Do I need to get Liver Function Tests (LFTs) before starting antifungal tablets, even for a short course, if I have no known liver disease or abnormal liver function tests?

Liver Function Testing Before Starting Antifungal Tablets

For short courses of oral antifungal therapy in patients with no known liver disease, baseline liver function tests are not routinely required before starting treatment.

Evidence-Based Approach to LFT Monitoring with Antifungals

Risk Assessment for LFT Monitoring

The need for liver function testing before starting antifungal therapy depends on several factors:

1. Duration of therapy:

   • Short courses (typically 1-2 weeks): Generally do not require baseline LFTs in patients without risk factors
   • Longer courses: Baseline LFTs recommended

2. Patient risk factors:

   • Baseline LFTs recommended if:
     • History of liver disease
     • Abnormal previous LFTs
     • Concurrent hepatotoxic medications
     • Excessive alcohol consumption
     • Viral hepatitis
     • Family history of heritable liver disease 1

3. Type of antifungal:

   • Azoles (fluconazole, itraconazole): Higher risk of hepatotoxicity
   • Terbinafine: Lower risk but still can cause hepatotoxicity

Monitoring Recommendations by Drug Class

Azole Antifungals

• Fluconazole: FDA label states it "should be administered with caution to patients with liver dysfunction" and has been associated with "rare cases of serious hepatic toxicity" 2
• Itraconazole: The British Association of Dermatologists recommends monitoring hepatic function tests in patients:
  • With pre-existing abnormal results
  • Receiving continuous therapy for more than a month
  • Taking concomitant hepatotoxic drugs 1

Terbinafine

• Baseline liver function tests recommended in patients with:
  • History of heavy alcohol consumption
  • Hepatitis
  • Hematological abnormalities 1
• Not recommended in patients with active or chronic liver disease

Practical Approach Based on Treatment Duration

For Short-Course Therapy (1-2 weeks):

• No known liver disease or risk factors: No baseline LFTs required
• With liver disease or risk factors: Obtain baseline LFTs

For Extended Therapy (>2 weeks):

• Baseline LFTs recommended for all patients
• Regular monitoring during treatment (typically every 2-4 weeks initially, then every 1-3 months) 1

Clinical Considerations and Pitfalls

Common Pitfalls to Avoid

1. Over-testing in low-risk patients on short courses
2. Under-monitoring in high-risk patients or those on prolonged therapy
3. Failing to recognize early signs of hepatotoxicity (nausea, fatigue, right upper quadrant pain)

Important Caveats

• Antifungal-induced liver injury can occur without warning symptoms
• Hepatotoxicity from antifungals is typically reversible upon discontinuation 3
• The risk of clinically significant hepatotoxicity from short-course antifungal therapy in patients without liver disease is very low

When to Stop or Modify Therapy

• Discontinue antifungal if:
  • ALT increases to >10 times upper limit of normal
  • ALT elevation accompanied by signs of liver inflammation
  • Clinical signs of liver disease develop 1

In conclusion, while antifungals can cause hepatotoxicity, the risk with short-course therapy in patients without liver disease is minimal. Focus monitoring efforts on high-risk patients and those receiving prolonged therapy.