Terbinafine, an Allylamine antifungal, inhibits biosynthesis of Ergosterol (an essential component of fungai cell membrane) via inhibition of Squalene Epoxidase enzyme. This results in fungal cell death primarily due to the increased membrane permeability mediated by the accumulation of high concentrations of Squalene but not due to Ergosterol deficiency. Depending on the concentration of the drug and the fungal species test in vitro, Terbinafine hydrochloride may be fungicidal. However, the clinical significance of in vitro data is unknown. Terbinafine has been shown to be active against most strains of the following microorganisms both in vitro and in clinical infections: Tricophyton Mentagrophyte, Trichophyton Rubrum.

Terbinafine tablet:

• For the treatment of fingernail onychomycosis: Terbinafine 250 mg (one tablet), once daily for 6 weeks.
• For the treatment of toenail onychomycosis: Terbinafine 250 mg (one tablet), once daily for 12 weeks.
• The optimal clinical effect is seen some months after mycological cure and cessation of treatment. This is related to the period required for the outgrowth of healthy nail.

Terbinafine granules:

• Body Weight: <25 kg: 125 mg/day up to 6 weeks
• Body Weight: 25-35 kg: 187.5 mg/day up to 6 weeks
• Body Weight: >35 kg: 250 mg/day up to 6 weeks

Terbinafine cream: Terbinafine cream can be applied once or twice daily. Cleanse and dry the affected areas thoroughly before application of the terbinafine cream. Apply the cream to the affected skin and the surrounding area in a thin layer and rub in lightly. In the case of intertriginous infections (submammary, interdigital, intergluteal, inguinal) the application may be covered with a gauze strip, especially at night. The likely durations of treatment are as follows:

• Tinea corporis, cruris: 1 to 2 weeks
• Tinea pedis: 1 week
• Cutaneous candidiasis: 2 weeks
• Pityriasis versicolor: 2 weeks

Relief of the clinical symptoms usually occurs within a few days. Irregular use or premature discontinuation of treatment carries the risk of recurrence. If there are no signs of improvement after two weeks, the diagnosis should be verified.

Terbinafine 1% Spray: This spray is applied once or twice daily, depending on the indication. The affected areas should be cleansed and dried thoroughly before application of this spray. A sufficient amount of solution should be applied to wet the treatment area(s) thoroughly.

• Tinea pedis: once a day,1 week
• Tinea corporis/cruris: once a day,1 week
• Pityriasis versicolor: twice a day, 1 week

Relief of clinical symptoms usually occurs within a few days. If there are no signs of improvement after two weeks the diagnosis should be verified.

In vivo studies have shown that terbinafine is an inhibitor of the CYP450 2D6 isozyme. Drugs predominantly metabolized by the CYP450 2D6 isozyme include the following drug classes: tricyclic antidepressants, selective serotonin reuptake inhibitors, beta-blockers, antiarrhythmics class 1C (e.g., flecainide and propafenone) and monoamine oxidase inhibitors Type B. Co-administration of terbinafine should be done with careful monitoring and may require a reduction in dose of the 2D6-metabolized drug.

Terbinafine tablet and cream are contra-indicated in individuals with hypersensitive to terbinafine.

The adverse events reported encompass gastrointestinal symptoms (including diarrhea, dyspepsia and abdominal pain), liver test abnormalities, rashes, urticaria, pruritus, and taste disturbances. In general, the adverse events were mild, transient, and did not lead to discontinuation. Adverse events, based on worldwide experience with terbinafine use, include: idiosyncratic and symptomatic hepatic injury and more rarely, cases of liver failure, some leading to death or liver transplant, serious skin reactions, severe neutropenia, thrombocytopenia, angioedema and allergic reactions (including anaphylaxis). Other adverse reactions that have been reported include malaise, fatigue, vomiting, arthralgia, myalgia, and hair loss.

Terbinafine tablet: There are no adequate and well-controlled studies in pregnant women. Because animal reproduction studies are not always predictive of human response, and because treatment of onychomycosis can be postponed until after pregnancy is completed, it is recommended that terbinafine not be initiated during pregnancy. After oral administration, terbinafine is present in the breast milk of nursing mothers. Treatment with terbinafine is not recommended in nursing mothers.

Terbinafine cream: Foetal toxicity and fertility studies in animals suggest no adverse effects. There is no clinical experience with terbinafine in pregnant women; therefore, unless the potential benefits outweigh any potential risk, terbinafine should not be administered. Terbinafine is excreted in breast milk and therefore mothers should not receive terbinafine treatment whilst breast-feeding.

Warnings–

• Terbinafine tablets: Rare cases of liver failure, some leading to death or liver transplant, have occurred with the use of terbinafine tablets for the treatment of onychomycosis in individuals with and without preexisting liver disease. In the majority of liver cases reported in association with terbinafine use, the patients had serious underlying systemic conditions and an uncertain causal association with terbinafine. The severity of hepatic events and/or their outcome may be worse in patients with active or chronic liver disease. Treatment with terbinafine tablets should be discontinued if there is biochemical or clinical evidence of liver injury. There have been isolated reports of serious skin reaction (e.g., Stevens-Johnson Syndrome and toxic epidermal necrolysis). If progressive skin rash occurs, treatment with terbinafine should be discontinued.
• Terbinafine cream: Terbinafine cream is for external use only. Contact with the eyes should be avoided.

Precautions: Terbinafine are not recommended for patients with chronic or active liver disease. Before prescribing Terbinafine, pre-existing liver disease should be assessed. Hepatotoxicity may occur in patients with and without pre-existing liver disease. Pretreatment serum transaminase (ALT and AST) teste are advised for all patients before taking terbinafine tablets.

Pediatric use: The safety and efficacy of terbinafine have not been established in pediatric patients.

Use in the elderly: There is no evidence to suggest that elderly patients require different dosages or experience side-effects different to those of younger patients.

Clinical experience regarding overdose with terbinafine tablets is limited. Doses up to 5 gm (20 times the therapeutic daily dose) have been taken without inducing serious adverse reactions. The symptoms of overdose included nausea, vomiting, abdominal pain, dizziness, rash, frequent urination, and headache.

Other Antifungal preparations, Topical Antifungal preparations

Store in a cool and dry place, below 30°C, protect from light.