Lamisil: Uses, dosage, side effects, warnings & patient reviews

What is Lamisil (Terbinafine)?

Lamisil is the brand name for the antifungal medication terbinafine. It belongs to the allylamine class of antifungals within the broader anti-fungal drug category. Terbinafine works by inhibiting a key enzyme (squalene epoxidase) in fungal cell membranes, leading to a deficiency of ergosterol and accumulation of squalene, which results in fungal cell death.

This fungicidal action makes it effective against dermatophytes, the fungi most commonly responsible for skin and nail infections.

Available Forms

• Lamisil Tablets: Prescription-only oral tablets, typically 250 mg.
• Lamisil Cream/Lamisil AT: Over-the-counter topical antifungal cream, gel, or spray used for skin infections and often included in general skincare regimens for fungal conditions.

How to Take Lamisil

Administration instructions differ significantly between oral and topical formulations. It is critical to use the medication exactly as prescribed by a healthcare provider and for the full duration of treatment, even if symptoms improve earlier.

Oral Tablets (Lamisil)

Lamisil tablets should be swallowed whole with water. They can be taken with or without food. For the treatment of toenail fungus, the typical course is one 250 mg tablet daily for 12 weeks. For fingernail fungus, the course is typically 6 weeks. Do not stop treatment early without consulting your doctor, as this can lead to treatment failure and recurrence of the infection.

Topical Creams/Sprays (Lamisil AT)

Topical terbinafine is applied directly to the affected and surrounding clean, dry skin areas, usually once or twice daily as directed. It is important to wash hands before and after application. Treatment duration for skin infections like athlete’s foot is typically 1 to 2 weeks, and may continue for 1 to 2 weeks after symptoms clear to prevent recurrence.

Side Effects of Lamisil

Side effect profiles differ between oral and topical terbinafine. Oral administration is associated with more systemic side effects, while topical use typically causes only local reactions.

Note: Topical formulations have minimal systemic absorption and therefore a lower risk of the serious side effects listed for oral therapy.

What is Lamisil Used For?

Lamisil (terbinafine) is indicated for the treatment of infections caused by susceptible fungi (dermatophytes). Its use is dictated by the formulation.

Oral Lamisil Tablets (Prescription)

• Onychomycosis: Treatment of fungal infections of the toenails or fingernails (lamisil for toenail fungus, lamisil for nail fungus).

Topical Lamisil AT (Over-the-Counter)

• Tinea pedis: Treatment of athlete’s foot.
• Tinea cruris: Treatment of jock itch.
• Tinea corporis: Treatment of ringworm.
• Treatment of other superficial dermatophyte infections, which are types of uncomplicated skin and skin structure infections.

Important Safety Concerns and Considerations

Hepatotoxicity (Liver Damage)

Oral terbinafine has been associated with rare cases of serious liver failure, sometimes requiring transplant or leading to death. This can occur in patients with and without pre-existing liver disease. Symptoms may resemble those of hepatitis, including nausea, fatigue, jaundice, and dark urine. Baseline liver function tests (LFTs) are recommended before starting oral therapy, and treatment should be discontinued if biochemical evidence of liver injury develops.

Taste and Smell Disturbance

A partial or complete loss of taste (ageusia or dysgeusia) is a relatively common side effect of oral terbinafine. It is usually reversible upon discontinuation but can persist for months or, in rare cases, be permanent. This can affect nutrition and oral health, relating to issues of oral cavity health.

Serious Skin Reactions and Psoriasis

Severe cutaneous adverse reactions (SCARs), including Stevens-Johnson Syndrome and toxic epidermal necrolysis, have been reported. Terbinafine may also induce or exacerbate pre-existing psoriasis or cause psoriasiform eruptions. The drug should be discontinued if a progressive skin rash develops.

Hematologic Effects

Rare cases of neutropenia (low white blood cells), including agranulocytosis, have been reported. This can increase susceptibility to serious infections, potentially progressing to conditions like septicemia. Patients should be advised to report any signs of infection, such as fever or sore throat.

Depressive Symptoms

Depression, anxiety, and other mood changes have been reported during post-marketing surveillance of oral terbinafine use. Patients should be monitored for changes in mood or behavior. More information can be found in the depression drug category resources.

Critical Warnings for Lamisil Use

Liver Function Monitoring

Baseline liver enzyme tests (ALT, AST) are recommended for all patients prior to initiating oral Lamisil therapy. Healthcare providers should consider monitoring in patients taking terbinafine for more than six weeks. Therapy should be immediately discontinued if symptomatic or biochemical evidence of liver injury occurs.

Contraindication in Chronic or Active Liver Disease

Oral Lamisil is contraindicated in patients with chronic or active liver disease. The risk of severe hepatotoxicity outweighs the potential benefit in this population.

Management of Skin Rash

If a progressive skin rash occurs, which may be indicative of a severe cutaneous adverse reaction, terbinafine should be discontinued immediately and medical attention sought.

Monitoring in Patients with Immunodeficiency

In patients with known or suspected immunodeficiency, complete blood count (CBC) monitoring should be considered if treatment with oral terbinafine exceeds six weeks due to the potential risk of blood dyscrasias.

Lamisil Dosage Information

Dosage must be individualized by a healthcare provider based on infection type, patient factors, and formulation. The following are standard guidelines.

Important Administration Notes

• Renal/Hepatic Impairment: Patients with renal impairment (creatinine clearance ≤50 mL/min) or hepatic cirrhosis should not receive the standard oral dose. A reduced dose of 250 mg every other day is recommended.
• Consistency: For both oral and topical therapy, consistent daily use for the full prescribed duration is critical for efficacy and to prevent recurrence.

Drug Interactions with Lamisil

Oral terbinafine is a potent inhibitor of the cytochrome P450 enzyme CYP2D6 and a minor substrate/inhibitor of CYP2C9 and CYP3A4. This is the basis for its most significant interactions.

Additional Information

Storage and Handling

Store oral tablets at room temperature (20°C to 25°C / 68°F to 77°F) in a tightly closed container, away from light and moisture. Topical creams and sprays should also be stored at room temperature. Keep all medications out of the reach of children and pets.

Historical Fact

Terbinafine was first synthesized in the late 1970s and introduced for medical use in the early 1990s. Its development represented a significant advancement in antifungal therapy due to its fungicidal (killing) mechanism against dermatophytes, compared to the fungistatic (growth-inhibiting) action of the previously dominant azole class of drugs. This property contributed to its high cure rates for nail fungus.

References and Medical Sources

1. U.S. Food and Drug Administration (FDA). Lamisil (terbinafine hydrochloride) Tablets Prescribing Information. [Revised 2023]. https://www.accessdata.fda.gov/drugsatfda_docs/label/2012/020539s021lbl.pdf
2. MedlinePlus. Terbinafine. U.S. National Library of Medicine. [Updated 2022]. https://medlineplus.gov/druginfo/meds/a699061.html
3. Gupta, A.K., et al. “The use of terbinafine in the treatment of onychomycosis in adults and special populations: A review of the evidence.” Journal of the American Academy of Dermatology. 2021.
4. Drugs.com. Terbinafine Professional Monograph. [Updated 2024]. https://www.drugs.com/monograph/terbinafine.html

This information is for educational purposes and is not a substitute for professional medical advice. Always consult your healthcare provider for diagnosis and treatment.

Disclaimer: The information on this site is provided for informational purposes only and is not medical advice. It does not replace professional medical consultation, diagnosis, or treatment. Do not self-medicate based on the information presented on this site. Always consult with a doctor or other qualified healthcare professional before making any decisions about your health.