Is terbinafine (antifungal medication) safe during pregnancy and lactation?

Terbinafine Safety in Pregnancy and Lactation

Terbinafine should be avoided during pregnancy when possible, but can be considered for topical use in limited areas for brief periods; it should be used with caution during lactation as it passes into breast milk. 1, 2

Pregnancy Considerations

Safety Profile

• Terbinafine is classified as FDA Pregnancy Category B, indicating that animal reproduction studies have not shown fetal risk, but adequate controlled studies in pregnant women are lacking 1, 2
• The Infectious Diseases Society of America guidelines specifically state that pregnant women with fungal infections should not receive azole therapy due to teratogenic potential, but note that terbinafine "is not expected to harm an unborn baby" 1
• However, the FDA label recommends that terbinafine not be initiated during pregnancy because:
  • Treatment of onychomycosis can typically be postponed until after pregnancy
  • There are no adequate well-controlled studies in pregnant women 2

Recent Evidence

• A 2022 systematic review found no increased risk of congenital malformations, spontaneous abortion, preterm birth, or other adverse pregnancy outcomes following systemic or topical terbinafine exposure during pregnancy 3
• A 2020 nationwide registry-based cohort study in Denmark (1,650,649 pregnancies) showed:
  • No increased risk of major malformations with oral terbinafine (prevalence odds ratio 1.01,95% CI 0.63-1.62)
  • No increased risk of spontaneous abortion with oral terbinafine (hazard ratio 1.06,95% CI 0.86-1.32) 4

Application Method Considerations

• Topical terbinafine appears to have a better safety profile in pregnancy due to limited systemic absorption 5
• For topical antifungal medications in pregnancy, clotrimazole, miconazole, and nystatin are considered first-line agents
• Topical terbinafine may be utilized as a second-line agent when first-line options are ineffective 5

Lactation Considerations

• The FDA label states that terbinafine is present in breast milk with a milk-to-plasma ratio of 7:1 2
• Treatment with terbinafine is not recommended in nursing mothers according to the FDA label 2
• The Infectious Diseases Society of America notes that terbinafine passes into breast milk and "could have an effect on a nursing baby" 1

Clinical Decision Making

When to Consider Terbinafine in Pregnancy

1. For non-urgent fungal infections (e.g., onychomycosis):

   • Postpone treatment until after pregnancy when possible 1, 2
   • Consider topical alternatives like clotrimazole or miconazole first 5

2. For urgent fungal infections requiring treatment:

   • For cutaneous or lymphocutaneous sporotrichosis:
     • Local hyperthermia is an option during pregnancy 1
     • Amphotericin B is recommended for life-threatening infections 1

When to Consider Terbinafine in Lactation

• Avoid if possible due to high concentration in breast milk (7:1 milk-to-plasma ratio) 2
• Discuss risks and benefits with patients if treatment is necessary 1
• Consider temporary interruption of breastfeeding during treatment period

Common Pitfalls to Avoid

1. Assuming all antifungal medications carry similar risks in pregnancy
2. Failing to consider the urgency of treatment versus potential risks
3. Not exploring topical alternatives when appropriate
4. Overlooking the high concentration of terbinafine in breast milk
5. Initiating treatment for non-urgent conditions like onychomycosis during pregnancy when it can be safely postponed

Remember that while recent evidence suggests terbinafine may be safer than previously thought in pregnancy, the official FDA recommendation still advises against initiating treatment during pregnancy when it can be postponed until after delivery.