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Imiquimod is an immune response modifier. Studies have shown that it has potent immunomodulatory effects and stimulates human peripheral mononuclear cells to release interferon alpha, sub-types α1,α2, α5, α6, and α8. It also induces monocytes and macrophages to produce other cytokines including interleukins 1, 6, 8 and tumor necrosis factor α.2 The clinical relevance of these findings is not fully understood.
Previously available treatments (e.g. cryotherapy, laser vaporization, electrocautery and excision) for anogenital warts are often painful and expensive. Local therapy with podophyllin, or podophyllotoxin or trichloracetic acids, requires multiple applications, is slow acting and often causes problems associated with local inflammation.1 5-Fluorouracil, although sometimes used for external anogenital warts, is not yet approved for this indication, has neither antiviral nor immunomodulatory effects, earlier formulations were irritating and intralesional injections are painful.3,4 Unfortunately, recurrence often follows cessation of treatment following the use of these therapies.1
In early multicenter, double-blind, dose-ranging, vehicle controlled clinical trials, imiquimod 5% has proven effective in treating anogenital warts. In 311 patients, imiquimod 5% three times weekly completely cleared warts in 50% of patients, compared to 11% clearance in patients treated with the vehicle (p < 0.0001, intent-to-treat analysis). In a subsequent trial, daily application of the 5% cream completely cleared the warts of 52% of patients compared to 3% clearance of warts in patients using the vehicle alone (p < 0.0001, intent-totreat analysis). In these two trials, following cessation of treatment, wart recurrence rates were 13% and 19% respectively.7
The trials discussed above revealed that erythema and increased skin irritation was the most common reaction and was severe in 4% of both male and female patients treated three times weekly.9 Other adverse events reported by more than 1% of patients include fatigue, fever, influenza like symptoms, headache, diarrhea, myalgia and fungal infections.9
Safety During Pregnancy & Lactation
There are no adequate and well controlled studies in pregnancy and it is not known whether topically applied imiquimod is excreted in breast milk.
Percutaneous absorption was minimal (less than 0.9%) following a single dose, topical application of 5 mg of imiquimod to the skin of six healthy volunteers.
Dosage and Administration of Imiquimod
Prior to retiring, a thin layer of the cream is applied to the wart area, rubbed in until cream is no longer visible, left on the skin overnight and then in the morning washed off with mild soap and water. Hands should be washed before and after being used to apply the cream. The anogenital warts should be treated three times per week. For those patients who respond, clearance of warts requires on average 8 weeks for female patients and 12 weeks for male patients.
Imiquimod has not yet been compared to any other treatment for anogenital warts. Podophyllin, the most frequently used topical treatment, is not a standardised preparation10, has an unknown shelf life10, contains potentially carcinogenic mutagens and has no known antiviral/immunomodulatory activity. Imiquimod has no mutagenic activity, is immunomodulatory/antiviral and would appear to be the drug of choice3 for multiple warts when cryotherapy is inappropriate and cost is not a problem.
Preliminary clinical data suggests that this new treatment approach utilizing imiquimod to treat external genital and perianal warts/condyloma can be justified on phamacoeconomic grounds.
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Last modified: Thursday, 19-Feb-2015 17:10:23 MST