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Medical Disclaimer: This information is for educational purposes only and is not a substitute for professional medical advice.
Other
Terbinafine is a potent allylamine antifungal agent used primarily to treat fungal infections of the fingernails and toenails (onychomycosis) and various skin infections. It works by inhibiting the synthesis of ergosterol, a vital component of fungal cell membranes.
Name
Terbinafine
Raw Name
TERBINAFINE HYDROCHLORIDE
Category
Other
Salt Form
Hydrochloride
Drug Count
19
Variant Count
73
Last Verified
February 17, 2026
RxCUI
313222, 992528, 992530, 992535, 992536, 1739221
UNII
012C11ZU6G
About Terbinafine
Terbinafine is a potent allylamine antifungal agent used primarily to treat fungal infections of the fingernails and toenails (onychomycosis) and various skin infections. It works by inhibiting the synthesis of ergosterol, a vital component of fungal cell membranes.
Detailed information about Terbinafine
This page is for informational purposes only and does not replace medical advice. Consult a qualified healthcare professional before using any medication containing Terbinafine.
Terbinafine, commonly known in its salt form as Terbinafine Hydrochloride, is a highly effective antifungal medication belonging to the allylamine class. Since its initial FDA approval in the mid-1990s, it has become a cornerstone in the treatment of dermatophyte infections. Unlike many other antifungals that are fungistatic (meaning they only inhibit growth), terbinafine is primarily fungicidal against a wide range of dermatophytes, molds, and certain dimorphic fungi. It is most frequently prescribed for onychomycosis, a persistent fungal infection of the nail bed, but it is also utilized for tinea capitis (scalp ringworm), tinea corporis (body ringworm), and tinea pedis (athlete's foot).
According to the American Academy of Dermatology (2024), terbinafine remains a first-line systemic treatment for fungal nail infections due to its ability to penetrate the nail plate and remain active in the keratinized tissue for extended periods. It is classified pharmacologically as an allylamine derivative, distinguishing it from the azole class (such as fluconazole or itraconazole) by its unique point of intervention in the fungal biosynthetic pathway.
At the molecular level, terbinafine exerts its antifungal action by interfering with the early stages of fungal sterol biosynthesis. The primary target is the enzyme squalene epoxidase. This enzyme is responsible for converting squalene into lanosterol, which is a precursor to ergosterol. Ergosterol is a critical component of the fungal cell membrane, serving a similar role to cholesterol in human cells.
When terbinafine inhibits squalene epoxidase, two major events occur within the fungal cell. First, there is a significant deficiency in ergosterol, which weakens the cell membrane and increases its permeability, leading to cell lysis (breaking apart). Second, and perhaps more importantly, there is a rapid and toxic accumulation of squalene within the fungal cell. Squalene is a lipid that, in high concentrations, disrupts the intracellular lipid environment, leading to the death of the fungus. Because human squalene epoxidase is significantly less sensitive to terbinafine than the fungal version, the drug exhibits high selectivity for fungal cells over human cells.
Understanding how the body processes terbinafine is crucial for optimizing its efficacy and safety.
Terbinafine is FDA-approved for several specific indications, primarily focusing on infections caused by dermatophytes:
Terbinafine is available in several formulations to suit different patient needs:
> Important: Only your healthcare provider can determine if Terbinafine is right for your specific condition. A proper diagnosis, often involving a nail clipping or skin scraping for lab analysis, is essential before starting systemic antifungal therapy.
For adults, the standard dosage of terbinafine depends heavily on the location and severity of the fungal infection. According to standard clinical protocols (2024):
Terbinafine oral granules are FDA-approved for children 4 years of age and older for the treatment of tinea capitis. The dosage is typically based on the child's weight:
Healthcare providers generally do not recommend oral terbinafine for children under 4 years of age or for the treatment of onychomycosis in pediatric patients unless the benefits clearly outweigh the risks.
For patients with significant kidney dysfunction (creatinine clearance less than or equal to 50 mL/min), the use of oral terbinafine is generally not recommended. If it must be used, the dose may need to be reduced, and the patient must be monitored very closely for toxicity.
Terbinafine is strictly contraindicated (should not be used) in patients with chronic or active hepatic (liver) disease. Because the drug is extensively metabolized by the liver, impaired function can lead to dangerously high levels of the drug and further liver damage.
In geriatric populations, healthcare providers typically assess renal and hepatic function before prescribing. While age itself does not require a dose adjustment, the higher prevalence of decreased organ function in the elderly necessitates caution.
To ensure the best results and minimize side effects, follow these guidelines:
If you miss a dose, take it as soon as you remember. However, if it is almost time for your next scheduled dose (within 4 hours), skip the missed dose and resume your regular schedule. Never 'double up' on doses to make up for a missed one, as this increases the risk of side effects.
Symptoms of a terbinafine overdose may include severe nausea, vomiting, stomach pain, dizziness, or frequent urination. In the event of a suspected overdose, contact your local poison control center or seek emergency medical attention immediately. There is no specific antidote for terbinafine; treatment is generally supportive and focused on managing symptoms.
> Important: Follow your healthcare provider's dosing instructions exactly. Do not stop taking the medication early, even if the infection appears to be gone, as the fungus may still be present and could return if the full course is not completed.
Most patients tolerate terbinafine well, but some may experience mild to moderate side effects. These often resolve as the body adjusts to the medication:
> Warning: Stop taking Terbinafine and call your doctor immediately if you experience any of the following:
While terbinafine is typically taken for 6 to 12 weeks, its long-term presence in the body's tissues means side effects can occasionally emerge late in treatment or shortly after completion. The most notable long-term concern is the persistence of taste or smell disturbances, which in very rare instances can take months to fully resolve. There is no evidence that terbinafine causes permanent organ damage if used correctly and monitored by a physician, but the potential for delayed liver issues necessitates vigilance even after the final dose.
As of 2026, the FDA has not issued a formal 'Black Box Warning' for terbinafine tablets. However, the labeling contains prominent 'Warnings and Precautions' regarding hepatotoxicity. The FDA mandates that healthcare providers perform liver function tests (LFTs) before starting oral terbinafine and monitor patients for any clinical signs of liver injury throughout the treatment course. This warning is considered as serious as a black box warning by most clinical pharmacologists.
Report any unusual symptoms to your healthcare provider immediately. Early detection of side effects is key to preventing serious complications.
Terbinafine is a potent systemic medication that requires careful medical supervision. It is not suitable for everyone, particularly those with pre-existing liver conditions. Patients must be transparent with their healthcare providers regarding their full medical history, including any history of autoimmune diseases or kidney problems.
No FDA black box warnings for Terbinafine. However, the FDA-approved labeling includes significant warnings regarding the risk of liver failure, some cases of which have resulted in liver transplant or death. These events have occurred in patients both with and without pre-existing liver disease.
To ensure patient safety, the following monitoring is typically recommended:
Terbinafine generally does not affect the ability to drive or operate machinery. However, if you experience dizziness or visual disturbances as a side effect, you should avoid these activities until the symptoms resolve.
While there is no direct chemical interaction between alcohol and terbinafine, alcohol consumption can put additional stress on the liver. Since terbinafine carries a risk of hepatotoxicity, healthcare providers strongly advise limiting or avoiding alcohol during the course of treatment to minimize the risk of liver injury.
Terbinafine does not require a tapering period and does not carry a risk of withdrawal syndrome. However, it is vital to complete the full prescribed course. Stopping the medication early because the nail 'looks better' is a common mistake; the nail must grow out completely to ensure the fungus is eradicated, which can take several months after the drug is finished.
> Important: Discuss all your medical conditions with your healthcare provider before starting Terbinafine, especially if you have a history of liver disease, kidney disease, or a weakened immune system.
While few drugs are strictly contraindicated, the following should be avoided or managed with extreme caution due to the risk of severe adverse effects:
Because terbinafine is a potent inhibitor of the enzyme CYP2D6, it can increase the blood levels of many drugs metabolized by this pathway:
Terbinafine does not typically interfere with standard laboratory tests, but as mentioned, it will cause elevations in ALT and AST if liver injury occurs. It does not generally cause false positives on urine drug screens.
For each major interaction, the management strategy usually involves either selecting an alternative medication, adjusting the dose of the interacting drug, or increasing the frequency of clinical monitoring.
> Important: Tell your doctor about ALL medications, supplements, and herbal products you are taking, including over-the-counter pain relievers and vitamins.
There are specific scenarios where terbinafine must NEVER be used because the risks far outweigh any potential benefit:
These conditions require a careful risk-benefit analysis by a healthcare provider:
There is a potential for cross-sensitivity between terbinafine and other allylamine antifungals, such as naftifine. If a patient has reacted poorly to topical naftifine, they should be monitored closely if oral terbinafine is initiated, although the risk is considered low.
> Important: Your healthcare provider will evaluate your complete medical history, including baseline blood work, before prescribing Terbinafine to ensure it is safe for you.
Terbinafine was previously classified as FDA Pregnancy Category B. Animal studies have not shown evidence of fetal harm or impaired fertility. However, there are no adequate and well-controlled studies in pregnant women. Because the treatment of fungal nail infections is elective and not life-threatening, clinical guidelines generally recommend delaying oral terbinafine therapy until after pregnancy is complete. If a patient becomes pregnant while taking terbinafine, they should stop the medication and contact their obstetrician.
Terbinafine is excreted in human breast milk. Following oral administration, the ratio of terbinafine in milk to plasma is approximately 7:1. Because of the potential for adverse reactions in nursing infants, the use of oral terbinafine is generally not recommended for women who are breastfeeding. If treatment is essential, an alternative feeding method should be considered.
Terbinafine is approved for the treatment of tinea capitis in children aged 4 years and older. The safety and efficacy for onychomycosis in children have not been established in large-scale clinical trials. Pediatric patients require weight-based dosing and should be monitored for the same side effects as adults, particularly taste disturbances and skin rashes.
Clinical studies have not identified significant differences in responses between the elderly and younger patients. However, older adults are more likely to have decreased renal or hepatic function. A thorough review of the patient's medication list is essential for the elderly, as they are more likely to be taking drugs metabolized by CYP2D6 (such as certain heart medications or antidepressants).
In patients with moderate to severe renal impairment (CrCl ≤ 50 mL/min), the clearance of terbinafine is reduced by approximately 50%. There are no specific guidelines for dose reduction; instead, the current recommendation is to avoid use in this population entirely. Terbinafine is not significantly cleared by hemodialysis.
Terbinafine is contraindicated in patients with active or chronic liver disease. In patients with pre-existing stable hepatic impairment, the clearance of terbinafine can be reduced by 50%, leading to doubled blood concentrations. Due to the inherent risk of drug-induced liver injury, terbinafine should not be initiated in these patients.
> Important: Special populations require individualized medical assessment. Always inform your specialist if you are planning a pregnancy or have underlying organ dysfunction.
Terbinafine is an allylamine that inhibits the enzyme squalene epoxidase in the fungal sterol biosynthesis pathway. By blocking this enzyme, terbinafine prevents the conversion of squalene to lanosterol. This leads to a deficiency in ergosterol, which is essential for fungal cell membrane integrity. Simultaneously, the accumulation of intracellular squalene exerts a toxic effect, leading to rapid fungal cell death. This dual action makes terbinafine fungicidal against dermatophytes.
Terbinafine shows high specificity for fungal squalene epoxidase compared to the human version of the enzyme, which explains its relatively low toxicity in humans. The drug's effect is concentration-dependent. It is highly effective against Trichophyton species, Microsporum canis, and Epidermophyton floccosum. Its activity against yeasts (like Candida) varies and is often fungistatic rather than fungicidal.
| Parameter | Value |
|---|---|
| Bioavailability | ~40% (due to first-pass metabolism) |
| Protein Binding | >99% |
| Half-life | ~36 hours (steady state); ~200-400 hours (terminal) |
| Tmax | 2 hours |
| Metabolism | Hepatic (CYP2C9, 2C19, 3A4, 1A2) |
| Excretion | Renal 70%, Fecal 20% |
Terbinafine belongs to the Allylamine class of antifungals. It is distinct from the Azole class (e.g., ketoconazole) and the Polyene class (e.g., amphotericin B). Within the allylamine class, it is the most potent and widely used systemic agent.
Medications containing this ingredient
Common questions about Terbinafine
Terbinafine is primarily used to treat fungal infections of the fingernails and toenails, a condition known as onychomycosis. It is also effective for treating tinea capitis (scalp ringworm) in children and various skin infections like athlete's foot or jock itch when topical treatments fail. The medication works by killing the fungi that cause these infections by disrupting their cell membranes. It is considered a first-line treatment for nail fungus due to its ability to penetrate the nail tissue. Your doctor will confirm a fungal infection through testing before prescribing this systemic medication.
The most common side effects reported by patients taking terbinafine include headache, diarrhea, indigestion, and stomach pain. Many people also experience temporary changes in their sense of taste or smell, which can sometimes manifest as a metallic taste in the mouth. Skin rashes and itching are also relatively common. Most of these side effects are mild and go away on their own. However, if you notice persistent nausea or yellowing of the skin, you should contact your healthcare provider immediately as these could be signs of liver issues.
Healthcare providers generally recommend avoiding or strictly limiting alcohol consumption while taking oral terbinafine. Both terbinafine and alcohol are processed by the liver, and combining them can increase the workload and potential stress on this organ. Since terbinafine has a rare but serious risk of causing liver injury, it is safest to avoid alcohol to minimize any additional risk. If you have a history of heavy alcohol use, it is crucial to discuss this with your doctor before starting the medication. Always prioritize liver health during antifungal therapy.
Terbinafine is generally not recommended during pregnancy. While animal studies have not shown direct harm to the fetus, there is insufficient data from human clinical trials to guarantee its safety. Because fungal nail infections are not life-threatening, medical experts usually advise waiting until after delivery to begin treatment. If the infection is severe and treatment cannot wait, a doctor will perform a careful risk-benefit analysis. Always inform your healthcare provider if you are pregnant or planning to become pregnant before starting this drug.
While terbinafine begins killing the fungus shortly after you start taking it, you will not see a clear nail immediately. This is because the medication works by preventing new fungus from growing while the infected nail grows out. A fingernail may take 6 months to grow out fully, while a toenail can take 12 to 18 months. Therefore, the 'cure' is only visible long after the 6 or 12-week course of medication is finished. Patience is essential, and success is measured by the growth of a healthy, clear nail from the base.
Yes, you can stop taking terbinafine suddenly as it does not cause withdrawal symptoms or require a tapering schedule. However, you should only do so if directed by your doctor or if you experience a serious side effect like a severe rash or signs of liver trouble. Stopping the medication early simply because the symptoms seem to have improved can lead to a relapse of the infection. The fungus may not be entirely eradicated, allowing it to regrow. Always complete the full course of treatment as prescribed by your healthcare professional.
If you miss a dose of terbinafine, take it as soon as you remember. If it is within 4 hours of your next scheduled dose, skip the missed dose and continue with your regular timing. Do not take two doses at once to make up for the one you missed, as this can increase the likelihood of experiencing side effects like stomach upset or headache. Consistency is key for antifungal medications to work effectively. Setting a daily alarm can help you remember to take the medication at the same time each day.
Weight gain is not a recognized or common side effect of terbinafine. Clinical trials and post-marketing surveillance have not shown a significant link between this medication and changes in body weight. If you experience rapid or unexplained weight gain while taking terbinafine, it is likely due to another factor or an underlying medical condition. Some patients might experience a loss of appetite if they develop taste disturbances, which could theoretically lead to slight weight loss. Always discuss significant changes in weight with your healthcare provider.
Terbinafine can interact with several other medications, particularly those processed by the liver enzyme CYP2D6. This includes certain antidepressants, beta-blockers, and heart rhythm medications. It can also interact with the antibiotic rifampin and the stomach acid medicine cimetidine. Because of these potential interactions, it is vital to provide your doctor with a complete list of all prescription drugs, over-the-counter medicines, and herbal supplements you are taking. Your doctor may need to adjust your dosages or monitor you more closely while you are on terbinafine.
Yes, terbinafine is widely available as a generic medication in tablet form, which is typically much more affordable than the brand-name version, Lamisil. Generic terbinafine is required by the FDA to have the same active ingredient, strength, dosage form, and route of administration as the brand-name drug. It must also prove bioequivalence, meaning it works in the body the same way. Most insurance plans cover the generic version of terbinafine. You can consult your pharmacist to ensure you are receiving the most cost-effective version of your prescription.