Imiquimod Cream for Venereal Warts
Imiquimod Cream for Venereal Warts
By William T. Elliott, MD, FACP, and James Chan, PharmD, PhD
The fda has approved a new topical agent for the treatment of genital warts. Imiquimod cream (Aldara, 3M Pharmaceuticals) is a topically applied immune response modifier. Its mechanism of action is believed to be induction of cytokines including interferon alpha.1
Genital warts are caused by strains of the sexually transmitted human papillomavirus (HPV). Nearly one million cases of genital HPV infection are diagnosed each year, with the highest incidence among sexually active teenagers. It is estimated that as many as one-quarter to one-third of all sexually active teenagers in this country have been exposed to HPV.2,3
Indications
Imiquimod is approved for the treatment of external genital and perianal warts/condyloma acuminata in adults.
Potential Advantages
Imiquimod offers topical therapy with a different mechanism of action than other available agents. Imiquimod is believed to induce interferon synthesis, while podofilox/podophyllin is an antimitotic agent. Compared to podofilox, fewer applications are required. Unlike podofilox, there is no limitation to the surface area of application. Imiquimod is a Pregnancy category B compared to category C for podofilox.
Potential Disadvantages
Imiquimod is less effective in males than females. In a phase III trial (n = 311), total lesion clearance rate was 72% for females, compared to 33% for males. Imiquimod also has a slow onset of action. The median time to total wart clearance ranges from eight weeks for females to 12 weeks for males.1 The median time for podofilox is 2.6 weeks.4 The recommended maximum duration of therapy is 16 weeks. The cream should be washed off after 6-10 hours. Local reactions such as erythema, erosion, itching, and burning are commonly reported side effects with incidences from 26% to 61%.1
Dosing Information
Aldara is supplied as imiquimod cream, 5% in single-use packets containing 250 mg. The cream is applied three times per week at bedtime and left on for 6-10 hours, then washed off with soap and water. The treatment should be continued until there is total clearance of genital or perianal warts or a maximum of 16 weeks. Hands should be washed after application.1
Comments
Genital and anal warts are benign growths caused by human papillomavirus. No therapy has been shown to eradicate the virus; thus, the goal of treatment is to remove the warts and improve symptoms. In placebo-controlled trials, warts have cleared spontaneously in 20-30% of patients within three months. Treatment success with various modalities is 22-94%, with a recurrence rate of 25% or greater in three months.5
Imiquimod is a new topical agent for external genital and perianal warts. It represents the second self-applied product after podofilox with a potentially different mode of action. There are no published comparative trials at this time between imiquimod and podofilox, although overall response rates appear similar. Relative side effects and recurrence rates cannot be reliably assessed. Imiquimod has a slower onset of action than podofilox, may be more effective in women, and is more expensive. The wholesale cost is about $90 per month. This is about twice the cost of podofilox solution or gel on a per-month basis. In addition, a longer treatment time is required to achieve clinical benefit.
Clinical Implications
Imiquimod cream is a useful alternative to other treatments for genital and perianal warts, particularly in women.
References
1. Aldara Product Monograph. 3M Pharmaceutical. March 1997.
2. Centers for Disease Control and Prevention. Annual Report; 1994.
3. Lowry DR, et al. Proc Natl Acad Sci USA. 1994;91:2436-2440.
4. Condylox Product Information. Oclasson Pharmaceutical, Inc.
5. MMWR Morb Mortal Wkly Rep 1993;42:83.
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