Indications And Clinical Uses: For the topical use of removal of benign epithelial growths such as warts (verruca vulgaris) or molluscum contagiosum. Because of the absence of scarring, cantharidin is useful for treating exposed areas where cosmetic results are important. Painless application and the absence of instruments makes it especially useful for treating children.
Contra-Indications: Hypersensitivity to the ingredients. Avoid alcoholic beverages for several hours after treatment.
Precautions: Cantharidin is a potent vesicant and is to be applied only by the physician. It is recommended care be used in the selection of patients to be treated and method used. The physician should develop his own experience and technique. Care should be used in selection of site of application since residual pigmentation may occur (rarely). It is recommended patients be advised of effect and possible results of treatment. Do not use on mucosal tissue. Do not use if growth or surrounding tissue is inflamed or irritated. Do not use on diabetics, or people with poor blood-circulation, on moles, birthmarks, or unusual warts with hair growing from them. Larger areas should not be treated at one time since discomfort may be excessive and systemic absorption may result.
Pregnancy and Lactation: Use during pregnancy or in nursing mothers is not recommended since there have been no adequate and well controlled studies performed in these groups.
Adverse Reactions: The development of annular warts following therapy has been reported in a small percentage of patients when the method of treatment was not properly followed. These lesions are superficial and, although they may alarm some patients, present little problem. Treatment consists of patient reassurance and re-treatment using either cantharidin or other procedures. There has been 1 report of chemical lymphangitis following use in combination with salicylic acid plaster.
Dosage And Administration: Without Curettage: No cutting or prior treatment is required. (Occasionally nails must be trimmed to expose subungual warts to medication.) Using a Q-Tip or applicator stick, apply cantharidin (1 layer only) to the wart and a 1 to 3 mm margin around the wart. Allow to dry for a few minutes. Cover with a piece of non-porous plastic adhesive tape. Instruct patient to keep the tape on for at least 4 hours (up to 24 hours). Within 24 hours a blister forms which is often painful and inflamed. Have the patient return for observation in 1 week. Remove necrotic tissue and treat as before if any viable wart tissue remains. Allow tissue to re-epithelialize before re-treatment.
With Curettage: Proceed as without curettage except have patient return in 1 day for curettage. (Local anesthesia may be necessary.) Advantages to this method include: Treatment prior to curettage enhances identification of tissue planes, increases separability of wart tissue and re-treatment is rarely necessary. Have the patient return for observation in 4 weeks. (The lesion normally heals completely within 1 to 3 weeks.) The use of a mild antibacterial agent until area heals is recommended.
Plantar Warts: Pare away keratin covering the wart, avoid bleeding. Using a Q-Tip or applicator stick, apply cantharidin to both the wart and a 1 to 3 mm margin around the wart. Allow a few minutes to dry. Secure with non-porous plastic adhesive tape. Leave in place for 1 week, then debride. If any viable wart tissue remains after debridement, re-apply a small amount of cantharidin and bandage as above. Three or more such treatments may be required for large lesions. When destruction of wart is complete, the healed site will appear smooth, with normal skin lines.
Palpebral Warts: Using a toothpick or fine probe, apply a small amount of cantharidin to the surface of the wart. Make certain that film is thoroughly dry. Avoid touching surrounding normal skin or applying inside the eye lashes. Leave lesion uncovered. Patient should be warned not to touch the eyelid. Removal of necrotic material should be done by the doctor. Repeat in a week or ten days if any growth remains and area is free of irritation or inflammation. After the removal of the growth, the use of a mild bacterial until area heals is advisable.
Molluscum contagiosum: Coat each lesion with a thin film of cantharidin. After 1 week, treat any new lesions the same way and re-treat any resistant lesions, covering with a small piece of occlusive tape. The tape should be removed in 6 to 8 hours.
Warn the patient that the blister may be painful. A mild analgesic, e.g. ASA with codeine, or acetaminophen with codeine may be used. The tape may be removed and the area soaked in cool water for 10 to 15 minute periods, as needed, provided sufficient time has been allowed for the medication to penetrate. Local anesthesia may be needed during curettage.
Note: Cantharidin is a strong vesicant and may produce blisters if it comes in contact with normal skin or mucous membrane. If spilled on skin, wipe off at once, using acetone, alcohol or tape remover. Then wash vigorously with warm soapy water and rinse well. If spilled on mucous membrane or in eyes, flush with water, remove the precipitated film, and flush with water for an additional 15 minutes. Patients vary in their sensitivity to cantharidin and in rare cases tingling, burning or extreme tenderness may develop. In these cases, patient should remove tape and soak the area in cool water for 10 to 15 minutes, repeating as required for relief. If soreness persists, puncture blister using sterile technique, apply antiseptic and cover with tape. It is advisable to treat only 1 or 2 lesions on the first visit, until the sensitivity of the patient is known.
Availability And Storage: Each mL contains: cantharidin 0.7% in an adherent film-forming vehicle. Bottles of 7.5 mL with thin-tipped applicator attached to inside of cap. Flammable. Keep away from heat, fire and flame. Close tightly immediately after use. Store at room temperature away from heat.
CANTHACUR® Pharmascience Cantharidin Vesicant