Ciclopirox

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Cat Number

API0232283

CAS Number

29342-05-0

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CAS Number

29342-05-0

EINECS

249-577-2

Storage

Store at room temperature

Synonyms

Loprox; Penlac; Ciclopiroxum; HOE 296b; 2(1H)-Pyridinone, 6-cyclohexyl-1-hydroxy-4-methyl-; cyclopirox

Molecular Formula

C12H17NO2

Molecular Weight

207.27

Smiles

CC1=CC(=O)N(C(=C1)C2CCCCC2)O

Appearance

white to off-white solid

Melting Point

144°C

Boiling Point

350.0±25.0°C at 760 mmHg (Predicted)

Relative Density

1.193±0.06 (Predicted)

General Description

Ciclopirox is a synthetic hydroxypyridone derivative with a cyclohexyl group and a methyl group, belonging to the class of antifungal agents. Its chemical structure is 6-cyclohexyl-1-hydroxy-4-methylpyridin-2-one. Ciclopirox is a white to off-white crystalline powder, practically insoluble in water but soluble in organic solvents. The molecule is a chelating agent that binds to metal ions.

Mechanism of Action

Ciclopirox exerts its antifungal activity by chelating metal ions, such as iron and copper, which are essential cofactors for many fungal enzymes. This disrupts the activity of metal-dependent enzymes, including catalase and peroxidase, leading to oxidative damage and cell death. The drug also inhibits the synthesis of fungal cell membrane components and interferes with the uptake of amino acids and nutrients.

Application

Ciclopirox is indicated for the topical treatment of tinea pedis (athlete's foot), tinea cruris (jock itch), tinea corporis (ringworm), and cutaneous candidiasis. It is also used for the treatment of seborrheic dermatitis and for the management of nail infections. The drug is effective against a wide range of dermatophytes and yeasts, and is generally well-tolerated.

This review summarizes the anticancer potential of ciclopirox (CPX), a broad-spectrum antifungal drug. Preclinical and clinical data support that systemic CPX is feasible and safe. CPX exerts anticancer effects through multiple mechanisms largely via iron chelation, inhibiting proliferation, inducing apoptosis, suppressing migration/invasion, and blocking angiogenesis/lymphangiogenesis. Five patents have been filed, mostly for prodrugs to improve solubility and bioavailability. CPX has great potential for repurposing as a cancer therapeutic.

Fig. 1 Ciclopirox inhibits multiple signaling molecules related to cancer development and progression. (Huang Z, and Huang S, 2021)

References

Huang Z, Huang S. Reposition of the Fungicide Ciclopirox for Cancer Treatment. Recent Pat Anticancer Drug Discov. 2021;16(2):122-135.

Ciclopirox (CPX), an FDA‑approved antifungal, inhibited vaccinia, cowpox, and monkeypox virus replication in vitro with EC₅₀ in the sub‑micromolar range. It acts primarily through chelation of intracellular Fe³⁺, as shown by rescue with ferric ammonium citrate and by overexpression of iron‑dependent enzymes. CPX also reduced VACV titers in ex vivo mouse lung tissue. Host iron metabolism is a critical determinant of poxvirus replication, making CPX a promising antiviral candidate.

Fig. 2 CPX inhibits VACV replication without affecting host cell viability. (Pant A, et al., 2025)

References

Pant A, et al. Ciclopirox suppresses poxvirus replication by targeting iron metabolism. Antiviral Res. 2025;244:106290.

Does Ciclopirox require protection from light during long‑term storage?

Yes, it is photosensitive. UV exposure can cause photodegradation and discoloration of the pyridone ring. Store in light‑resistant containers, preferably amber glass.

What is the recommended storage temperature for Ciclopirox?

Store at controlled room temperature (15–25°C). Avoid excessive heat above 30°C, which can soften the powder and accelerate degradation.

Is Ciclopirox stable in topical cream and solution formulations?

Yes, when formulated with preservatives and protected from light.

How is the impurity ciclopirox N‑oxide (an oxidative degradation product) monitored?

This degradation product is quantified using a stability‑indicating HPLC method, ensuring it remains within pharmacopoeial limits.