terbinafine

Action and Spectrum

Actions and Spectrum: 

The actions and spectrum of terbinafine include: 

• Antifungal activity: terbinafine is active against a wide range of fungal species, including dermatophytes (such as Trichophyton, Microsporum, and Epidermophyton), yeasts (such as Candida), and molds (such as Aspergillus). It is especially effective against dermatophytes, the most common cause of fungal skin infections. 
• Fungicidal activity: terbinafine is a fungicidal agent, killing fungal cells rather than inhibiting their growth. 
• Long-lasting effects: terbinafine has a long half-life, which allows for once-daily dosing and sustained activity against fungal infections. 
• Low risk of resistance: terbinafine has a low risk of inducing resistance in fungal species, making it an effective long-term treatment option. 

Drug Interaction

Adverse Reaction

Frequency Defined 

>10 

Headache 

1-10% 

Rash  

Pruritus  

Dyspepsia  

Abdominal pain  

Nausea  

Diarrhea  

Elevated LFT   

Visual disturbance 

Taste disturbance 

Black Box Warning

Contraindication / Caution

Contraindication/Caution: 

Contraindications: 

• Hypersensitivity: terbinafine should not be used in patients with known hypersensitivity or allergy to the drug or its components. 
• Liver disease: terbinafine is primarily metabolized in the liver and can cause hepatotoxicity in some patients. It should be used cautiously in patients with pre-existing liver disease or a history of liver problems. 
• Pregnancy and breastfeeding: terbinafine is not recommended in pregnant or breastfeeding women due to limited data on its safety in these populations. 

Precautions: 

• Renal impairment: terbinafine is primarily excreted by the kidneys, and dosage adjustments may be necessary for patients with impaired renal function. 
• Drug interactions: terbinafine can interact with other medications, including specific antifungal agents, antidepressants, and beta-blockers. It is essential to check for potential drug interactions before starting terbinafine. 
• Skin reactions: terbinafine can rarely cause severe skin reactions, such as Stevens-Johnson syndrome or toxic epidermal necrolysis.  
• Immunocompromised patients: terbinafine may be less effective in patients with weakened immune systems, such as HIV or cancer. These patients may require longer treatment courses or additional antifungal medications. 

Pregnancy / Lactation

Pregnancy consideration:  

terbinafine is not recommended during pregnancy 

Breastfeeding warnings:  

No data available  

Pregnancy category: 

• Category A: Satisfactory and well-controlled studies show no risk to the fetus in the first or later trimester. 
• Category B: No evidence of risk to the fetus is found in animal reproduction studies, and there are not enough studies on pregnant women. 
• Category C: Adverse effects on the fetus found with evidence in animal reproduction studies and no adequate evidence for a human product; Pregnant women must take care of the potential risks. 
• Category D: There is adequate data with sufficient evidence of human fetal risk from various platforms. However, despite potential dangers may be used only in emergencies for potential benefits. 
• Category X: Drugs listed in this category outweigh the risks over benefits. The drug is not for pregnant women. 
• Category N: No data for the drug under this category is available. 

Pharmacology

Pharmacology: 

terbinafine is an antifungal medication commonly used to treat fungal infections, including ringworm, athlete’s foot, and nail fungus. It is available in several forms, including tablets, creams, and topical solutions. 

terbinafine works by inhibiting the synthesis of ergosterol, a key component of fungal cell membranes. It disrupts the fungal cell membrane and ultimately leads to the death of the fungus. 

Pharmacodynamics 

terbinafine exerts its antifungal activity by inhibiting the synthesis of ergosterol, an essential component of fungal cell membranes. Ergosterol is required for the integrity of fungal cell membranes and the proper functioning of membrane-bound enzymes. terbinafine specifically targets the enzyme squalene epoxidase, which catalyzes the conversion of squalene to lanosterol, an early step in ergosterol biosynthesis. 

By inhibiting squalene epoxidase, terbinafine blocks the production of ergosterol and leads to the accumulation of squalene, which is toxic to the fungal cell. It ultimately results in the disruption of the fungal cell membrane and the death of the fungus. 

terbinafine has a broad spectrum of activity against various fungi, including dermatophytes, yeasts, and molds. It is particularly effective against dermatophytes, which are responsible for most cases of superficial fungal infections. 

terbinafine is generally fungicidal, killing the fungal cells directly rather than simply inhibiting their growth. It is effective against both superficial and systemic fungal infections. 

Pharmacokinetics: 

Absorption 

Absorption is more than 70% 

Bioavailability is 40% for adults and 36-64% for children 

The peak plasma concentration is achieved in 1-2 hours 

The peak plasma concentration for a 250-mg dose is one mcg/mL 

Distribution 

The drug is predominantly distributed in the skin and sebum 

The protein-bound is more than 99% 

The volume of distribution is 2000 L 

Metabolism 

The drug is metabolized in the liver by several CYP450 enzymes 

40% first-pass effect is seen 

Metabolites: Inactive 

Inhibition occurs by CYP2D6 

Elimination and Excretion  

The half-life is 36 hours (The drug gets released very slowly from the skin and adipose tissues) 

The drug is 70% excreted in the urine. 

Adminstartion

Administration: 

terbinafine is available in several forms, including tablets, creams, and topical solutions. The route of administration will depend on the specific type and location of the fungal infection being treated. 

Topical terbinafine is usually applied directly to the affected area for superficial fungal infections such as athlete’s foot and ringworm. The cream or solution should be applied to the affected skin or nails once or twice a day for several weeks, depending on the severity of the infection. 

terbinafine should be taken with a full glass of water and with or without food. It is essential to take the medication exactly as prescribed and complete the entire treatment course, even if the symptoms improve before the medication is finished. 

Patient Information Leaflet

Patient information leaflet 

Generic Name:  terbinafine  

Pronounced: ter-bina-fine 

Why do we use terbinafine? 

terbinafine is primarily used to treat fungal infections, particularly those caused by dermatophytes, responsible for most superficial fungal infections. These may include ringworm, athlete’s foot, jock itch, and nail fungus. 

terbinafine is also effective against other fungal infections, including yeast and mold. It can be administered topically as a cream or solution for mild to moderate infections or orally in tablet form for more severe or systemic infections. 

terbinafine is a particularly effective antifungal medication because it specifically targets the enzyme squalene epoxidase, essential for synthesizing ergosterol, a key component of fungal cell membranes. This results in the disruption of the fungal cell membrane and ultimately leads to the death of the fungus.