TerbinafineTerbinafine Hydrochloride

About Terbinafine

Terbinafine is an allylamine antifungal: it blocks squalene epoxidase, an enzyme fungi need to make ergosterol for their cell membranes. The tablets are labeled for onychomycosis (nail infection) of the toenail or fingernail caused by dermatophytes, and the label asks for a nail sample (a KOH preparation, fungal culture or nail biopsy) to confirm the diagnosis first. The dose is one 250 mg tablet a day, for 6 weeks for fingernails or 12 weeks for toenails. Nails do not look better right away: the label says the full effect is seen some months after the fungus is cleared and treatment ends, as healthy nail grows out. Safety and effectiveness have not been established in children.

There is no boxed warning. Terbinafine must not be taken with chronic or active liver disease or after an allergic reaction to oral terbinafine. Liver failure, some cases leading to a transplant or death, has occurred in people with and without earlier liver disease, so liver function tests are done before it is prescribed and periodic monitoring is recommended; persistent nausea, loss of appetite, tiredness, vomiting, right upper abdominal pain, yellow skin or eyes, dark urine or pale stools mean stopping it and calling the prescriber. Taste or smell disturbance, including loss, can last more than a year or be permanent, and taste loss can lead to eating less, weight loss, anxiety and depressive symptoms; terbinafine is stopped if either occurs. Other warnings cover depressive symptoms, low white blood cell counts, serious skin reactions such as Stevens-Johnson syndrome and DRESS, new or worsening lupus, and thrombotic microangiopathy, some cases fatal. Headache, diarrhea, rash, indigestion, itching, taste disturbance and nausea are among the common side effects.

Terbinafine slows the breakdown of drugs cleared by the liver enzyme CYP2D6, so doses of some antidepressants, beta blockers and heart rhythm drugs may need lowering. In people with known or suspected immune deficiency, blood counts may be checked if treatment runs past 6 weeks. Pregnancy data are insufficient to judge the risk, the Medication Guide says to tell the doctor right away about a pregnancy during treatment, and terbinafine passes into breast milk. Lamisil tablets and Lamisil oral granules are discontinued. Over-the-counter terbinafine 1 percent cream (Lamisil AT and generic) is labeled to cure most athlete’s foot, jock itch and ringworm in adults and children 12 and older, and its label says not to use it on nails or the scalp; Lamisil AT spray is also sold over the counter.

Taking Terbinafine

How to take it

One tablet once a day, with or without food, for 6 weeks for fingernails or 12 weeks for toenails. Over-the-counter cream, for adults and children 12 and older: twice a day for 1 week between the toes or 2 weeks on the bottom or sides of the foot, and once a day for 1 week for jock itch or ringworm.

If you miss a dose

Take it as soon as you remember. If the next dose is due in less than 4 hours, skip the missed dose and take the next one at the usual time. Do not take a double dose.

Storage

Tablets and cream at room temperature (68 to 77 degrees F); keep tablets in a tightly closed container, away from light and out of reach of children.

Interactions to know about

It can raise levels of drugs broken down by CYP2D6, such as tricyclic antidepressants (desipramine), SSRIs, beta blockers, the antiarrhythmics flecainide and propafenone, and MAO-B inhibitors. Rifampin lowers terbinafine levels, while cimetidine and fluconazole raise them. It slows the clearance of caffeine and speeds that of cyclosporine.

This summarizes the official prescribing information. Your prescriber’s and pharmacist’s instructions, and the leaflet that comes with your medicine, take priority.

Why the cash price for Terbinafine differs from pharmacy to pharmacy

Generic terbinafine 250 mg tablets come from several makers, so quotes for the same course differ by each pharmacy’s fee and markup and by whether terbinafine is on its flat-price generic list. A fingernail course is 6 weeks and a toenail course 12 weeks, so the length written on the prescription sets the quantity, and a whole course on one prescription is quoted as one fill.

Liver tests are ordered by the prescriber and are not part of a pharmacy’s quote. The over-the-counter cream and spray are bought without a prescription and are not quoted with it.

Ways to pay less for Terbinafine without insurance

• Ask for the whole course (6 weeks for fingernails, 12 for toenails) on one prescription, so a quote covers the full treatment.
• Ask whether terbinafine is on the pharmacy’s flat-price generic list, and compare more than one pharmacy.
• For athlete’s foot, jock itch or ringworm on the skin, ask a pharmacist whether an over-the-counter terbinafine cream suits you, since the tablets are labeled only for nail infections.
• Upload the prescription to Script Unlock so licensed pharmacies can quote their cash price. You pay the pharmacy directly.

Questions to ask your pharmacist about Terbinafine

1. 1.When should my liver be tested, before and during treatment?
2. 2.Do my antidepressant, beta blocker or heart rhythm medicines interact with it?
3. 3.What should I do if my sense of taste or smell changes?
4. 4.How long will it take for my nail to look normal?

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