How Exactly Does Terbinafine Work to Treat Jock Itch?

What is terbinafine?

Terbinafine is an antifungal that works by stopping fungi from growing. Topical terbinafine is used for the treatment of fungal skin infections, such as ringworm, jock itch, and athlete's foot. Oral terbinafine tablets are often prescribed when it comes to treating fungal infections of the fingernails and toenails. For the treatment of scalp fungus, terbinafine granules are used. 

Only fungal infections are treated by this drug. It does not treat viral or bacterial infections. On an average, the effect of this medication lasts for 24-30 hours. The effects of the medicine can be observed 1-2 hours after its application.

How does it work?

Terbinafine is an antifungal medicine that treats fungal infections. The cell membrane of fungus is essential for its survival. Terbinafine works by causing holes in the fungal cell membrane. 

Fungal cell membranes keep unwanted elements from entering the cells. They also prevent cell contents from leaking out. What terbinafine does is that it causes holes in the fungal cell membranes to kill the fungus and clear up the infection. 

How to Use Terbinafine for Jock Itch

Topical terbinafine should only be used on the skin. Before application, the affected area should be clean and dry. Make sure to only apply a thin layer of the medication to the affected area. Usually, this medication is applied once or twice a day. You can also read and follow the instructions on the medicine label. Consult your doctor or pharmacist if you are unsure of the information provided on the product package. 

It is also important to wash your hands before and after application unless the treated area includes your hands. Avoid covering, wrapping, or putting a bandage on the affected area unless otherwise instructed by your doctor. Be careful not to apply this medication in your mouth, eyes, or vagina. If the medication gets into these areas, make sure to wash off using plenty of water. This medication should not also be applied on the nails or scalp unless otherwise instructed by your doctor. 

The length of treatment and corresponding dosage usually depend on the type and severity of the fungal infection. Apply this medication at the same time every day. Do not use this medication for a longer period than prescribed to avoid developing unwanted side effects. 

A full course of treatment using this medication should be followed even if you already feel better and the symptoms start to fade away. Infections tend to recur if the medication is early stopped. Complete healing from the infection may take several weeks after a full treatment. 

In cases wherein you miss a dose, use the medication as soon as you remember. However, if it is already time for the next dose, skip the missed dose and continue with your usual dosing schedule. Avoid taking double doses to catch up for the missed ones. 

Seek immediate medical help if your symptoms for ringworm, athlete's foot, and jock itch do not improve within 14 days or if the infection seems to get worse.  

Precautions

Do not use terbinafine and other allylamine antifungals, such as naftifine if you are allergic to them or have other types of allergies. The inactive ingredients of this product may trigger an allergic reaction or other health issues. If you have allergies or other health conditions, consult your doctor or pharmacist before using this product. 

This medication should only be used when clearly needed during pregnancy. Pregnant women can discuss the benefits and risks of using this medication with their doctor. When other forms of terbinafine are orally taken, some of the medication may pass into breast milk. It is unknown whether terbinafine passes into breast milk when it is applied to the skin. Consult your doctor and discuss the pros and cons of using this medication while breastfeeding. 

Side Effects

There are also unwanted side effects that are associated with terbinafine. They may include:

• Fever
• Chills
• Headache
• Body aches or joint pain
• Diarrhea
• Indigestion
• Itching
• Mood changes
• Feeling weak or tired
• Trouble sleeping

Although terbinafine rarely causes serious side effects, seek immediate medical help if you experience any of the following:

• Nausea and vomiting
• Loss of appetite
• Passing dark-colored urine or pale stool
• Presence of blood in urine
• Extreme tiredness
• Jaundice (yellowing of the eyes and skin)
• Fever
• Sore throat
• Difficulty swallowing
• Upper right side abdominal pain 
• Itching or hives
• A worsening skin rash
• Swelling of the face, eyes, throat, lips, or tongue
• Swollen lymph nodes
• Difficulty breathing
• Chest pain
• Irregular or fast heartbeat
• Unexplained bruising or bleeding 

Terbinafine may also cause other side effects that are not mentioned in this article. Consult your doctor if you develop unusual symptoms while taking terbinafine. 

Contraindications

People who have the following medical conditions should consult their doctor before using oral terbinafine:

• Liver disease and other liver problems
• Systemic lupus erythematosus (SLE)
• Depression
• Lactating and breastfeeding mothers
• Severe neutropenia (abnormally low neutrophil count in the blood)
• Terbinafine or butenafine allergy

What should I know before taking terbinafine?

The use of terbinafine may occasionally cause liver problems. In some cases, doctors recommend liver function tests to patients before starting treatment. After using this medication for 4-6 weeks, a liver function test may be repeated to check for any signs of liver problems. Seek immediate medical help if you develop any of the following symptoms during treatment:

• Fatigue
• Skin itching
• Jaundice (yellowing of the eyes and skin)
• Dark-colored urine
• Pale stool
• Upper right abdominal pain or discomfort
• Nausea
• Vomiting
• Loss of appetite

People with liver disease and women who are breastfeeding should not take terbinafine. The use of this medication for children is also not approved. In some cases, this medication can make psoriasis worse. People with SLE should also take this medication with caution.  

Interactions

The following products may cause interactions with terbinafine:

• Warfarin
• Rifampin
• Cimetidine
• Amiodarone
• Fluconazole
• Ketoconazole
• Beta-blockers (timolol, propranolol, metoprolol)
• Tricyclic antidepressants (nortriptyline, amitriptyline, imipramine)
• Selective serotonin reuptake inhibitors (SSRIs)
• Dextromethorphan
• Thioridazine
• Rasagiline (monoamine oxidase inhibitor type B)

Medications that Contain Terbinafine

Terbinafine is a generic medicine. The following medications are brand names of terbinafine:

• Lamisil Tablets
• Lamisil Cream
• Lamisil Once 1%
• Lamisil AT Cream
• Lamisil AT Spray
• Lamisil AT Gel