What is the difference between metronidazole (antibiotic) and fluconazole (antifungal) in terms of their uses and dosages?

From the Guidelines

Metronidazole and fluconazole are not the same, as they target different types of infections and have distinct mechanisms of action and dosing regimens. Metronidazole is an antibiotic that treats bacterial and protozoal infections, particularly anaerobic bacteria, Trichomonas, Giardia, and Entamoeba, with common prescriptions including bacterial vaginosis (500mg twice daily for 7 days), trichomoniasis (2g single dose), Clostridium difficile infections (500mg three times daily for 10-14 days), and anaerobic infections (500mg every 8 hours) 1. Fluconazole, in contrast, is an antifungal medication that treats fungal infections by inhibiting ergosterol synthesis in fungal cell membranes, used for vaginal candidiasis (150mg single dose), oropharyngeal candidiasis (200mg first day, then 100mg daily for 1-2 weeks), and systemic fungal infections (400mg first day, then 200-400mg daily for weeks to months depending on infection severity) 1. The medications differ in their mechanisms of action: metronidazole damages bacterial DNA after being reduced by anaerobic organisms, while fluconazole disrupts fungal cell membrane integrity. Both medications can cause gastrointestinal side effects, but metronidazole has a distinctive metallic taste and alcohol interaction, while fluconazole has more potential for drug interactions through the cytochrome P450 system. Key differences in their use are:

• Indications: Metronidazole for bacterial and protozoal infections, Fluconazole for fungal infections
• Mechanism of action: Metronidazole damages bacterial DNA, Fluconazole disrupts fungal cell membrane integrity
• Dosage: Varies by infection type and severity for both medications
• Side effects: Both can cause gastrointestinal issues, but metronidazole has a metallic taste and alcohol interaction, while fluconazole has more drug interactions. Given the most recent and highest quality evidence, the choice between metronidazole and fluconazole should be based on the specific type of infection being treated, with metronidazole used for bacterial and protozoal infections and fluconazole used for fungal infections 1.

From the Research

Difference between Metronidazole and Fluconazole

• Metronidazole is an antibiotic used to treat various infections caused by bacteria and protozoa, such as trichomoniasis, amoebiasis, and giardiasis 2, 3.
• Fluconazole is an antifungal medication used to treat fungal infections, including vulvovaginal candidiasis and other types of candidiasis 4, 5, 6.

Uses of Metronidazole and Fluconazole

• Metronidazole is used to treat:
  • Anaerobic bacterial infections
  • Trichomoniasis
  • Amoebiasis
  • Giardiasis
  • Vaginosis due to Gardnerella vaginalis 2, 3
• Fluconazole is used to treat:
  • Vulvovaginal candidiasis
  • Other types of candidiasis
  • Fungal infections in immunocompromised patients 4, 5, 6

Dosages of Metronidazole and Fluconazole

• Metronidazole dosages vary depending on the infection being treated, but typical dosages range from 500mg to 2000mg per day 3.
• Fluconazole dosages also vary depending on the infection being treated, but typical dosages range from 50mg to 400mg per day 4, 6.
• In the treatment of recurrent vulvovaginal candidiasis, a combined scheme of fluconazole 200mg and metronidazole 500mg with clotrimazole 100mg has been proposed 4.