infections, such as fungal nail infections. The dosage for adults is one 250 mg tablet taken once daily. For fingernail infections, treatment lasts about six weeks, while toenail infections require a longer course of 12 weeks. If a dose is missed, take it as soon as remembered, unless it is close to the next scheduled dose, in which case skip the missed dose. Taking the medication consistently and completing the entire prescribed course is important to ensure the infection is fully cleared.
Important Safety Information
Like all medications, terbinafine can cause side effects, though most are mild and temporary. Common side effects of oral terbinafine include headache, nausea, diarrhea, indigestion, abdominal pain, and a temporary change or loss of taste. Skin irritation, redness, or itching are possible with topical applications. If using topical forms, applying smaller amounts or stopping use may help with irritation.
More serious side effects, while less common, can include severe allergic reactions, liver problems, or blood disorders. Symptoms of liver issues can include persistent nausea, vomiting, yellowing of the skin or eyes (jaundice), dark urine, or pale stools. Individuals with pre-existing liver disease should not use oral terbinafine. Terbinafine can also interact with other medications, as it affects certain liver enzymes. Discuss all current medications with a healthcare provider before starting terbinafine. Oral terbinafine is not recommended during pregnancy or breastfeeding, as it can pass into breast milk.