Terbinafine 250 mg Tablets (Terbinafine Hydrochloride)

Terbinafine is a systemic antifungal in the allylamine class. It works by inhibiting fungal squalene epoxidase, an enzyme needed for ergosterol synthesis in the fungal cell membrane. This causes toxic buildup of squalene and cell death. After an oral dose, terbinafine distributes into skin, hair and nails at fungicidal levels (detectable in nail for weeks after stopping). The 250 mg tablet is a prescription-only oral formulation (often marketed as Lamisil and generics) used for deep or hard-to-treat dermatophyte infections. (Terbinafine also exists as OTC topical creams/gels for athlete’s foot and ringworm, but the tablet is reserved for severe or nail infections that require systemic therapy.)

Uses (Indications)

Terbinafine tablets are indicated for dermatophyte fungal infections, especially:

• Onychomycosis (nail fungus) – Most commonly used for toenail or fingernail infections caused by dermatophytes (e.g. Trichophyton rubrum). Oral terbinafine typically offers higher cure rates than oral azole antifungals in nail disease. It’s approved for fingernail fungus (6 weeks of therapy) and toenail fungus (12 weeks).
• Tinea capitis (scalp ringworm) – An oral antifungal is required for scalp infections. Terbinafine (250 mg/day for ~6–8 weeks, weight-based in children) is effective against Trichophyton scalp infections and is often as good as griseofulvin.
• Cutaneous dermatophyte infections – It can treat severe or widespread tinea corporis (body), tinea cruris (jock itch), and tinea pedis (athlete’s foot), especially when topical therapy fails or infection is extensive. (For localized skin tinea, topical antifungals are usually first-line, but terbinafine tablets may be used for extensive or refractory cases.)
• Miscellaneous – Terbinafine also treats Malassezia (pityriasis) and some yeast infections (e.g. Candida) off-label, though it is not reliable for Candida fingernail infections. It is not effective for systemic fungal infections.

In short, terbinafine tablets are prescribed for persistent dermatophyte infections of nails and (less commonly) skin or scalp that require systemic therapy. Compared to azole antifungals, terbinafine is often preferred for nail fungus due to its fungicidal activity and tissue penetration.

Dosage and Administration

• Adults: The usual dose is 250 mg once daily by mouth (with a glass of water). Tablets may be taken with or without food.
• Nail infections (onychomycosis): Typical courses are 6 weeks for fingernail infections or 12 weeks for toenail infections. (Sustained cure occurs only after the nail regrows, so clinical benefit may appear months after treatment.) Therapy is sometimes extended or repeated if needed.
• Scalp infection (tinea capitis): 250 mg once daily for ~6 weeks (children’s dose based on weight, typically 125–250 mg/day). (Capitis requires oral therapy; terbinfine is an alternative to griseofulvin.)
• Skin infections: Generally shorter courses (often 2–4 weeks) are sufficient. For example, general tinea corporis is often treated ~4 weeks, tinea cruris (groin) ~2–4 weeks, and tinea pedis (feet) ~2–6 weeks. Duration varies by severity and site.
• Special populations: In severe renal impairment (CrCl ≤50 mL/min), a reduced dose (e.g. 125 mg once daily) may be used. No adjustment is usually needed for mild renal dysfunction. Terbinafine is not recommended for patients with significant liver disease.

Administration tips: Swallow the tablet whole with water. (A granule formulation is available for children <18 years). Complete the full prescribed course even if symptoms improve, to ensure eradication. Follow-up (e.g. nail evaluation) is usually done weeks to months after therapy.

Side Effects and Safety

Terbinafine is generally well tolerated, but patients should be aware of common side effects and rare serious reactions.

• Common adverse effects: Gastrointestinal symptoms (e.g. nausea, dyspepsia, diarrhea) and headache are frequent. Other common effects include skin reactions (rash, itching) and mild fatigue. A notorious side effect is taste disturbance (dysgeusia) – some patients experience reduced or altered taste (and sometimes smell) that usually resolves weeks after stopping, but can be prolonged. (On rare occasion taste loss has led to weight loss if severe.) Mild dizziness or vertigo is also reported.

• Rare but serious effects: Hepatotoxicity is the most concerning. Terbinafine can cause liver enzyme elevations and, very rarely, severe cholestatic hepatitis or liver failure. Cases of fatal or life-threatening liver injury have been reported, often in patients with other health issues. For this reason, terbinafine is usually avoided in anyone with preexisting chronic liver disease; baseline liver function tests (AST/ALT) are recommended, and therapy should be stopped if any signs of hepatic injury occur (e.g. dark urine, jaundice, persistent nausea).

  Blood cell abnormalities are uncommon but documented. Transient lymphocyte drops, neutropenia or thrombocytopenia have occurred. Rare reports of agranulocytosis or pancytopenia have emerged; patients on long courses (>6 weeks) may have periodic blood counts checked. Terbinafine has also been reported to trigger or worsen systemic or cutaneous lupus erythematosus in rare cases, and very rarely severe skin reactions (Stevens-Johnson syndrome/toxic epidermal necrolysis) have been reported.

• Other effects: Allergic reactions (hives, angioedema, anaphylaxis) are possible in sensitive individuals. Patients have reported changes in vision (blurry or altered color perception) in isolated cases. Hepatic or renal dosing changes may be needed in elderly or organ-impaired patients.

If any severe adverse signs appear during treatment — especially symptoms of liver inflammation (jaundice, dark urine), unexplained fever/rash/swollen lymph nodes, or major mood changes — discontinue terbinafine and seek medical care. Discuss any troublesome side effects with your doctor.

Precautions and Interactions

• Liver and blood monitoring: Because of rare hepatotoxicity, liver enzymes should be checked before starting therapy and monitored during prolonged treatment. Do not prescribe if AST/ALT are elevated or if active liver disease is present. If signs of liver injury occur, stop the drug immediately. Patients with neutropenia or immunodeficiency should have periodic CBCs if on long-term terbinafine.

• Drug interactions: Terbinafine is metabolized by and moderately inhibits CYP450 enzymes (especially CYP2D6) in the liver. This can raise blood levels of certain medications. For example, terbinafine can increase levels of some anti‐arrhythmic drugs and antidepressants (tricyclics, SSRIs, MAO inhibitors) that are CYP2D6 substrates. Notably, it has been shown to increase desipramine levels and can interact with beta-blockers. Conversely, enzyme inducers like rifampin can lower terbinafine levels, while enzyme inhibitors like cimetidine can raise it. Always tell your doctor all medications (prescription, OTC, supplements) you take.

• Blood thinners / others: Terbinafine has minimal effect on CYP2C9 or 1A2, so it generally does not significantly alter warfarin or theophylline levels. However, vitamin K levels should still be monitored if on warfarin. Contraceptive pills may be slightly less reliable; irregular menstrual bleeding has been reported.

• Pregnancy and lactation: Terbinafine is Pregnancy Category B. It is usually avoided during pregnancy unless clearly needed, and breastfeeding is not recommended while on terbinafine. Discuss risks vs. benefits with your physician if pregnant or nursing.

• Children: Oral terbinafine tablets are not approved for children <18 years (for those patients, use pediatric granule formulations or alternative antifungals).

• Other precautions: Patients with psoriasis or connective tissue disease should use terbinafine cautiously. If manifestations of lupus or severe connective tissue reaction appear, discontinue treatment. Avoid alcohol use during therapy if possible (to reduce liver stress). Terbinafine can cause dizziness or drowsiness in some people; they should not drive or operate machinery if affected.

Terbinafine 250 mg tablets are a potent systemic antifungal reserved for confirmed dermatophyte infections of skin, hair or nails. The typical adult dose is one 250 mg tablet daily. For nail fungus, course lengths are months (6 weeks for fingers, 12 or more for toes). Shorter courses (2–6 weeks) treat athlete’s foot or jock itch as directed. The drug is fungicidal and highly effective against Trichophyton species. Its main benefits are clearing persistent fungal infections and improving nail quality.

Most patients handle terbinafine well, but liver function must be monitored. Common side effects include GI upset and headache; uncommon but serious risks include liver toxicity, blood count changes, and allergic reactions. Drug interactions (especially with CYP2D6 substrates) are possible. Always inform your healthcare provider of all conditions and medications before using terbinafine.

Note: Terbinafine is a prescription medication. This summary is for educational purposes only and does not replace professional medical advice. Follow your doctor’s instructions and the product label for safe use.