Terbinafine: tablets or cream, liver values and the real treatment duration

Terbinafine is one of the most important agents against foot and nail fungus. The active ingredient exists in two very different forms: as a cream, gel or spray for application and as a tablet for intake. Exactly here lies the decisive question that this guide answers: when is the external treatment enough and when are tablets needed? Besides this, it is about two points that often come up short: why the liver values are checked with the tablets and how long a nail fungus treatment really takes. The text explains this factually and realistically, without false promises and without unnecessary panic. It does not replace medical advice but helps you discuss the right treatment with your practice.

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At a glance

  • Terbinafine is an antifungal against fungi, especially against the thread fungi of foot and nail fungus.
  • With mild foot fungus the cream is often enough; with nail fungus tablets are frequently needed.
  • Before the tablet therapy and sometimes during it, the liver values are checked.
  • Nail fungus needs patience: the tablets work for weeks to months, the nail grows out for a long time afterwards.
  • The cream is partly over the counter; the tablets are always prescription only.

What is terbinafine and how does it work?

Terbinafine belongs to the group of antifungals, that is the agents against fungi, and more precisely to the subgroup of allylamines. To understand how it works, a look at the fungal cell helps. Fungi need for their cell shell a special building block called ergosterol, comparable to the cholesterol in human cells. Without ergosterol the shell of the fungus becomes unstable and leaky. Exactly here is where terbinafine intervenes.

The active ingredient inhibits an enzyme with the name squalene epoxidase that the fungus needs to produce ergosterol. If this enzyme is blocked, the fungus can no longer form ergosterol, its cell shell is damaged and the fungus dies off. Against the thread fungi that cause foot and nail fungus, terbinafine works not only inhibiting but directly killing. This makes it a very effective agent precisely with these common infections. Terbinafine exists in two basic forms of application: for application on skin and nail as a cream, gel, spray or solution, and for intake as a tablet that works in the whole body. If the external treatment alone is not enough, with itraconazole and fluconazole further active ingredients are available as alternatives for the internal therapy, about which it is decided medically in the individual case.

Two routes, one active ingredient

The most important difference with terbinafine is not the active ingredient itself but how it is applied. The external application as a cream or spray works only where it is applied and hardly reaches the body. The tablet, on the other hand, distributes via the blood in the whole body and thereby also reaches deep-seated infections, for example in the nail root. This stronger effect has, however, also its price in the form of possible side effects and the need for medical accompaniment.

Tablets or cream? The decisive question

The most important decision with terbinafine is whether the external treatment is enough or whether tablets are needed. This question cannot be answered in a blanket way, but there are clear pointers. With superficial foot fungus, that is redness, itching and scaling between the toes or on the sole of the foot, the external treatment with cream, gel or spray is enough in most cases. It is applied consistently over a few weeks, also for a while after the symptoms subside, so that no fungal spores remain. Exactly this stopping too early is, with foot fungus, the most common reason why the infection returns after a short time.

With nail fungus the matter looks different. The nail is a hard, dense structure into which active ingredients from outside penetrate only with difficulty. A cream or a nail lacquer can be tried with very mild, superficial infestation of a single nail but often reaches its limits. If several nails are affected, the infestation reaches the nail root or a large part of the nail is diseased, tablets are as a rule needed, because only they reach the fungus via the blood from the inside too. With people with diabetes, circulation disorders or a weakened immune system, the tablet is rather advised too, to prevent a spread. Frequently tablets and external treatment are combined because this has proven particularly effective. Which route is right in the individual case is decided by the medical practice after examination. Helpful is also a fungus detection from a sample, because not every discolouration or thickening of a nail is actually a fungus. Sometimes psoriasis, an injury or other causes are behind it that must be treated differently, which is why a reliable diagnosis before a months-long therapy is sensible.

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Liver values: why the check is important

When terbinafine is taken as a tablet, the active ingredient works in the whole body and is broken down above all via the liver. In the vast majority of cases the liver tolerates this well; in rare cases terbinafine can, however, strain or damage it. Therefore a check of the liver values belongs to a responsible tablet therapy. Before the start, blood is as a rule taken to check whether the liver is healthy, and with a longer intake this check can be repeated. This way changes can be recognised early, long before they cause complaints, and the therapy can if needed be adjusted or ended in time. This check is no reason for worry but a deliberate safety step that makes the tablet therapy reliable.

With an existing liver disease, the tablet therapy is mostly not suitable; here alternatives are sought, for example an external treatment or another active ingredient. During the intake you should watch out for certain warning signs that can point to a liver problem: a yellowing of skin or eyes, unusually dark urine, light stool, persistent nausea, loss of appetite or unusual fatigue. If such signs occur, you should stop the agent and seek medical advice immediately. These precautions sound serious but are exactly the reason why the tablets are prescription only and are medically accompanied, so that the therapy stays safe.

Watch out for liver signs

During a tablet therapy with terbinafine, watch out for warning signs of the liver: yellow skin or eyes, dark urine, light stool, persistent nausea or unusual fatigue. Stop the agent with such signs and seek medical help. During the therapy, drink as little alcohol as possible or none, because it too strains the liver. Name to your medical practice beforehand all previous liver diseases and all further medicines you take.

The real treatment duration with nail fungus

A point at which many treatments fail is patience. Nail fungus is stubborn, and the therapy lasts clearly longer than many expect. With a tablet therapy the tablets are mostly taken over several weeks to months, with fingernails often about six weeks, with toenails often about three months. But here lies the decisive and often misunderstood point: even when the tablets are stopped, the nail still looks ill for a long time.

The reason is simple. Terbinafine kills the fungus off but cannot repair the already damaged part of the nail. The ill nail must first grow out and be replaced by a healthy, new nail. With fingernails this takes a few months; with the slowly growing toenails it can take up to a year until the nail looks completely healthy again. This means: the actual treatment success only shows months after the end of the intake. Anyone who does not know this perhaps considers the treatment failed or breaks it off too early. Important is therefore to consistently keep to the prescribed intake duration, even if nothing visible happens for a long time, and to give the nail time to grow out afterwards. Many people break off exactly here because they see no improvement after a few weeks and consider the agent ineffective. This fallacy is one of the most common reasons for an apparent failure and a later relapse. Anyone who knows from the start that the visible success only comes late stays rather consistently on it.

Situation Mostly external treatment Mostly tablets
Foot fungus, superficial yes, cream or spray only with failure
Single nail, mild attempt with lacquer possible often needed
Several nails or nail root mostly not sufficient yes
Diabetes or immune weakness only supplementary rather yes

Side effects and the look at the skin

With the external application as a cream or spray, side effects are rare and mostly limited to mild skin irritations, redness or itching at the treated place. This is because hardly any active ingredient reaches the body. With the tablets it is different. The most common are gastrointestinal complaints such as loss of appetite, nausea and a feeling of fullness. Characteristic for terbinafine is also a temporary taste disorder: some users perceive food as bland or changed. This is unpleasant but as a rule recedes after stopping. In rare cases the taste disorder can last several weeks and temporarily reduce the appetite, which is why precisely with a longer intake attention should be paid to a sufficient nutrition.

Rarer but important to know are more serious reactions. These include strains of the liver, at which the liver value check is aimed, as well as severe skin reactions. Exactly for this reason the skin deserves special attention. A mild, local itch is harmless. If a skin rash, however, spreads quickly or goes along with blisters, peeling of the skin, fever or an involvement of the mucous membranes, this can be a sign of a rare but serious skin reaction. In this case you should stop the tablets immediately and seek medical help without delay. Such severe reactions are rare, but they show why a medical accompaniment of the tablet therapy is important.

Act immediately with a spreading skin rash

Stop terbinafine tablets immediately and seek medical help without delay if a skin rash spreads quickly or goes along with blisters, peeling of the skin, fever or involvement of the mucous membranes, for example in the mouth. These can be signs of a rare but severe skin reaction that must be treated quickly. In such a case, do not wait and do not take the tablet further but have the reaction assessed medically. With a mild, local itch, on the other hand, this is not necessary.

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In sum, terbinafine is a very effective agent against foot and nail fungus if it is used correctly. The most important setting of the course is the choice between external treatment and tablets: with mild foot fungus the cream is often enough, with nail fungus tablets are frequently needed. Anyone who takes tablets should have the liver values checked, watch out for warning signs and above all bring patience, because the nail needs months to grow out. With nail fungus, terbinafine is often the agent of choice; with foot fungus the external application is mostly enough. If a skin rash occurs that spreads, medical advice is needed.

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Frequently asked questions about terbinafine

Terbinafine is an antifungal from the group of allylamines. It inhibits an enzyme that the fungus needs to produce ergosterol, a building block of its cell shell. Without ergosterol the shell is damaged and the fungus dies off. Terbinafine works particularly well against the thread fungi of foot and nail fungus. The active ingredient exists as a cream, gel, spray and as a tablet.
With superficial foot fungus the cream is mostly enough. With nail fungus a cream or lacquer often reaches its limits because the active ingredient penetrates the nail poorly. If several nails, the nail root or a large part are affected or the external treatment has failed, tablets are mostly needed. With diabetes or immune weakness the tablet is rather advised. The decision is made by the medical practice.
Terbinafine tablets are broken down via the liver and can in rare cases strain it. Therefore the liver values are checked before the start and sometimes during the therapy. With a liver disease the tablet is mostly not suitable. With yellowing of skin or eyes, dark urine, persistent nausea or fatigue, stop the agent and seek medical advice immediately.
The tablets are mostly taken for weeks to months, with fingernails often about six weeks, with toenails often about three months. Important: the nail still looks ill for a long time after stopping, because the healthy nail must first grow out, with toenails up to a year. The success only shows months later. Do not break off the therapy too early.
With the cream, side effects are rare and mostly limited to mild skin irritations. With the tablets, gastrointestinal complaints are most common, plus a temporary taste disorder, headaches and skin rashes. Rare are serious liver or skin reactions. With a spreading rash or blistering, stop the agent immediately and seek medical help.
A mild, local itch is mostly harmless. You should become alert if a rash spreads quickly or goes along with blisters, peeling of the skin, fever or involvement of the mucous membranes. These can be signs of a rare but serious skin reaction. Then stop the tablets immediately and seek medical help without delay.
Yes, a relapse is not rare because fungal spores can survive in shoes, stockings or in the bathroom. Important is to carry the therapy through consistently and to observe accompanying measures: keep feet dry, treat or change shoes and stockings, avoid walking barefoot in public baths. With a renewed infestation, have the cause clarified medically.
Yes, terbinafine tablets can interact with other medicines, for example with some antidepressants and beta blockers whose effect can be strengthened. Therefore name to your medical practice and pharmacy all the agents you take, also over-the-counter ones. The cream, on the other hand, has hardly any relevant interactions because only little active ingredient reaches the body.
Terbinafine for application, as a cream, gel or spray, is partly available over the counter and can with mild foot fungus often be used yourself, best after advice in the pharmacy. The tablets are always prescription only. With nail fungus or stubborn infestation, a medical clarification should take place, because not every nail discolouration is caused by fungi.

Related topics

Sources

  • Gelbe Liste: terbinafine, use, effect, side effects
  • Deutsche Apotheker Zeitung: terbinafine, topical and systemic application
  • PTAheute: nail fungus, systemic therapy and S1 guideline onychomycosis
  • Drug commission of the German medical profession / Deutsches Ärzteblatt: terbinafine and severe skin reactions
  • gesundheit.de: terbinafine, effect and side effects
  • dermanostic / docmorris: terbinafine, dosage forms and treatment duration

This guide serves general information and does not replace medical advice, diagnosis or treatment. It contains no dosage recommendation. Terbinafine tablets are prescription only. Take them only on medical prescription, have the liver values checked and seek medical help immediately with warning signs of the liver or a spreading skin rash. With questions, turn to your medical practice or pharmacy.