Lamisil

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Lamisil

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Medically reviewed

Laura Arias

Last updated on 22/12/2025

This page provides general, reference-level information compiled from official medical sources. It is not a substitute for professional medical advice, diagnosis, or treatment. For decisions about your health, please consult a qualified healthcare professional.

Overview of Lamisil

Quick Facts

Property Description
Active ingredient Terbinafine Hydrochloride
Form Tablet, Cream, Gel, Solution, Spray, Granules
Pharmacological class Allylamine Antifungal Agent
Common purpose Elimination of fungal infections
Origin Synthetic compound

The Definitive Identity of Lamisil (Terbinafine)

Lamisil is the widely recognized trade name for a medicinal product containing the active ingredient Terbinafine Hydrochloride, a synthetic chemical compound. This substance is formally classified as an Antifungal agent and belongs to the Allylamine pharmacological class. This identity confirms its sole, general purpose: to target and eliminate fungal microorganisms. Lamisil, as a brand, is particularly associated with treatments for dermatophytosis, an application that is clinically recognized and supported by pharmacological studies. The medicinal product is available in both prescription (Rx) tablets for internal infections and over-the-counter (OTC) topical forms for localized skin issues, defining a key difference in its availability and therapeutic scope.

What Class of Medicine is Terbinafine and How Does It Function?

Terbinafine, as an Allylamine antifungal, is distinguished by a mechanism that results in a potent fungicidal action, meaning it actively kills fungal cells rather than merely halting their growth. Its primary function is to target and inhibit the fungal enzyme squalene epoxidase, an essential step in the process the fungus uses to construct its cell membrane. By interrupting this process, the medicine causes toxic levels of a substance called squalene to build up inside the fungal cell, leading directly to the pathogen’s death. This mechanism of action, which is distinct from many other antifungal types, underscores its general purpose as a highly effective tool for clearing fungal populations.

Available Forms of Lamisil: Topical and Oral Preparations

The medicine is manufactured in various dosage forms to match the required administration route, facilitating effective treatment delivery tailored to the infection's location. The preparations include tablets and granules for oral (systemic) administration, which allows the active ingredient to enter the bloodstream for generalized or internal infections. Conversely, creams, gels, solutions, and sprays are formulated as topical preparations, designed for direct application to the skin to manage localized, superficial fungal conditions. This broad range of forms offers versatility in treating conditions from the internal nail bed to the surface of the skin.

What side effects are possible with Lamisil?

Possible side effects and safety information

The official regulatory documentation for oral Terbinafine Hydrochloride (Lamisil) systematically classifies a range of potential adverse reactions, grouped according to the physiological system or organ class affected, and assigned frequency categories based on regulatory standards. The safety profile includes both frequently reported and rare but serious systemic effects.

Documented Frequency Classifications

Adverse events are often observed within specific System Organ Classes (SOC). The highest documented frequency categories include:

  • Very Common (affecting 1/10 patients): Reactions often involve the musculoskeletal, nervous, and gastrointestinal systems. Specific effects listed are headache, general musculoskeletal reactions (arthralgia, myalgia), and various gastrointestinal symptoms (abdominal distension, nausea, diarrhea).
  • Common (affecting 1/100 to <1/10 patients): Reactions in this tier include decreased appetite, dysgeusia (disturbance of taste), and an increase of hepatic enzymes.

Serious Adverse Reactions and Safety Constraints

Post-marketing reports and regulatory documents note rare but serious systemic effects, including severe hepatic failure, which has been documented to require liver transplant or result in death. Other serious reactions include severe and potentially life-threatening dermatological events such as Stevens-Johnson syndrome (SJS) and Toxic Epidermal Necrolysis (TEN), as well as rare blood disorders (e.g., neutropenia).

Specific safety considerations are documented for certain populations: Oral Terbinafine is contraindicated in individuals with chronic or active hepatic disease. It is not recommended for use in patients with renal impairment or in the pediatric population due to limited data. Furthermore, the label notes that taste and smell disturbances may, in rare cases, be permanent.

Overdose and Emergency Response

Overdose Manifestations and Required Emergency Actions

The official regulatory profile for acute overdose following supratherapeutic ingestion of oral Lamisil (terbinafine) documents a predictable range of symptoms. These documented manifestations commonly include headache, dizziness, nausea, vomiting, and epigastric or stomach pain. The accidental ingestion of topical formulations is also documented to result in a similar clinical presentation.

Regulatory authorities mandate specific actions due to the risk of severe systemic outcomes. Immediate medical attention is required upon observing signs of organ toxicity. These critical indicators include persistent nausea, anorexia, fatigue, jaundice, dark urine, or upper abdominal pain, which are documented signs of potential liver injury. Other severe outcomes requiring immediate action and drug discontinuation include severe neutropenia and serious skin reactions such as Stevens-Johnson Syndrome.

Supportive Management Protocol

Official prescribing information states that no specific antidote is known for Terbinafine overdose. Management is restricted to supportive and symptomatic treatment. Procedures are focused on the elimination of the active ingredient from the gastrointestinal tract, typically by the administration of activated charcoal.

Therapeutic Uses of Lamisil

What Lamisil Treats: Main Uses and Benefits

Lamisil is commonly used for infections affecting the nails and scalp, which are often conditions presenting with systemic or localized discomfort and are caused by dermatophytes. This approach is relevant for infections presenting with noticeable nail thickness, discoloration, and structural changes. The primary benefit is to address the underlying fungal cause, which supports the long-term regrowth and improved appearance of nail and hair tissue.

The medication is used to help address widespread or persistent fungal skin conditions, including severe athlete's foot (tinea pedis), jock itch (tinea cruris), and ringworm (tinea corporis), that may require additional symptomatic support beyond topical options. The topical forms help manage symptoms related to inflammatory or irritative states like scaling, redness, and itching associated with common superficial infections. This assists with maintaining functional stability and contributes to easing the overall burden of these distressing cutaneous manifestations.


Quick Fact: Symptom Support Focus Lamisil is commonly used to help manage symptom clusters that may become intense or disruptive, focusing on easing the physical discomfort associated with persistent fungal infections.


Brief Listing of Indications

Lamisil is applied across therapeutic domains involving acute or disruptive symptom patterns, used to address conditions such as fungal infections of the nails (onychomycosis), ringworm of the body and groin, and specific fungal scalp infections (tinea capitis).

Regulatory References

  1. NIH MedlinePlus overview

Eligibility and Restrictions for Use

Lamisil (terbinafine) eligibility is strictly defined by government regulatory agencies based on pre-existing health status and patient demographics.

Populations for Whom Use is Prohibited or Restricted

Contraindications (Must Not Use):

  • Chronic or Active Liver Disease: The oral tablet is contraindicated due to the risk of hepatotoxicity.
  • Hypersensitivity: Individuals with a history of allergic reaction to terbinafine or any of the tablet's excipients.

Use Not Recommended or Restricted:

  • Renal Impairment: Not recommended for patients with moderate-to-severe kidney impairment ( creatinine clearance < 50 mL/min), as use is not adequately studied in this population.
  • Lactation (Breastfeeding): Use is contraindicated as terbinafine is excreted into breast milk.
  • Pregnancy: Not recommended due to limited clinical experience; should only be used if the potential benefit justifies the risk.

Age-Group Eligibility:

  • Adults are the standard population for use. Older adults may use the medicine, but pre-existing organ function should be considered.
  • Pediatric Use: Safety and efficacy have not been established for all adult indications in children; specific approvals (such as for tinea capitis) exist only in certain regions and age groups.

Comorbidity Cautions:

  • The medicine should be used with caution in patients with pre-existing Psoriasis or Lupus Erythematosus, as regulatory documents note it may exacerbate these conditions.

What should I know about interactions with other medicines?

Lamisil (terbinafine) can affect the metabolism of other medicinal products, leading to a change in plasma concentrations that may require dose adjustment or alternative therapy. The primary mechanism of interaction is the inhibition of the Cytochrome P450 2D6 (CYP2D6) enzyme.

Interacting Medicinal Products and Classes:

  • CYP2D6 Substrates: Lamisil can significantly increase the concentration of drugs predominantly metabolized by CYP2D6. This includes certain antidepressants (e.g., desipramine), beta-blockers, antiarrhythmics (Class 1C), and selective serotonin reuptake inhibitors (SSRIs). Co-administration with such products generally requires careful monitoring and often a dose reduction of the co-administered drug.
  • CYP Enzyme Inhibitors: Drugs that inhibit multiple Cytochrome P450 enzymes can increase Lamisil's concentration in the body. For instance, cimetidine and fluconazole are known to increase terbinafine exposure.
  • CYP Enzyme Inducers: Drugs that increase the activity of Cytochrome P450 enzymes can decrease Lamisil's concentration. Rifampicin significantly accelerates terbinafine clearance, potentially reducing its effectiveness.
  • Other Interactions: Terbinafine may decrease the plasma concentration of cyclosporine, an immunosuppressant. Cases of menstrual irregularities have also been reported with the concomitant use of Lamisil tablets and oral contraceptives.

Restriction: The product is not recommended for use with pimozide or ranolazine.

Mechanism of Action

How Lamisil Works: The Mechanism of Action

Selective Inhibition of the Fungal Squalene Epoxidase

The drug's action is defined by the selective non-competitive inhibition of the fungal enzyme squalene epoxidase (SE). This enzyme is critical for the ergosterol biosynthesis pathway, the metabolic process utilized by the fungus to assemble its cell membrane. By binding to SE, the drug initiates a mechanistic cascade that fundamentally alters the pathogen's structure.


The Cascade of Cell Membrane Disruption

Inhibition of the enzyme causes a severe shortage of ergosterol (the essential fungal sterol) while simultaneously causing a toxic buildup of its precursor, squalene, inside the fungal cell. This dual molecular action causes structural damage, increased permeability, and results in the lysis and death of the fungal cell. This direct fungicidal action is the primary resulting physiological effect of the mechanism.


Mechanism Selectivity and Fungal Potency Constraints

The mechanism exhibits selectivity for the target enzyme (SE) because it is unique to the fungal cell, showing minimal interaction with analogous human enzymes. However, this selectivity also dictates the mechanism's constraints: its fungicidal action is more pronounced against dermatophytes, whereas its action against other fungal types, such as certain yeasts, may be less effective or merely fungistatic (growth-inhibiting).

Dosage and Administration Information

Lamisil is administered via two primary routes: the oral route using 250 mg tablets or granules for systemic treatment, and the topical route using various creams and solutions for localized superficial fungal conditions. The official usage pattern for the oral tablet is based on a fixed 250 mg dose taken once daily. This consistent frequency is essential for maintaining drug levels throughout the therapeutic course.

Official Course Duration

The treatment length is strictly defined by the site of infection. For adults undergoing systemic therapy, fungal infections of the fingernails are typically addressed over a course of six weeks, while infections affecting the toenails require a longer course of twelve weeks. The pediatric granule formulation for tinea capitis is generally administered for six weeks, with the dose determined by the patient’s body weight.

Administration Context

The context of intake varies based on the formulation:

Usage Instruction Contextual Rule
Oral Tablets May be taken with or without food.
Oral Granules Must be administered with a meal; requires mixing with soft, non-acidic food and swallowing without chewing.

High-level constraints define the usage parameters for certain patient groups. For instance, the standard regimen is not recommended in patients with a creatinine clearance below 50 mL/min. If a dose is missed, it should be taken as soon as remembered, unless the next scheduled dose is near, in which case the missed dose is omitted to continue the daily schedule.

Recent Clinical Evidence

Research Evidence / Overview of Studies for Lamisil (Terbinafine)

This overview summarizes the structure of the clinical research that government regulators and scientific bodies use to evaluate the systemic (oral tablet) and topical forms of Lamisil (Terbinafine). This information describes the types of studies conducted, the outcomes they monitored, and the areas where research is still emerging.


Evidence Base for Oral Treatment: Fungal Nail Infections (Onychomycosis)

The evaluation of oral Terbinafine for fungal infections of the nails has been conducted through multiple Randomized Controlled Trials (RCTs) and subsequent Systematic Reviews and Meta-analyses.

  • Research examined outcomes using two key measures: mycological cure (lab confirmation of fungal clearance) and clinical cure (the complete or near-complete regrowth of a normal-appearing nail).
  • Findings described patterns observed in the studies regarding the percentage of patients evaluated at the end of the follow-up period who met the criteria for both mycological and clinical cure.

One limitation is that the assessment of the clinical cure is based on visual observation, meaning there may be some subjectivity in how the outcome is measured across different research settings.


Evidence Base for Oral Treatment: Fungal Scalp Infections (Tinea Capitis)

Research for Tinea Capitis primarily involves Randomized Trials that was evaluated in comparison to other established treatments.

  • This evidence base focuses on children, as Tinea Capitis is predominantly a pediatric infection. Trials evaluated outcomes related to mycological cure and clinical cure (resolution of symptoms like scaling and hair loss).
  • Studies reported how outcomes evolved and indicated that the findings may vary depending on the specific type of fungus causing the infection, with different patterns observed for infections caused by Trichophyton species compared to Microsporum species.

Durability of Response and Long-Term Follow-up

For long-term systemic treatment, particularly for onychomycosis, clinical research extends well past the active treatment period to assess the durability of the outcome and the likelihood of the infection returning.

A five-year prospective follow-up study specifically tracked patients after treatment for toenail onychomycosis, monitoring them for signs of infection return. The slow growth of the nail means the full effect of treatment may not be visible for many months; therefore, extended observation was required in trials.

Frequently Asked Questions (FAQ)

Common questions about Lamisil (FAQ)

Q: What kind of infections does the Lamisil tablet treat?

Official product information indicates that the oral tablet is primarily used to treat fungal infections of the nails (onychomycosis) caused by dermatophytes. It is also approved for tinea capitis (scalp ringworm) and severe cases of tinea corporis, tinea cruris, and tinea pedis where systemic (oral) treatment is considered appropriate due to the severity or extent of the infection.


Q: What should I do if my skin turns yellow while using Lamisil?

Regulatory documents state that yellowing of the skin or eyes (jaundice) is a potential sign of serious liver injury. Official guidance describes jaundice as a serious sign that requires immediate medical review and may necessitate discontinuation of the medication.


Q: Can Lamisil be used to treat yeast infections?

While the medicine is mostly recognized for treating dermatophyte infections (like ringworm), official product information also lists its use for cutaneous candidiasis (yeast infections of the skin). This may be used in cases where the severity or location of the yeast infection makes oral therapy a suitable option.


Q: Is Lamisil treatment necessary if the infection is only on the surface of the skin?

The oral tablet is generally reserved for infections of the skin where the site, severity, or widespread nature of the infection suggests that a systemic treatment (one that works throughout the body) is the appropriate choice. Topical creams and solutions are often used for superficial and localized skin infections.


Q: What research evidence supports the use of Lamisil for ringworm?

The oral medication is formally indicated for tinea corporis (ringworm of the body), tinea cruris (jock itch), and tinea capitis (scalp ringworm). Evidence from clinical studies supports various treatment durations for these specific dermatophyte infections based on the affected site.


Q: What is the difference between Lamisil and prescription antifungal nail lacquers?

Lamisil oral tablets provide systemic treatment, meaning the active ingredient enters the bloodstream to treat infections deep within the nail bed or body. Prescription nail lacquers, in contrast, are topical medicines that are applied directly to the nail surface to treat the localized infection.


Q: Does Lamisil stop working if you take it inconsistently?

Official product information indicates that irregular use or stopping treatment too early, even if symptoms appear to be better, carries the risk of the fungal infection recurring. Completing the full course is described in official documents as important to reduce the risk of the fungal infection returning.


Q: What are the signs of a serious allergic reaction to Lamisil?

Regulatory safety documents note that serious skin and hypersensitivity reactions have been reported, including the rare but severe Stevens-Johnson Syndrome (SJS). Serious allergic reactions are documented, and signs such as swelling (angioedema) or severe dermatological events have been reported in official safety information.


Q: What is the general success rate described in studies for Lamisil in treating toenail fungus?

Clinical trials for toenail fungus typically evaluate success using two key measures: mycological cure (clearance of the fungus) and clinical cure (regrowth of a healthy nail). Studies report success rates that vary based on the specific trial methodology, and these findings are used by regulators to evaluate the drug's intended purpose.


Q: What is the maximum recommended treatment time for Lamisil?

For systemic therapy with the oral tablet, the treatment duration is strictly defined by the infection site. According to official guidelines, the maximum recommended duration for common toenail onychomycosis is 12 weeks.


Q: How long does it typically take to see any kind of change after starting Lamisil?

For fungal skin infections, patients typically experience relief of clinical symptoms within a few days of starting treatment. For nail infections, the full clinical effect—the complete regrowth of a healthy nail—is only fully visible some months after the treatment course has ended, due to the slow nature of nail growth.


Q: Can I take pain relievers like Tylenol or Advil while I'm on Lamisil?

Based on official drug interaction information, Lamisil oral tablets are not currently known to interact with common, over-the-counter pain relievers such as paracetamol (Tylenol) or ibuprofen (Advil).


Q: How long does Lamisil stay in your system after you stop taking it?

Official pharmacokinetic information indicates that while the medicine is absorbed quickly, it remains in the system for a longer period. The terminal half-life of elimination, which shows how long it takes the body to fully clear the medicine, is approximately three weeks.


Q: Does Lamisil interact with caffeine?

The active ingredient in Lamisil can affect the enzyme responsible for metabolizing (breaking down) caffeine. This means that concurrent use could potentially lead to increased concentrations of caffeine in the body.


Q: Why do some people need blood tests while taking Lamisil?

Periodic monitoring of liver function tests is a standard recommendation, especially during the first few weeks of treatment. This monitoring is associated with the rare risk of liver injury, which is a documented adverse effect of the oral tablets.


Q: Are generic versions of Lamisil equally effective?

The FDA and other government agencies require that generic products meet strict regulatory standards for quality, strength, and performance. This means that generic versions containing the active ingredient terbinafine must demonstrate bioequivalence (act the same way in the body) as the brand-name product.


Q: Can I drink alcohol moderately while taking Lamisil?

Official regulatory guidance does not prohibit alcohol use with this medicine. However, because the medicine is primarily processed by the liver and carries a rare risk of hepatotoxicity (liver damage), the documented risk of liver problems is a factor for consideration when consuming alcohol.


Q: Are there any known interactions between Lamisil and herbal supplements?

Official drug interaction sources state that there is not enough regulatory-style testing to confirm the safety of taking complementary medicines, herbal remedies, and supplements with the tablets. This means potential interactions are not well-documented in product information.


Q: How does Lamisil affect my immune system?

The official product label notes reports of rare and usually reversible blood disorders, such as neutropenia (a low white blood cell count). This type of reaction may necessitate monitoring of blood counts if treatment is continued for an extended period.


Q: Why is it important to complete the full course of Lamisil even if symptoms improve?

It is important to complete the entire course prescribed because stopping treatment prematurely, even if the infection symptoms seem to have cleared up, carries a substantial risk of the fungal infection returning. Completing the full course is important to reduce the risk of recurrence and fully address the underlying fungal population.


Q: How quickly does Lamisil start killing the fungus?

The medicine is described as having a fungicidal action, meaning it actively kills the fungal cells. Topical forms begin working within one week, but the time for the full results of oral tablets to be seen in the nail is delayed due to the months required for healthy nail growth.

How should Lamisil be stored and disposed of?

Storage and Disposal of Lamisil (Terbinafine)

Storage Requirements

Lamisil, in both tablet and topical forms, must be stored at controlled room temperature, specifically between 20 to 25 C (68 to 77 F). The medication must be protected from light, excessive heat, and moisture, and it must not be frozen.

Keep the medicine in its original container with the lid tightly closed to maintain product integrity. The topical cream has a defined shelf-life of 28 days after first opening the tube. All forms must be kept out of the sight and reach of children.

Disposal Instructions

Expired or unused Lamisil should not be disposed of by flushing down a toilet or sink. The official regulatory guidance instructs patients to use a drug take-back program or consult with a pharmacist for proper local disposal procedures. If discarding in household trash is necessary, the medicine should be mixed with an undesirable substance, such as coffee grounds, before placing it in a sealed bag.

Attention! Always consult to a doctor or pharmacist before using pills or medicines.

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