Nearly 50% of women’s healthcare providers have reported fluconazole resistance in their patients, but there are few reports of miconazole-resistant C. albicans species, even though this treatment has been widely used for the past 4 decades.3,6 This suggests that first-line treatment with miconazole, the active ingredient in MONISTAT®, remains appropriate, particularly in certain patient populations.

In a study looking at MIC90 trends from 1986 – 2007 for 250 C. albicans vaginal isolates3:

  • Miconazole: MIC90 unchanged (0.06 μg/mL)
    • Percent isolates with MIC90 ≥ 0.5 μg/mL increased from 2% to 9% during this period but since this is a topical agent and vaginal fluid levels exceed 10 μg/mL, resistance is unlikely to be an issue

MONISTAT® (miconazole) Resistance Chart

Evolution and selection of vaginal-colonizing Candida species with reduced susceptibility could play a critical early role in the development of antifungal resistance among C. albicans isolates responsible for refractory candidiasis.3

  • Fluconazole MIC90: 0.25 μg/mL → 0.5 μg/mL
    • Percent isolates with MIC90 ≥ 1 μg/mL and ≥ 2 μg/mL both increased from 3% to 9% over this period
    • While not a clinically significant MIC90 increase, the increase in isolates with elevated MIC90 may have clinical relevance given the achievable concentrations of fluconazole in vaginal fluid (maximum 2 μg/mL)

Fluconazole Resistance Chart

Fluconazole use has increased dramatically over time

fluconazole Prescriptions Over Time

Routine use of prescription oral fluconazole may create an environment where non-albicans Candida, which are less susceptible to azoles, thrive and spread in the vagina.

  • Oral fluconazole achieves low tissue concentration at the site of infection while the rest remains in systemic circulation.
  • A significant amount of the drug remains in the GI tract, reducing C. albicans but allowing less-susceptible non-albicans species to grow.
  • These non-albicans species reach the vagina and are more likely to be resistant to fluconazole treatment.

Repeat systemic antifungal therapy perpetuates drug-resistant species.