Terbilab250 mg

Terbilab is an allylamine antifungal used to treat infections caused by dermatophyte fungi. Its indications can be classified by strength of evidence as follows:

Established / Approved Uses

• Onychomycosis (fungal nail infection): Oral Terbilab is indicated for the treatment of onychomycosis of the toenail or fingernail caused by dermatophytes (tinea unguium), confirmed by laboratory testing (KOH preparation or culture) where appropriate.
• Tinea pedis, tinea cruris, tinea corporis: Topical Terbilab (cream, gel, or spray) is indicated for superficial dermatophyte skin infections including athlete's foot, jock itch, and ringworm of the body. Oral Terbilab may also be used for more extensive or refractory cases.
• Tinea capitis (scalp ringworm): Oral Terbilab granules are indicated in pediatric patients for tinea capitis caused by susceptible dermatophytes.

Uses Requiring Clinical Judgment / Extent-Dependent

Choice between topical and oral Terbilab for tinea pedis, cruris, and corporis depends on the extent, severity, and site of infection, and response to prior topical therapy.

Off-Label Use

Terbilab is sometimes used off-label for other dermatophyte or selected non-dermatophyte fungal skin infections at a physician's discretion; such use should be guided by clinical assessment and, where possible, mycological confirmation.

Terbinafine is available in several formulations:

• Oral tablets containing Terbinafine hydrochloride equivalent to 250 mg Terbinafine base.
• Oral granules (sprinkle formulation) in single-dose packets, for pediatric use, providing Terbinafine hydrochloride equivalent to 125 mg or 187.5 mg Terbinafine base per packet.
• Topical preparations (1% cream, gel, or spray) containing Terbinafine hydrochloride equivalent to 1% Terbinafine base.

Exact strengths and available formulations may vary by brand; refer to the specific product label.

Terbilab is a synthetic allylamine-class antifungal agent used to treat fungal infections of the skin, hair, and nails caused by dermatophytes such as Trichophyton, Microsporum, and Epidermophyton species. Terbilab is fungicidal against dermatophytes and is available as oral tablets, oral granules, and topical preparations.

Terbilab works by selectively inhibiting a key enzyme in fungal cell membrane synthesis, leading to fungal cell death. It is widely used for the treatment of onychomycosis (fungal nail infection) and various forms of tinea (ringworm) infection.

Antifungal agent (Allylamine class) — Terbilab is a member of the allylamine antifungals, distinct from azole antifungals.

Terbinafine is an allylamine antifungal that acts by inhibiting fungal squalene epoxidase, an enzyme in the ergosterol biosynthesis pathway of the fungal cell membrane. This inhibition causes squalene to accumulate within the fungal cell while blocking ergosterol production.

The resulting ergosterol deficiency and intracellular squalene accumulation disrupt fungal cell membrane structure and function, leading to fungal cell death. This mechanism makes Terbinafine fungicidal against most dermatophytes, in contrast to the fungistatic action of many azole antifungals.

Terbinafine is well absorbed after oral administration, is highly lipophilic, and distributes into skin, nails, and hair, where it accumulates and persists for weeks after treatment is stopped, allowing shorter treatment courses. It is extensively metabolized in the liver (partly via CYP2D6, which it also inhibits) and excreted mainly in urine.

Terbilab oral tablets can be taken with or without food, at approximately the same time each day, and should be swallowed whole with water. Do not stop the course early even if the nail or skin appears to improve, since fungal eradication requires the full prescribed duration (see Precautions and Warnings).

Oral granules should be opened and sprinkled onto a spoonful of soft, non-acidic food (not fruit-based) and swallowed immediately without chewing.

Topical Terbilab should be applied to clean and dry skin only, in a thin layer covering the affected area and immediately surrounding skin, then rubbed in gently. Avoid contact with eyes, mouth, and mucous membranes, and avoid occlusive dressings unless directed by a physician.

Clinically significant drug interactions with Terbilab (oral) include:

• CYP2D6 substrates (tricyclic antidepressants, SSRIs, beta-blockers such as metoprolol, monoamine oxidase inhibitors type B, antiarrhythmics): Terbilab is a potent CYP2D6 inhibitor and can increase plasma levels of these drugs, raising the risk of toxicity; dose adjustment of the co-administered drug may be needed.
• Rifampin and other strong CYP inducers: can significantly reduce Terbilab plasma concentrations, potentially reducing efficacy.
• Cimetidine: can increase Terbilab plasma concentrations by inhibiting its metabolism.
• Hormonal contraceptives: rare reports of menstrual irregularities with concurrent oral Terbilab use; clinical significance is uncertain but should be monitored.
• Alcohol and other hepatotoxic drugs: concurrent use with oral Terbilab may increase the risk of liver injury (see Contraindications and Precautions and Warnings).

Inform the prescribing physician of all other medicines being taken before starting Terbilab.

Common side effects of Terbilab (mostly with oral use) include headache, gastrointestinal upset (diarrhea, dyspepsia, nausea, abdominal pain), and mild skin rash. Topical Terbilab may cause local irritation, burning, redness, or itching at the application site.

Less common but serious side effects include:

• Hepatotoxicity, including rare cases of liver failure requiring transplant or resulting in death (oral use) — see Precautions and Warnings.
• Taste and smell disturbance or loss, which may be prolonged or, rarely, permanent (oral use).
• Rare serious skin reactions, including Stevens-Johnson syndrome and toxic epidermal necrolysis.
• Rare blood dyscrasias (e.g., neutropenia, agranulocytosis) with prolonged oral use.
• Rare mood changes or depressive symptoms have been reported with oral use.

Patients should seek prompt medical attention for any severe rash, jaundice, dark urine, persistent nausea, or unusual bleeding/bruising.

Pregnancy: Data on the use of Terbilab in pregnant women are limited. Terbilab should be used during pregnancy only if clearly needed and the potential benefit justifies the potential risk to the fetus; oral Terbilab is generally avoided during pregnancy unless no suitable alternative exists. Consult a physician before use.

Lactation: Terbilab is excreted into breast milk. Use during breastfeeding is generally not recommended with oral therapy unless the expected benefit outweighs the potential risk to the infant; a physician should be consulted. Topical use should avoid application to the breast/nipple area if breastfeeding.

Antifungal treatment with Terbilab should always be completed for the full duration prescribed by the physician, even if symptoms improve earlier, to ensure complete eradication of the fungus and reduce the risk of relapse or resistance. Do not stop, extend, skip doses, or share this medicine with others without medical advice.

• Hepatotoxicity: Oral Terbilab has been associated with rare but serious liver injury, including liver failure. Baseline liver function testing is recommended before starting oral therapy for onychomycosis, especially for treatment courses longer than 6 weeks or in patients with pre-existing liver disease risk factors. Patients should be counseled to promptly report symptoms of liver dysfunction such as persistent nausea, loss of appetite, fatigue, jaundice (yellowing of skin/eyes), dark urine, or pale stools; Terbilab should be discontinued immediately if these occur.
• Taste and smell disturbance: Oral Terbilab may cause altered or lost taste and/or smell, which can occasionally be prolonged or permanent and may affect appetite and nutrition; report any such change to a physician.
• Serious skin reactions: Discontinue Terbilab immediately and seek medical attention if a progressive or severe skin rash, blistering, or mucosal lesions develop, as these may indicate Stevens-Johnson syndrome or toxic epidermal necrolysis.
• Blood dyscrasias: Rare cases of neutropenia and other blood disorders have occurred with prolonged oral use; periodic blood monitoring may be considered for extended courses.
• Renal/hepatic impairment: Use with caution; see Use in Special Populations.

Reports of Terbilab overdose are limited but may include headache, nausea, epigastric pain, dizziness, or rash. There is no specific antidote for Terbilab overdose.

If an overdose of Terbilab is suspected, seek immediate medical attention or contact a poison control center. Treatment is generally supportive and symptomatic; activated charcoal may be considered by a healthcare provider if given soon after ingestion. Do not attempt to manage a suspected overdose at home without medical guidance.

Store at room temperature (below 30°C), away from light and moisture. Keep out of reach of children.

• Renal impairment: Use of Terbilab in patients with creatinine clearance below 50 mL/min is not well studied and is generally not recommended unless the expected benefit outweighs the potential risk; if used, a physician may consider dose reduction and closer monitoring.
• Hepatic impairment: Oral Terbilab is contraindicated in patients with chronic or active liver disease (see Contraindications).
• Elderly: No specific dose adjustment is generally required based on age alone, but elderly patients may have a higher likelihood of concomitant hepatic or renal impairment or polypharmacy, warranting careful monitoring.
• Pediatric patients: Oral granules are approved for tinea capitis in children 4 years and older; safety and efficacy of oral tablets and topical formulations in children below certain ages have not been well established for all indications — see Pediatric Uses.

• Onychomycosis, toenail (oral): 12 weeks.
• Onychomycosis, fingernail (oral): 6 weeks.
• Tinea capitis, pediatric (oral granules): 6 weeks.
• Tinea pedis/cruris/corporis (topical): 1–4 weeks depending on the specific infection and product.
• Tinea pedis/cruris/corporis (oral, for extensive disease): typically 2–6 weeks per physician assessment.

The full prescribed duration of Terbilab therapy should always be completed, even if visible improvement occurs earlier.

Antifungals; Allylamines

Terbinafine exerts its antifungal effect by inhibiting squalene epoxidase, an enzyme required for the conversion of squalene to ergosterol in the fungal cell membrane synthesis pathway. Ergosterol is an essential structural component of fungal cell membranes.

By blocking this enzyme, Terbinafine causes a deficiency of ergosterol and an accumulation of squalene within the fungal cell. The resulting membrane disruption and toxic squalene accumulation lead to fungal cell death, making Terbinafine fungicidal against susceptible dermatophytes, unlike the fungistatic azole antifungals which act at a later step of the same pathway.

B

Oral Terbilab granules are approved for the treatment of tinea capitis in pediatric patients 4 years of age and older, dosed by body weight once daily for 6 weeks:

Safety and efficacy of oral Terbilab tablets for onychomycosis in children have not been well established, and use in this age group for that indication is generally not recommended unless specifically directed by a physician. Safety and efficacy of topical Terbilab in young children (typically below 12 years, depending on the product) have also not been fully established for all products; use should be guided by a physician's advice.