cantharidin topical (Rx)

>10%

Mild

• Vesicles (60%)
• Pruritus (47%)
• Pain (41%)
• Scab (39%)
• Discoloration (28%)
• Erythema (24%)
• Dryness (19%)

Moderate

• Vesicles (32%)
• Erythema (21%)
• Pain (20%)

1-10%

Mild

• Edema (7%)
• Erosion (6%)

Moderate

• Scab (9%)
• Pruritus (8%)
• Discoloration (4%)
• Edema (3%)
• Dryness (2%)
• Erosion (1%)
• Contact dermatitis (1%)

Severe

• Vesicles (4%)
• Pain (2%)
• Pruritus (1%)

<1%

Severe

• Application site erythema
• Application site discoloration

Contraindications

None

Cautions

Toxicities associated with inappropriate administration

• Life threatening or fatal toxicities can occur if administered orally
• Avoid contact with treatment area, including oral contact, after treatment
• Oral ingestion may result in renal failure, blistering and severe damage to gastrointestinal tract, coagulopathy, seizures, and flaccid paralysis
• Ocular toxicity can occur if cantharidin comes in contact with eyes; if this occurs, flush eyes with water for at least 15 minutes
• Contact with eyes can result in corneal necrosis, ocular perforation, and deep ocular injuries
• Advise patients and/or caregivers to avoid oral and eye contact, and to avoid touching lesions after treatment; seek medical attention immediately if accidently ingested

Local skin reactions

• Application site reactions reported, including vesiculation, pruritus, pain, discoloration, and erythema
• Avoid application near eyes and mucosal tissue, and to healthy skin
• Immediately remove solution by wiping with cotton swab or gauze if contact with unintended surface or healthy skin occurs
• Avoid other topical products (eg, creams, lotions, sunscreen) on treated areas until 24 hr after treatment or until washing
• Application of other topical products could spread cantharidin and cause blistering or other adverse reactions to healthy skin
• If severe blistering, severe pain, or other severe adverse reactions occur, remove cantharidin before recommended 24 hr treatment period by washing with soap and water

Flammability

• Solution is flammable, even after drying
• Avoid fire, flame, or smoking near lesion(s) during treatment and after application until removed

Pregnancy

There are no available data with use in pregnant females to evaluate for drug-associated risk of major birth defects, miscarriage, or adverse maternal or fetal outcomes

Animal reproduction studies were not conducted

Systemic exposure following topical cantharidin administration is low; maternal use not expected to result in fetal exposure to the drug

Lactation

Avoid application to areas with increased risk for potential ingestion by or ocular exposure to breastfeeding child

There are no data on presence of cantharidin in either human or animal milk, or effects on breastfed infants, or on milk production

Breastfeeding is not expected to result in cantharidin exposure to child owing to low systemic absorption following topical administration

Consider developmental and health benefits of breastfeeding along with the clinical need for cantharidin and any potential adverse effects on breastfeeding children from cantharidin or from the underlying maternal condition

Pregnancy Categories

A: Generally acceptable. Controlled studies in pregnant women show no evidence of fetal risk.

B: May be acceptable. Either animal studies show no risk but human studies not available or animal studies showed minor risks and human studies done and showed no risk.

C: Use with caution if benefits outweigh risks. Animal studies show risk and human studies not available or neither animal nor human studies done.

D: Use in LIFE-THREATENING emergencies when no safer drug available. Positive evidence of human fetal risk.

X: Do not use in pregnancy. Risks involved outweigh potential benefits. Safer alternatives exist.

NA: Information not available.

Mechanism of Action

Mechanism of action is unknown in the treatment of molluscum contagiosum

Cantharidin is absorbed by lipids in the membrane of epidermal keratinocytes, where it activates the release of neutral serine protease enzymes

These enzymes subsequently break peptide bonds in surrounding proteins, leading to progressive degeneration of desmosomal dense plaques, which are important cellular structures that participate in cell-to-cell adhesion

Degeneration results in detachment of tonofilaments that hold cells together, thereby leading to selective acantholysis (loss of cellular connections) and skin blistering when applied topically

Absorption

Plasma levels not detectable in 15 of 16 individuals following single application (average lesions treated 47.4)

1 of 16 had detectable plasma level of 3.391 ng/mL 2-hr post-dose

Topical Preparation

Instruct and train all healthcare professionals before preparation and administration

Use nitrile or vinyl gloves and eye protection during preparation and administration

See prescribing information for full instructions and diagrams

Use of applicator and break tool

• Do not reuse the applicator
• Applicator is for single treatment session only
• Do not attempt to use a clogged applicator
• Do not cut or modify applicator in any way; doing so could reduce dispensing control
• Do not remove applicator cap before breaking glass ampule
• If any damage or leaks are observed on applicator or break tool, discard applicator in a sharps container and handle in accordance with accepted medical practice and applicable law

Topical Administration

Applied topically by clinician

Not for oral, mucosal, or ophthalmic use

Clinician administration

• See prescribing information for full instructions and diagrams
• Use nitrile or vinyl gloves and eye protection during preparation and administration
• Apply topically as a single application to cover each lesion; allow solution to completely dry (up to 5 minutes) before contacting healthy skin to avoid transference
• Not to exceed 2 cantharidin applicators/single treatment session
• Administer every 3 weeks as needed
• Do not cover any treated lesions with bandages
• If cantharidin contacts any unintended surface, including healthy skin, immediately remove by wiping with a cotton swab or gauze

Patient instructions

• Avoid contact with the treatment area, including oral contact, after application
• Do not apply near eyes
• Remove with soap and water 24 hr after treatment
• If severe blistering, severe pain, or other severe adverse reactions occur, remove with soap and water prior to 24 hours after treatment
• Avoid other topical products on treated areas until 24 hr after treatment or until washing
• Avoid fire, flame, or smoking near lesion(s) during treatment

Storage

Store at 20-25ºC (68-77ºF); excursions permitted to 15-30ºC (59-86ºF)

Protect from light