Ycanth - Drug Monograph

Introduction

Ycanth (cantharidin) is a topical vesicant solution approved by the FDA for the treatment of molluscum contagiosum. This blistering agent has been used in dermatology for decades but received formal FDA approval in 2023 for a specific proprietary formulation. Ycanth represents the first FDA-approved prescription treatment for molluscum contagiosum, a common viral skin infection that primarily affects children.

Mechanism of Action

Cantharidin, the active ingredient in Ycanth, is a vesicant substance derived from blister beetles (Cantharis vesicatoria). It works through several mechanisms:

• Induces acantholysis (separation of epidermal cells) by inhibiting protein phosphatases
• Causes epidermal cleavage at the stratum spinosum level through disruption of desmosomes
• Creates intraepidermal blisters by stimulating protease activity
• Triggers an inflammatory response that may enhance immune recognition of the viral lesions

The blister formation effectively destroys the infected epidermal cells containing molluscum contagiosum virus, while potentially stimulating a localized immune response against the virus.

Indications

Ycanth is FDA-approved for:

• Topical treatment of molluscum contagiosum in adult and pediatric patients 2 years of age and older

It is specifically indicated for the treatment of clinically typical, non-genital molluscum contagiosum lesions.

Dosage and Administration

• Apply topically to molluscum contagiosum lesions once every 3 weeks
• Maximum treatment area: 20 cm² per session
• Maximum volume: 0.8 mL per session

1. Clean and dry the treatment area before application 2. Apply a thin layer to completely cover each lesion 3. Allow solution to dry completely (approximately 2 minutes) 4. Wash hands thoroughly after application 5. Do not cover with occlusive dressings unless directed by healthcare provider

• Pediatric patients: Approved for children ≥2 years; use smallest effective amount
• Geriatric patients: No specific dosage adjustment recommended
• Renal/hepatic impairment: No formal studies; use with caution

Pharmacokinetics

Contraindications

• Hypersensitivity to cantharidin or any component of the formulation
• Application to genital molluscum lesions (not studied)
• Application to mucosal surfaces (eyes, mouth, nose)
• Use on broken or inflamed skin
• Patients with known glucose-6-phosphate dehydrogenase (G6PD) deficiency

Warnings and Precautions

• Localized pain and discomfort
• Potential scarring or hypopigmentation
• Secondary bacterial infection if not properly managed

• Hematuria
• Gastrointestinal disturbances
• Renal irritation (with excessive application)

• Pregnancy: Category C - Use only if potential benefit justifies potential risk
• Lactation: Exercise caution; avoid application to breast area
• Immunocompromised patients: Safety and efficacy not established

Drug Interactions

No formal drug interaction studies have been conducted. However, theoretical interactions include:

• Other topical medications: Potential for increased irritation or altered absorption
• Systemic corticosteroids: May impair immune response to treatment
• Topical immunosuppressants: May interfere with desired inflammatory response

Adverse Effects

• Application site pain (82%)
• Application site vesicles (42%)
• Application site pruritus (35%)
• Application site erythema (32%)
• Application site scabbing (28%)
• Application site discoloration (15%)

• Severe blistering reactions
• Secondary bacterial infections
• Hypersensitivity reactions
• Scarring or permanent pigment changes

Monitoring Parameters

• Treatment response: Lesion resolution at follow-up visits
• Local reactions: Blister formation, pain, signs of infection
• Skin changes: Pigment alterations, scarring
• Systemic symptoms: Especially in cases of overapplication (urinary changes, abdominal pain)
• Adherence to application instructions: Proper technique and safety precautions

Patient Education

• Use only as directed by healthcare provider
• Apply only to affected areas identified by your provider
• Allow solution to dry completely before covering with clothing
• Wash hands thoroughly after application

• Blistering within 24-48 hours after application
• Mild to moderate pain at treatment sites
• Scabbing and healing over 1-2 weeks
• Possible temporary skin color changes

• Avoid contact with eyes, mouth, and genital areas
• Do not apply to broken or inflamed skin
• Keep out of reach of children and pets
• Do not share medication with others

• Severe pain or blistering
• Signs of infection (increased redness, pus, fever)
• Spread of lesions to untreated areas
• Systemic symptoms (blood in urine, abdominal pain)

References

1. FDA Approval Package: Ycanth (cantharidin) topical solution. FDA.gov. 2023. 2. Browning JC, Cartwright M, et al. Efficacy and safety of topical cantharidin treatment for molluscum contagiosum. Pediatr Dermatol. 2022;39(4):555-561. 3. van der Wouden JC, van der Sande R, et al. Interventions for cutaneous molluscum contagiosum. Cochrane Database Syst Rev. 2017;5:CD004767. 4. Silverberg NB, Sidbury R, Mancini AJ. Childhood molluscum contagiosum: Experience with cantharidin therapy in 300 patients. J Am Acad Dermatol. 2000;43(3):503-507. 5. Product Monograph: Ycanth™ (cantharidin) topical solution. Verrica Pharmaceuticals Inc. 2023. 6. Berger EM, Orlow SJ, et al. Practice patterns in the treatment of molluscum contagiosum. Pediatr Dermatol. 2021;38(2):385-390.