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Pharmacology · Azole antifungals

Clotrimazole !

Imidazole antifungal used on the skin, in the vagina and as a mouth lozenge for Candida and ringworm. Very little reaches the blood.

Updated 2026-11-01

  • Class: Azole antifungals
  • Enzyme: Lanosterol 14α-demethylase (CYP51, the fungal ERG11 enzyme)
  • ATC code: G01AF02
  • WHO Model List of Essential Medicines

The figure shows clotrimazole bound to CYP51 from the amoeba Acanthamoeba castellanii; the fungal enzyme has the same sterol-demethylase site.

Target in 3D: Lanosterol 14α-demethylase (CYP51, the fungal ERG11 enzyme). PDB structure 6UW2 (RCSB PDB, public domain). View the structure at RCSB PDB

Mechanism of action

Clotrimazole inhibits the sterol 14α-demethylase of yeasts and dermatophytes and alters the permeability of the fungal membrane. It is fungistatic at usual concentrations and may be fungicidal against Candida at higher ones.

  1. Clotrimazole blocks the fungal sterol demethylase
  2. The membrane loses ergosterol and becomes leaky
  3. Yeast and dermatophyte growth stops where it is applied

Pharmacokinetics

Absorption
Minimal: lozenges give very low blood levels; a small fraction of a vaginal dose is absorbed.
Distribution
After a lozenge dissolves, active levels persist in saliva for a few hours, released slowly from the oral mucosa.

Indications

Adverse effects

Common

  • Lozenges: nausea, vomiting, unpleasant mouth sensation, itching
  • Lozenges: mildly raised AST
  • Vaginal: burning, itching or irritation
  • Skin: redness, stinging, peeling

Contraindications

  • Hypersensitivity to any component
  • Lozenges are not for systemic mycoses

Key interactions

Latex condoms and diaphragms
Vaginal clotrimazole can weaken them, so they may fail to prevent pregnancy or sexually transmitted infections.

What is monitored

  • Clinical response of the lesions
  • Liver tests periodically with long lozenge use

Administration and safety

  • Lozenges must dissolve slowly in the mouth, without chewing, crushing or swallowing them; the patient must be able to follow this.
  • Confirm oral candidiasis with a KOH smear or culture before treatment.
  • Vaginal forms: warn that latex condoms and diaphragms may fail during treatment.

Nursing care

  • Inspect the mouth, skin or vulva before and during treatment.
  • Teach to complete the course even if symptoms fade.
  • Vaginal yeast infection does not cause fever, pelvic pain or foul discharge: those need medical review.

Pregnancy and breastfeeding

Embryotoxic in animals only at oral exposures far above human use and not teratogenic; lozenges are used in pregnancy only if the benefit justifies the risk.

Test yourself

Think of the answer, then tap the question to see it.

How must clotrimazole lozenges be taken to work?

Dissolved slowly in the mouth so that the drug coats the mucosa and stays in the saliva.

What contraceptive warning goes with vaginal clotrimazole?

It can weaken latex condoms and diaphragms, which may then fail.

Is clotrimazole an imidazole or a triazole?

An imidazole, like miconazole and ketoconazole.

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Educational content on how drugs work; not a prescribing guide and no substitute for a health professional's advice. No doses are given.

Sources: DailyMed - CLOTRIMAZOLE lozenge (DailyMed (U.S. National Library of Medicine), 2025); Clotrimazole Vaginal: MedlinePlus Drug Information (MedlinePlus (U.S. National Library of Medicine), 2023); Clotrimazole Topical: MedlinePlus Drug Information (MedlinePlus (U.S. National Library of Medicine), 2018); Goodman & Gilman's The Pharmacological Basis of Therapeutics, 14th ed., ch. 61 (McGraw Hill, 2023).

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Representative model, for educational purposes only.