Terbinafine is an antifungal medication primarily used to treat fungal infections of the skin and nails, such as athlete's foot, ringworm, and fungal nail infections. It is available in various forms, including oral tablets, creams, and sprays.

Terbinafine (Lamisil) is an antifungal medicine that is available both as oral tablets and topical formulations for the treatment of fungal infections.

• Onychomycosis (tablets only):
  • It is used to treat dermatophyte-caused onychomycosis of the toenail or fingernail (tinea unguium).
• Tinea capitis (granules only):
  • Patients 4 years of age and older can use it to treat tinea capitis.
• Off Label Usage of Terbinafine in Adults:
• It is also used in following conditions:
  • Dermatophyte folliculitis (tinea barbae, Majocchi granuloma);
  • Sporotrichosis (lymphocutaneous and cutaneous);
  • Tinea capitis;
  • Tinea corporis/tinea cruris/tinea faciei;
  • Tinea pedis/tinea manuum

Terbinafine Dose in Adult

Terbinafine dosage in the treatment of Onychomycosis:

Continuous Dosing:

• For fingernail fungus: Take 250 mg of terbinafine in tablet form once a day for 6 weeks.
• For toenail fungus: Take 250 mg of terbinafine in tablet form once a day for 12 weeks.

Pulsed Dosing (an alternative method that's not standard but sometimes used):

• Method 1: Take 250 mg once daily for 4 weeks, then take no medicine for the next 4 weeks, and then repeat another 4 weeks of 250 mg once daily.
• Method 2: Take 250 mg twice daily for 1 week, then take no medicine for the next 3 weeks. This cycle is repeated for 3 months.

Pulsed dosing might be chosen because it can potentially lessen side effects, lower costs, and make it easier for patients to stick to their treatment plan, although it's generally less effective than continuous dosing.

Terbinafine Dosage in the treatment of Sporotrichosis, lymphocutaneous and cutaneous (alternative agent for patients who do not respond to itraconazole) (off-label):  

• Dose: Take 500 mg of terbinafine orally, twice daily.
• Duration: Continue the treatment for 2 to 4 weeks after all lesions have healed. Typically, the total treatment period lasts between 3 to 6 months, depending on the response and severity of the infection.

This dosage and treatment duration is based on guidelines and recommendations from sources like the Infectious Diseases Society of America (IDSA).

Terbinafine Dosage in the treatment of Tinea infections:

• Dermatophyte Folliculitis (such as tinea barbae and Majocchi granuloma):
  • Dose: 250 mg orally, once daily.
  • Duration: Typically 2 to 6 weeks, but may need to be extended, especially in immunocompromised patients or those with a slow response.
• Tinea Capitis:
  • Dose: 250 mg orally, once daily.
  • Duration: 4 to 6 weeks.
• Tinea Corporis, Tinea Cruris, Tinea Faciei:
  • Note: This is an alternative treatment option for patients with extensive skin involvement or when topical therapy has failed.
  • Dose: 250 mg orally, once daily.
  • Duration: 1 to 2 weeks.
• Tinea Pedis (athlete’s foot) and Tinea Manuum (hand fungus):
  • Note: Used as an alternative treatment for cases with extensive skin involvement or when topical therapy has failed.
  • Dose: 250 mg orally, once daily.
  • Duration: 2 weeks.

Terbinafine dose in Children

Terbinafine Dosage in the treatment of Tinea capitis:

• Children weighing less than 25 kg: 125 mg once daily for 6 weeks.
• Children weighing 25 to 35 kg: 187.5 mg once daily for 6 weeks.
• Children weighing more than 35 kg: 250 mg once daily for 6 weeks.

It's important for this treatment to continue for the full duration to ensure the infection is completely cleared. This dosing applies specifically to children who are 4 years of age and older.

Terbinafine dosage in the treatment of Onychomycosis:

• Children weighing 10 to 20 kg:
  • 62.5 mg once daily
  • Duration: 6 weeks for fingernails, 12 weeks for toenails
• Children weighing 20 to 40 kg:
  • 125 mg once daily
  • Duration: 6 weeks for fingernails, 12 weeks for toenails
• Children weighing over 40 kg:
  • 250 mg once daily
  • Duration: 6 weeks for fingernails, 12 weeks for toenails

This treatment plan should be monitored closely by a healthcare provider, especially considering the varying durations based on the location of the fungal infection (fingernails vs. toenails) and the limited data available on pediatric use for this condition. It's crucial to ensure that the dosing is appropriate for the child's weight and the severity of the infection.

Terbinafine pregnancy Risk category: B

• There is limited information about the safety of using systemic terbinafine (taken by mouth) during pregnancy.
• Therefore, it is generally not recommended to use this medication for treating fungal infections like onychomycosis (nail fungus) or tinea capitis (scalp fungus) when pregnant.
• This recommendation is based on concerns about potential risks to the developing baby.

Terbinafine use during breastfeeding:

• Terbinafine can pass into breast milk, with a breastfed baby receiving around 4% of the dose their mother takes.
• Due to this, it's generally not recommended to breastfeed while undergoing systemic (oral) terbinafine therapy for fungal infections.
• However, the decision to breastfeed during treatment should be carefully weighed, considering factors such as the potential risk of the infant being exposed to the medication, the benefits of breastfeeding for the baby, and the benefits of the treatment for the mother's health.

Terbinafine (Lamisil) dose in renal disease:

• The manufacturer's instructions don't include specific dosage adjustments for different situations because it hasn't been studied.
• However, it's noted that in patients with a reduced kidney function (measured as creatinine clearance of 50 mL/minute or less), the body clears terbinafine at a slower rate, about 50% slower than usual.

Terbinafine Dose in Liver Disease:

• If someone has chronic or active liver disease, it's not safe for them to take terbinafine.
• This medication is not recommended for people with liver problems because it could potentially worsen their condition or cause further damage to the liver.

Common Side Effects of Terbinafine Include:

• Central nervous system:
  • Headache

Less Common Side Effects of Terbinafine Include:

• Dermatologic:
  • Skin Rash
  • Pruritus
  • Urticaria
• Gastrointestinal:
  • Diarrhea
  • Vomiting
  • Dyspepsia
  • Upper Abdominal Pain
  • Dysgeusia
  • Nausea
  • Abdominal Pain
  • Pharyngolaryngeal Pain
  • Toothache
• Hepatic:
  • Liver Enzyme Disorder
• Infection:
  • Influenza
• Ophthalmic:
  • Vision Color Changes
  • Decreased Visual Acuity
• Respiratory:
  • Nasopharyngitis
  • Cough
  • Upper Respiratory Tract Infection
  • Nasal Congestion
  • Rhinorrhea
• Miscellaneous:
  • Fever

Contraindication to Terbinafine Include:

• If someone is allergic to terbinafine or any part of the medication, or if they have chronic or active liver disease, they should not take terbinafine.
• This is because it could trigger an allergic reaction or worsen their liver condition.

Warnings and precautions

Antifungal hypersensitivity to Allylamine

• If someone is sensitive or allergic to allylamine antifungal medications like naftifine or butenafine, they should be cautious when using terbinafine.
• There's a possibility of cross-sensitivity, meaning that their body might react to terbinafine similarly to how it reacts to other allylamine antifungals.

Depression

• Some people have reported experiencing depression while using terbinafine.
• Patients should be instructed to report any symptoms of depression or changes in mood while taking this medication.

Gastrointestinal effects:

• Terbinafine can sometimes cause gastrointestinal issues, including taste disturbances such as a loss of taste.
• In severe cases, this can lead to decreased food intake, weight loss, and even feelings of anxiety or depression.
• It's important to note that these taste disturbances may not resolve immediately after stopping the medication and could take several weeks to over a year to improve, or in some cases, the disturbance may be permanent.

Hematologic effects

• Terbinafine can sometimes affect blood cell counts, particularly lymphocytes and neutrophils.
• In clinical trials, temporary decreases in lymphocyte counts were observed, and in rare cases, severe neutropenia (low levels of neutrophils) has occurred, which typically reverses after stopping the medication.
• If terbinafine therapy is planned to continue for longer than 6 weeks in patients with preexisting immune system suppression, it's important to monitor their complete blood count (CBC).
• If the absolute neutrophil count (ANC) falls below 1,000/mm³, it's recommended to discontinue terbinafine therapy.

Hepatic failure

• Terbinafine has been associated with cases of hepatic failure, some of which have led to liver transplant or death.
• This serious side effect can occur in patients both with and without preexisting liver disease.
• Hepatic events may be more severe in patients with active or chronic liver conditions.
• To monitor for liver problems, it's important to conduct baseline and periodic liver function tests while using terbinafine.
• If any signs of liver injury develop, such as nausea, loss of appetite, fatigue, vomiting, abdominal pain (especially in the upper right area), jaundice (yellowing of the skin or eyes), dark urine, or pale stools, or if liver function tests show elevated levels, terbinafine should be discontinued promptly.
• Early detection and discontinuation of the medication are crucial to prevent further liver damage.

Hypersensitivity

• Terbinafine can trigger serious skin and hypersensitivity reactions, such as Stevens-Johnson syndrome, toxic epidermal necrolysis, erythema multiforme, exfoliative dermatitis, bullous dermatitis, and drug reaction with eosinophilia and systemic symptoms (DRESS) syndrome.
• If a patient develops a progressive skin rash or shows signs and symptoms of a hypersensitivity reaction while taking terbinafine, it's crucial to discontinue the treatment immediately.
• These reactions can be severe and potentially life-threatening, so prompt action is essential to ensure the patient's safety.

Ocular effects

• While rare, terbinafine use has been associated with changes in the ocular lens and retina.
• These ocular effects may occur, prompting the need for discontinuation of therapy.
• If a patient experiences any changes in vision or other ocular symptoms while taking terbinafine, it's important to seek medical attention promptly.
• Ophthalmologic evaluation may be necessary to assess the extent of ocular changes and determine whether discontinuing the medication is necessary to prevent further complications.

Respiratory effects

• Terbinafine use has been associated with respiratory effects, particularly disturbances in smell, including loss of smell.
• In some cases, these disturbances may persist even after discontinuation of therapy, and in rare instances, they may become permanent.
• If a patient experiences symptoms of smell disturbance while taking terbinafine, it's important to discontinue the therapy and seek medical advice.
• Resolution of these symptoms may take time, with some cases taking over a year to improve.
• However, if the disturbance persists or becomes permanent, further evaluation and management may be necessary.

Thrombotic microangiopathy

• Terbinafine use has been associated with cases of thrombotic microangiopathy (TMA), including serious conditions like thrombotic thrombocytopenic purpura and hemolytic uremic syndrome.
• Some of these cases have been fatal.
• If a patient develops symptoms suggestive of TMA, such as unexplained thrombocytopenia (low platelet count) and anemia (low red blood cell count), it's important to consider the possibility of TMA and promptly discontinue terbinafine therapy.
• Early recognition and discontinuation of the medication are crucial in managing this potentially life-threatening condition.

Autoimmune disease (Lupus).

• Terbinafine use has been linked to the precipitation or worsening of both cutaneous (skin) and systemic (affecting multiple organs) lupus erythematosus, an autoimmune disease.
• If signs or symptoms of lupus, such as skin rashes, joint pain, or other systemic symptoms, develop while taking terbinafine, it's important to discontinue the medication.
• This precaution is essential to prevent further exacerbation of lupus symptoms and to manage the condition appropriately.

Hepatic impairment

• Terbinafine use is not recommended for individuals with active or chronic liver disease.
• The medication is contraindicated in such cases.
• Even in patients with hepatic cirrhosis, terbinafine clearance is reduced by approximately 50%.
• Therefore, caution should be exercised, and alternative treatments may be considered for patients with hepatic impairment to avoid potential adverse effects and further liver damage.

Renal impairment

• In patients with renal dysfunction, particularly those with a creatinine clearance (CrCl) of 50 mL/minute or less, terbinafine should be used cautiously.
• The clearance of terbinafine is reduced by approximately 50% in such individuals.

Terbinafine (systemic): Drug Interaction

Monitor:

• Liver Function Tests:
  • Conduct liver function tests before starting terbinafine and regularly during treatment to check for any signs of liver damage or dysfunction.
• Complete Blood Count (CBC):
  • If terbinafine treatment extends beyond 6 weeks or in immunosuppressed patients, consider monitoring CBC to assess for any abnormalities in blood cell counts.
• Taste and Smell Disturbances:
  • Be alert to any changes in taste or smell, including loss of taste or smell, as these can be potential side effects of terbinafine. If such disturbances occur, discontinue therapy and seek medical advice.

How to administer Terbinafine (lamisil)?

Administration of Tablets:

• Tablets can be taken with or without food. There's no need to consider meals when taking the tablet form of terbinafine.

Administration of Granules:

• Granules should be taken with food.
• To administer granules, sprinkle them on a spoonful of soft, nonacidic food such as pudding or mashed potatoes.
• Swallow the entire spoonful without chewing.
• Avoid mixing granules with applesauce or other fruit-based foods.

Mechanism of action of Terbinafine (Lamisil):

• Terbinafine is a synthetic compound belonging to the allylamine class.
• It works by inhibiting an enzyme called squalene epoxidase, which is crucial for fungi to make a substance called ergosterol.
• Ergosterol is essential for the fungal cell membrane.
• By blocking its production, terbinafine causes a shortage of ergosterol, weakening the fungal cell membrane and leading to the death of the fungus.

Absorption:

• Terbinafine is well absorbed in both children and adults, with over 70% of the dose being absorbed into the bloodstream.

Distribution:

• After absorption, terbinafine is distributed mainly to sebum (oily substance) and skin tissues.

Protein Binding:

• In the bloodstream, terbinafine is highly bound to proteins, with over 99% of the drug being bound to plasma proteins.

Metabolism:

• Terbinafine is primarily metabolized in the liver, predominantly by enzymes such as CYP1A2, 3A4, 2C8, 2C9, and 2C19, leading to the formation of inactive metabolites.

Bioavailability:

• The bioavailability of terbinafine ranges from 36% to 64% in children and approximately 40% in adults.

Half-life Elimination:

• The terminal half-life of terbinafine is long, ranging from 200 to 400 hours. However, the effective half-life, which takes into account the slow release of the drug from skin and adipose tissues, is shorter, lasting around 27 to 31 hours in children and approximately 36 hours in adults.
• Time to reach peak levels in the bloodstream occurs within 2 hours after administration in both children and adults.

Excretion:

• Terbinafine and its metabolites are primarily eliminated through the urine (about 80% of the dose), with a smaller portion being excreted in feces (about 20%).

Clearance:

• The clearance of terbinafine varies in children, ranging from 15.6 to 26.7 L/hour depending on body weight.

International Brands of Terbinafine:

• ACT Terbinafine
• APO-Terbinafine
• Auro-Terbinafine
• DOM-Terbinafine
• JAMP-Terbinafine
• LamISIL
• MYLAN-Terbinafine
• PHL-Terbinafine
• PMS-Terbinafine
• RIVA-Terbinafine
• SANDOZ Terbinafine
• Terbinafine-250
• TEVA-Terbinafine
• Amizil
• Antifin
• Atifan
• Camisan
• Cutis
• Deolate
• Derfin
• Dermafin
• Dermasil
• Dermatin
• Dermax
• Dicil
• EU2000
• Finex
• Fungasil
• Funginix
• Fungitech
• Fungizid
• Fungotek
• Fungster
• Funzal
• Interbi
• L:isim
• Lamifen
• Lamisil
• Lamisil AT
• Lamisil Dermgel
• Lamisil Once
• Lamisilate
• Lammifen
• Lapiderm
• Micoset
• Micozone
• Muzona
• Mycelvan
• Nailderm
• Patir
• Periafin
• Ronasil Derm Gel
• Sebifin
• Skinabin
• SolvEasy Tinea Cream
• Tamsil
• Tenabin
• Terbex
• Terbicip
• Terbifin
• Terbihexal
• Terbin
• Terbix
• Terekol
• Terfex
• Terfine
• Terfung
• Tiersil Once
• Zabel

Terbinafine brands in Pakistan: