Terbinafine

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Benjamin Clanner-Engelshofen is a freelance writer in the medical department. He studied biochemistry and pharmacy in Munich and Cambridge / Boston (USA) and noticed early on that he particularly enjoyed the interface between medicine and science. That is why he went on to study human medicine.

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The active ingredient terbinafine is used as an antifungal agent to treat skin, foot or nail fungus. Due to its chemical structure, it belongs to the group of allylamines. The treatment can be applied externally (as a cream, nail polish, etc.) or internally (in the form of tablets). Here you can read everything interesting about the effects and use of terbinafine, side effects and interactions.

This is how terbinafine works

Like animals and humans, fungi also consist of individual cells that can, under certain conditions, be individually viable. The cell is thus the smallest, independent structural unit of all forms of life. In order to purposefully and selectively only damage the fungal cells in the event of an infection with a fungus, one makes use of the differences in life forms. These differences are not very large at the cellular level (for example, humans and mold are more closely related to one another than some types of bacteria are to one another). Therefore, many antimycotics target the cell membrane, which is structured differently in fungi and humans.

In humans and in many animals, the membrane that separates the cell from the outside and makes many metabolic pathways possible in the first place consists mainly of special lipids such as cholesterol. Cholesterol gives the cell membrane the flexibility it needs to cope with environmental influences. In mushrooms, this task is performed by the substance ergosterol, which is chemically similar to cholesterol, but has a different structure in some points.

The active ingredient terbinafine inhibits the production of ergosterol in the fungal cells. The resulting lack of ergosterol in the membrane inhibits the growth of the fungal cells or even causes them to die.

Uptake, degradation and excretion of terbinafine

After ingestion, the active ingredient terbinafine is well absorbed in the intestines.However, some of it is quickly broken down in the liver, so that only about half of the administered dose reaches the large bloodstream, where the highest levels can be measured after one and a half hours. Since the active ingredient is very soluble in fat, it gets into the skin and nails easily. Half of the active ingredient is excreted after about 30 hours.

Terbinafine can be broken down by many different subforms of the cytochrome P450 enzyme, which is necessary to make it more water-soluble. The breakdown products are excreted via the kidneys with the urine or via the intestines with the stool.

When is terbinafine used?

The antifungal drug terbinafine is used to treat skin and nail fungal diseases. In the case of fungal skin disease, it is usually used locally (e.g. as a terbinafine cream). There is also water-soluble nail polish with terbinafine for the treatment of mild to moderate nail fungus. In the case of a severe fungal skin or nail infection, the therapy is systemic (in the form of terbinafine tablets).

The application is usually only a few weeks for skin fungus, but sometimes for several months for nail fungus.

This is how terbinafine is used

In the treatment of skin fungal diseases, terbinafine is used as a one percent cream, gel or spray. It should be applied to the affected and adjacent areas once or twice a day. The application takes one to two weeks, depending on the type of infection.

A water-soluble nail polish is available against light to moderate nail fungus infestation. It is applied to the entire affected nail plate, the surrounding skin and below the front edge of the nail. After six hours, the paint residue can be removed with water.

In the case of severe skin fungal infections or nail fungus diseases, the therapy takes the form of terbinafine tablets, each with 250 milligrams of active ingredient. The tablets are taken once a day with a glass of water with or without food. Terbinafine should always be taken at the same time of day. Depending on the severity of the disease, terbinafine is usually taken for four to six weeks (in the case of skin fungal infections) or for a period of up to three months (in the case of nail fungal infections).

What side effects does terbinafine have?

While taking terbinafine, more than ten percent of those treated experience headache, decreased appetite, gastrointestinal complaints (such as nausea, abdominal pain, diarrhea), skin reactions (such as rash and itching), muscle and joint pain.

One in ten to one hundred patients reports terbinafine side effects such as depression, taste disorders, loss of taste and fatigue.

The side effects presented here mainly occur when taking terbinafine. When applied to the skin, the side effects are at most very mild. Terbinafine nail polish occasionally causes redness and skin irritation.

What should be considered when using terbinafine?

Since terbinafine is broken down by enzymes in the liver, which also break down many other drugs and substances foreign to the body, taking it at the same time can influence the active ingredient levels of each individual substance - i.e. both increase and decrease:

In particular, active ingredients metabolized via the enzyme cytochrome P450 2D6 are broken down more slowly in combination with terbinafine and can thus accumulate in the body. These include, for example, agents against depression (tricyclic antidepressants, selective serotonin reuptake inhibitors, MAO inhibitors), agents that stabilize the heart rhythm (antiarrhythmics of classes 1A, 1B and 1C) and beta blockers (cardiovascular agents).

Since only very limited data are available on the use of terbinafine in pregnant women, the active ingredient should not be used during pregnancy as a precaution. The same applies to breastfeeding. The use of terbinafine is also not recommended in children.

Elderly patients (over 65 years of age) can take terbinafine, but liver and kidney function should be checked beforehand. Patients with liver or kidney problems should not take terbinafine.

How to get medicines with terbinafine

Preparations for use on the skin with a maximum of one percent active ingredient content are available in pharmacies without a prescription. The same applies to terbinafine nail polish. Terbinafine tablets for ingestion require a prescription.

How long has terbinafine been known?

Terbinafine was marketed by the pharmaceutical company Novartis in Europe in 1991 and in the USA in 1996. The patent expired in 2007, after which an extension patent for treating children in the United States was filed. In Germany, however, numerous generics with the active ingredient terbinafine are already available.

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