Terbifast

Uses

Terbifast cream is used for the treatment of the following dermatological infections: interdigital tinea pedis (Athlete’s foot), tinea cruris (jock itch) or tinea corporis (ring worm) due to susceptible organisms and planter tinea pedis (mocasin type) due to Trichophyton spp.

Terbifast tablet is used for the treatment of onychomycosis of the toe nail or finger nail due to dermatophytes and also by non-dermatophyte fungi.

Terbifast is also used to associated treatment for these conditions: Onychomycosis, Pityriasis versicolor, Sporotrichosis, Tinea Capitis, Tinea Corporis, Tinea Cruris, Tinea Pedis, Cutaneous candidiasis, Severe Tinea Corporis, Severe Tinea Cruris, Severe Tinea Pedis

How Terbifast works

Terbifast inhibits the enzyme squalene monooxygenase (also called squalene epoxidase), preventing the conversion of squalene to 2,3-oxydosqualene, a step in the synthesis of ergosterol. This inhibition leads to decreased ergosterol, which would normally be incorporated into the cell wall, and accumulation of squalene.

Generation of a large number of squalene containing vesicles in the cytoplasm may leach other lipids away from, and further weaken, the cell wall.

Dosage

Terbifast dosage

Topical application:

Terbifast cream to affected areas once or twice daily for 1-2 weeks may be adequate for fungal infections of the skin but certain infections may require oral Terbifast tablet therapy.Usual duration of treatment of Terbifast cream:

• In Tinea corporis and Tinea cruris: 1-2 weeks.
• In Tinea pedis: 2-4 weeks (One week of treatment will normally suffice if the cream is applied twice daily.).
• In Cutaneous candidiasis: 1-2 weeks
• In Pityriasis (tinea) versicolor: 2 weeks.

To prevent relapses in fungal infection, treatment should be continued for a adequate length of time. To apply Terbifast cream clean and dry the affected areas thoroughly and apply the cream once or twice a day to the affected skin and surrounding area in a thin layer and rub in lightly. In the case of intertriginous infections the application may be covered with a gauze strip, especially at night.

Oral administration:

Terbifast tablet is essential for hair or nail infections:

• The usual oral dose: Terbifast 250 mg daily for 2 to 12 weeks depending upon the infection.
• Finger nail onychomycosis: Terbifast 250 mg once daily for 6 weeks.
• Toe nail onychomycosis: Terbifast 250 mg once daily for 12 weeks.

Side Effects

Terbifast Tablet: Abdominal discomfort, anorexia, nausea, diarrhoea, headache, rash and urticaria occasionally with arthralgia or myalgia. Less frequently taste disturbance. Rarely liver toxicity, photosensitivity, serious skin reactions etc.

Terbifast Cream: Redness, itching, or stinging; rarely allergic reactions.

Toxicity

The subcutaneous LD₅₀ in rats and mice is >2g/kg. The TDLO for women is 210mg/kg/6W.

Overdose data with terbinafine is rare, however symptoms are expected to be nausea, vomiting, abdominal pain, dizziness, rash, frequent urination, and headache. Treat overdose with activated charcoal as well as symptomatic and supportive therapy.

Precaution

Terbifine cream is for external use only. Contact with eyes should be avoided.Good general hygiene is necessary in conjunction with the use of Terbifast in order to prevent reinfection (eg. from underwear, socks,shoes etc).

Terbifast tablet is 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) tests are advised for all patients before taking terbinafine tablets.

Interaction

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.

Food Interaction

• Limit caffeine intake. Terbifast may reduce the metabolism of caffeine by approximately 19%, monitor for increased effects of caffeine.
• Take with or without food.

Terbifast Drug Interaction

Moderate: amphetamine / dextroamphetamine, duloxetine, metoprololUnknown: aspirin, diphenhydramine, ubiquinone, omega-3 polyunsaturated fatty acids, escitalopram, atorvastatin, pregabalin, esomeprazole, montelukast, levothyroxine, acetaminophen, cyanocobalamin, ascorbic acid, ergocalciferol, cholecalciferol, alprazolam, cetirizine

Terbifast Disease Interaction

Major: liver disease, neutropeniaModerate: depression, immunosuppression, lupus, renal dysfunction

Volume of Distribution

A single 250mg oral dose of terbinafine has a volume of distribution at steady state of 947.5L or 16.6L/kg.

Elimination Route

Oral terbinafine is >70% absorbed but only 40% bioavailable after first pass metabolism, reaching a C_max of 1µg/mL with a T_max of 2 hours an an AUC of 4.56µg*h/mL. Over the course of a week, 1% topical terbinafine's C_max increases from 949-1049ng/cm²

Half Life

Oral terbinafine has an effective half life of approximately 36 hours. However, the terminal half life ranges from 200-400 hours as it distributes into skin and adipose tissue. 1% topical terbinafine's half life increases over the first seven days from approximately 10-40 hours.

Clearance

A single 250mg oral dose of terbinafine has a clearance of 76L/h or 1.11L/h/kg.

Elimination Route

Terbifast is approximately 80% eliminated in urine, while the remainder is eliminated in feces. The unmetabolized parent drug is not present in urine.

Pregnancy & Breastfeeding use

Terbifast 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 breast milk of nursing mothers. Treatment with terbinafine in not recommended in nursing mothers.

Terbifast 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. Terbifast is excreted in breast milk and therefore mothers should not receive terbinafine treatment whilst breast-feeding.

Contraindication

Hypersensitivity to Terbifast or any of the excipients in thepreparation

Special Warning

Use in Children: Terbifast cream appears to be an effective and well-tolerated treatmenr of tinea corposis and tinea cruris in children.

Use in Elderly: Terbifast appears to be safe in the elderly. The dose should be reduced by half if significant hepatic or renal impairment is present.

Acute Overdose

Clinical experience regarding overdose with terbinafine tablets is limited. Doses up to 5 grams (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.

Storage Condition

Store in a cool and dry place, protected from light.

Innovators Monograph

You find simplified version here Terbifast