terbinafine
Brand names: Lamisil
Terbinafine is an antifungal medicine. It is used to treat fungal infections of the fingernails and toenails.
Drug Pricing (NADAC)
Generic Price
$0.28/unit
Generic Available
Yes (8 manufacturers)
Pricing data from NADAC (CMS), effective December 18, 2024. Compare all drug costs →
What it does
Terbinafine treats onychomycosis, a fungal infection of the toenails or fingernails.
Common side effects
Headache, Diarrhea, Rash
Key warnings
Terbinafine can cause liver problems, including liver failure.
How It Works
Terbinafine belongs to a class of medicines called allylamine antifungals. It works by stopping the growth of fungi. This eventually kills the fungus causing the infection.
How to Take It
Take one 250 mg tablet once a day. For fingernail infections, you will take it for 6 weeks. For toenail infections, you will take it for 12 weeks. It may take several months after you stop taking the medicine to see the full effect.
Pregnancy & Breastfeeding
Talk to your doctor if you are pregnant or plan to become pregnant. It is not known if terbinafine will harm your unborn baby. Terbinafine passes into breast milk. Talk to your doctor about the risks and benefits of breastfeeding while taking this medicine.
Missed Dose
If you miss a dose, take it as soon as you remember. If it is close to your next dose, skip the missed dose and continue with your regular schedule.
Storage
Store terbinafine tablets at room temperature, away from light.
Side Effects (from patient reports)
Based on 3,216 FDA adverse event reports.
FDA Adverse Event Report Analysis
Detailed analysis of 6,848 reports from the FDA Adverse Event Reporting System (FAERS). Reports span 2003–2025.
Total Reports
6,848
Death-Related Reports
428
Hospitalization Reports
1,849
Top Indication
Product Used For Unknown Indication
Gender Distribution
Age Distribution
Most Reported Adverse Reactions (FAERS)
| # | Reaction | Reports |
|---|---|---|
| 1 | DRUG INEFFECTIVE | 685 |
| 2 | RASH | 391 |
| 3 | PRURITUS | 316 |
| 4 | FATIGUE | 300 |
| 5 | NAUSEA | 280 |
| 6 | AGEUSIA | 270 |
| 7 | PAIN | 267 |
| 8 | OFF LABEL USE | 254 |
| 9 | HEADACHE | 229 |
| 10 | DRUG INTERACTION | 224 |
| 11 | DIARRHOEA | 217 |
| 12 | MALAISE | 217 |
| 13 | DRUG RESISTANCE | 196 |
| 14 | ANXIETY | 194 |
| 15 | CHRONIC KIDNEY DISEASE | 194 |
Reactions in Death Reports
Reactions in Hospitalization Reports
Source: FDA FAERS (Adverse Event Reporting System) FDA FAERS (Adverse Event Reporting System) Reports are voluntary and do not establish causation
Serious Warnings
Terbinafine can cause liver problems, including liver failure. Your doctor should check your liver before you start taking it and regularly while you are taking it. Tell your doctor right away if you have nausea, loss of appetite, tiredness, vomiting, pain in your upper right belly area, yellowing of the skin or eyes, dark urine, or pale stools. If you have taste changes, stop taking terbinafine. These changes can be severe, long-lasting, or even permanent. Tell your doctor if you feel depressed or have other mood changes.
Known Drug Interactions
Tamsulosin hydrochloride capsules should be used with caution in combination with moderate inhibitors of CYP3A4 (e.g., erythromycin), in combination with strong (e.g., paroxetine) or moderate (e.g., terbinafine) inhibitors of CYP2D6, or in patients known to be CYP2D6 poor metabolizers, particularly at a dose higher than 0.4 mg (e.g., 0.8 mg). The effects of concomitant administration of a moderate CYP2D6 inhibitor (e.g., terbinafine) on the pharmacokinetics of tamsulosin hydrochloride have not been evaluated [see Warnings and Precautions (5.2) and Clinical Pharmacology (12.3)].
Mechanism: Terbinafine slows down the body's ability to break down tamsulosin by blocking a specific liver enzyme. This can lead to higher levels of tamsulosin in your blood.
What to do: Use this combination with caution. Your doctor may need to adjust your dose, especially if you are taking more than 0.4 mg of tamsulosin.
Based on this finding, it is likely that other inhibitors of both CYP2C9 and CYP3A4 (e.g., ketoconazole, amiodarone) may also lead to a substantial increase in the systemic exposure (C max and AUC) of terbinafine when concomitantly administered.
Mechanism: Ketoconazole stops the body from breaking down terbinafine, which can lead to much higher levels of terbinafine in your blood.
What to do: Your doctor may need to adjust your terbinafine dose or monitor you more closely for side effects.
Drug interactions have also been noted with cimetidine, fluconazole, cyclosporine, rifampin, and caffeine. The influence of terbinafine on the pharmacokinetics of fluconazole, cotrimoxazole (trimethoprim and sulfamethoxazole), zidovudine or theophylline was not considered to be clinically significant. Coadministration of a single dose of fluconazole (100 mg) with a single dose of terbinafine resulted in a 52% and 69% increase in terbinafine C max and AUC, respectively.
Mechanism: Fluconazole interferes with the way the body processes terbinafine, leading to higher amounts of terbinafine in the bloodstream.
What to do: Your doctor may need to watch for increased side effects or adjust your terbinafine dose.
Drug interactions have also been noted with cimetidine, fluconazole, cyclosporine, rifampin, and caffeine. In vitro studies with human liver microsomes showed that terbinafine does not inhibit the metabolism of tolbutamide, ethinylestradiol, ethoxycoumarin, cyclosporine, cisapride and fluvastatin. Terbinafine increases the clearance of cyclosporine by 15%.
Mechanism: Terbinafine makes the body get rid of cyclosporine more quickly than normal.
What to do: Your doctor may need to check your blood levels and adjust your cyclosporine dose to make sure it still works.
The influence of terbinafine on the pharmacokinetics of fluconazole, cotrimoxazole (trimethoprim and sulfamethoxazole), zidovudine or theophylline was not considered to be clinically significant.
Mechanism: Terbinafine does not significantly change how the body handles trimethoprim.
What to do: You can typically take these medications together without needing any dose changes.
Common Questions
Can I drink alcohol while taking terbinafine?
How long does it take for terbinafine to work?
What should I do if I get a rash while taking terbinafine?
Can terbinafine interact with other medicines I am taking?
What if I have kidney problems?
Will terbinafine cause my hair to fall out?
Can terbinafine cause depression?
Is there a generic version of terbinafine?
What do the tablets look like?
What if I have an allergic reaction?
What are the common side effects of terbinafine?
Does terbinafine interact with other medications?
What drug class is terbinafine?
Is terbinafine safe during pregnancy?
Related Medications in Allylamine Antifungal
Other drugs grouped near terbinafine — same-class peers and common alternatives.
acyclovir
Zovirax
Acyclovir is an antiviral medicine.
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albendazole
Albenza
Albendazole is a medicine that fights parasites.
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amphotericin B
Ambisome, Fungizone
Amphotericin B liposome is an antifungal medicine.
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anidulafungin
Eraxis
Eraxis is an antifungal medicine.
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atovaquone/proguanil
Malarone
Malarone is a drug used to prevent and treat malaria.
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Medication Guides
Understanding Drug Interactions
How CYP450 enzymes, inhibitors, and inducers affect your medications
Generic vs Brand Name Drugs
FDA requirements, cost savings, and when the difference matters
Narrow Therapeutic Index Drugs
Why some drugs demand precise dosing and monitoring
Common Drug Interactions
Dangerous medication combinations and how to protect yourself
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What the FDA Data Shows for terbinafine
The FDA label for terbinafine (sold under brand names such as Lamisil) classifies it as a prescription-only medication in the Allylamine Antifungal class. Terbinafine treats onychomycosis, a fungal infection of the toenails or fingernails. Official labeling lists 10 commonly reported side effects, including Headache, Diarrhea, Rash.
Post-market surveillance from the FDA Adverse Event Reporting System (FAERS) captures real-world experience. For this drug, FAERS contains 3,216 voluntary reports. The database also lists 17 documented drug interactions derived from FDA labeling, with the top-flagged interaction rated moderate severity. NADAC pricing from CMS shows a generic unit cost of $0.28.
Report counts do not establish causation — a FAERS entry documents a temporal association, not proof that the drug produced the outcome. Widely prescribed medications naturally accumulate more reports than niche therapies, so raw totals must be interpreted alongside total exposure. Shortage status, recall history, and patent information further shape supply and switching decisions. This page summarizes public FDA data for educational purposes only and is not a substitute for professional medical advice — always consult a licensed healthcare provider before starting, stopping, or changing any medication.
Data Sources
Drug labeling: FDA Drug Labels (SPL/DailyMed). Adverse events: FDA Adverse Event Reporting System (FAERS). Pricing: CMS National Average Drug Acquisition Cost (NADAC).
FAERS reports are voluntary and do not establish causation. Drug interactions are derived from FDA labeling and clinical references. Always consult a healthcare professional before making medication decisions.
Last updated: September 30, 2025
Read our methodology — how this data is sourced, computed, and verified.
All federal data sources used on this page
- FDA Orange Book — approved drug products with therapeutic equivalence. accessdata.fda.gov/cder/ob
- FDA DailyMed — NIH-hosted drug labeling for FDA-approved meds. dailymed.nlm.nih.gov
- FDA Adverse Event Reporting System (FAERS) — post-marketing safety surveillance. fda.gov/drugs/faers
- NLM RxNorm — standardized clinical drug nomenclature. nlm.nih.gov/research/umls/rxnorm
- CMS Medicare Part B Drug Average Sales Price Files — federal drug pricing data. cms.gov/medicare/part-b-drugs/asp
- FDA Drug Shortages Database — current and resolved drug shortage tracking. accessdata.fda.gov/drugshortages