Drug Guide
Cantharidin
Classification
Therapeutic: Antineoplastic agent (used topically, off-label for molluscum contagiosum)
Pharmacological: Vesicant (blistering agent)
FDA Approved Indications
- Off-label use for molluscum contagiosum, primarily as a topical blistering agent. Not FDA-approved for systemic use.
Mechanism of Action
Cantharidin induces blister formation by causing epidermal cell desquamation through the disruption of cell adhesion, leading to local blistering and the removal of lesions.
Dosage and Administration
Adult: Application of a small amount to the lesion, typically once, under medical supervision. Precise dosing depends on the lesion size and location.
Pediatric: Used cautiously under medical supervision; dosage similar to adults but adjusted based on lesion size and patient tolerance.
Geriatric: Use with caution; monitor for enhanced skin reactions.
Renal Impairment: Not well-studied; caution advised.
Hepatic Impairment: Not well-studied; caution advised.
Pharmacokinetics
Absorption: Minimal systemic absorption when applied topically.
Distribution: Predominantly localized at the site of application.
Metabolism: Metabolized locally in the skin; systemic metabolism not significant.
Excretion: Excreted primarily via local skin exfoliation.
Half Life: Not applicable due to topical use.
Contraindications
- Allergy to cantharidin or blistering agents.
- Open wounds or infected skin at application site.
Precautions
- Use with caution in sensitive skin, and avoid application to mucous membranes or genitals due to risk of injury.
- Not for use in pregnant or breastfeeding women without medical advice; safety data is limited.
Adverse Reactions - Common
- Local blistering, erythema (Common)
- Pain at application site (Common)
Adverse Reactions - Serious
- Infection, scarring, ulceration (Rare)
- Allergic contact dermatitis (Rare)
Drug-Drug Interactions
- None well-documented for systemic interactions.
Drug-Food Interactions
- None specific.
Drug-Herb Interactions
- Caution with herbs that affect skin healing or cause dermatitis, e.g., calendula, St. John's Wort.
Nursing Implications
Assessment: Assess skin integrity and description of lesion size and location.
Diagnoses:
- Risk for infection related to skin barrier disruption.
Implementation: Apply under strict medical supervision; educate caregivers on application technique and potential reactions.
Evaluation: Monitor for lesion resolution, adverse reactions, and signs of infection or scarring.
Patient/Family Teaching
- Inform about the blistering effect and expected skin response.
- Advise on care of the treated area, including keeping it clean and dry.
- Warn about signs of excessive pain, infection, or adverse reactions.
Special Considerations
Black Box Warnings:
- None currently approved or mandated.
Genetic Factors: None established.
Lab Test Interference: None known.
Overdose Management
Signs/Symptoms: Localized blistering, pain, possible secondary infection.
Treatment: Supportive care; wound management; hospitalization if extensive tissue damage occurs.
Storage and Handling
Storage: Store at room temperature, away from children.
Stability: Stable under normal storage conditions.