What are the side effects of Terbinafine (Lamisil)?

From the Guidelines

Terbinafine can cause several side effects, including common ones like headache, diarrhea, rash, and changes in taste sensation, as well as more serious but less common side effects like liver problems and severe skin reactions, as reported in the most recent study 1.

Common Side Effects

• Headache
• Diarrhea
• Rash
• Changes in taste sensation (dysgeusia) Some patients may experience stomach discomfort, nausea, or mild skin reactions.

Serious Side Effects

More serious but less common side effects include:

• Liver problems (which may present as yellowing of the skin or eyes, dark urine, or abdominal pain)
• Severe skin reactions
• Blood disorders
• Depression Terbinafine can also rarely cause Stevens-Johnson syndrome or toxic epidermal necrolysis, which are life-threatening skin conditions.

Monitoring and Precautions

Patients should immediately report any signs of allergic reaction such as hives, difficulty breathing, or swelling of the face, lips, tongue, or throat. It's essential to complete the full course of treatment as prescribed, which is typically 6 weeks for fingernail infections and 12 weeks for toenail infections, as recommended in the guidelines 1. These side effects occur because terbinafine works by inhibiting the enzyme squalene epoxidase in fungi, but this mechanism can also affect human cells, particularly in the liver where the medication is metabolized. Patients with pre-existing liver disease or kidney problems should use terbinafine with caution and may require dose adjustments or more frequent monitoring, as suggested in the study 1. Baseline liver function tests and a complete full blood count are recommended in adult patients with a history of hepatotoxicity or haematological abnormalities, as stated in the guidelines 1.

From the FDA Drug Label

What are the possible side effects of terbinafine? Terbinafine may cause serious side effects, including: liver problems that can lead to the need for liver transplant, or death. The most common side effects of terbinafine include: headache, diarrhea, rash, dyspepsia, liver enzyme abnormalities, pruritus, taste disturbance, nausea, abdominal pain, and flatulence.

Terbinafine side effects may include:

• Serious side effects: liver problems, death
• Common side effects:
  • headache
  • diarrhea
  • rash
  • dyspepsia
  • liver enzyme abnormalities
  • pruritus
  • taste disturbance
  • nausea
  • abdominal pain
  • flatulence 2 2

From the Research

Terbinafine Side Effects

• Terbinafine has been associated with several side effects, including severe liver injury and cutaneous adverse reactions 3, 4.
• The symptoms of terbinafine-induced severe liver injury include jaundice, flu-like symptoms, dark urine, and pruritus, with a mean duration of treatment until onset of symptoms of 30.2 days 3.
• Cutaneous adverse effects associated with terbinafine therapy include erythema multiforme, erythroderma, severe urticaria, pityriasis rosea, and worsening of pre-existing psoriasis 4.
• Severe drug eruptions have also been reported, highlighting the importance of considering the risk of adverse reactions when prescribing terbinafine, especially for mild conditions such as onychomycosis 5.
• Patients should be advised to discontinue treatment and seek medical attention if symptoms of liver injury or cutaneous adverse reactions occur 3, 4.
• The timeline of severe liver injury onset varies significantly, but most cases occur between 4 and 6 weeks after starting treatment 3.