Terbinafine: What it treats and how to use it safely

Terbinafine is an antifungal medicine you’ll see as a cream, spray, or a pill. People use it for skin infections like athlete’s foot, ringworm, and for stubborn nail fungus. Topical terbinafine treats many skin infections well and has few systemic side effects. Oral terbinafine works deeper—it's the go-to for fungal nails but needs more care because it affects the whole body.

How to use terbinafine

Topical: Apply the cream or solution to clean, dry skin once or twice daily as your prescriber or the label directs. Keep using it for the full course—stopping early lets the fungus return. For athlete’s foot and ringworm, a few weeks is typical; follow the instructions on the package or your doctor’s advice.

Oral: The most common dose for adults is 250 mg once daily for nail infections: roughly 6 weeks for fingernails and usually 12 weeks for toenails. Your provider might adjust the length based on how the nails respond. Don’t take oral terbinafine without a prescription and a quick health check—your liver should be in good shape first.

Side effects, warnings, and drug interactions

Common side effects are mild: stomach upset, headache, and taste changes. Taste loss (dysgeusia) can be distressing—mostly it’s temporary, but rare cases last longer. Watch for skin rash or itching; stop and call your doctor if you get hives or breathing trouble.

Serious but uncommon: liver injury. If you notice dark urine, yellowing of skin or eyes, persistent nausea, or severe tiredness, stop the medicine and seek care. Many doctors check liver tests before and during oral treatment if there are risk factors like heavy alcohol use or existing liver disease.

Terbinafine affects liver enzymes, especially CYP2D6. That can change levels of drugs like certain antidepressants, some beta-blockers, and tamoxifen. If you’re on other meds, tell your prescriber—drug interactions can matter. Also mention blood thinners and any history of liver problems.

Pregnancy and breastfeeding: Oral terbinafine is generally avoided in pregnancy unless a doctor decides benefits outweigh risks. If you’re pregnant, breastfeeding, or trying to conceive, discuss alternatives with your clinician. Topical terbinafine has much less systemic absorption and is often preferred in these situations.

Practical tips: Follow the full course even if symptoms improve. For nail fungus, expect slow progress—new healthy growth can take months to show. Keep feet dry, change socks regularly, and treat shoes with antifungal spray to lower the chance of reinfection.

Questions about dosing, interactions, or side effects? Talk to your doctor or pharmacist. They can check your meds and suggest the safest option for your situation.