Interferon for Condyloma: Intralesional Administration Only
Interferon therapy for condyloma acuminata (genital warts) should be administered intralesionally (injected directly into the warts), not subcutaneously at distant sites, as systemic subcutaneous interferon is not effective for this indication. 1
Route of Administration
The CDC guidelines explicitly state that interferons for genital warts have been administered in two ways: systemically (subcutaneously at a distant site or intramuscularly) and intralesionally (injected into the warts). Systemic interferon is not effective, while intralesional interferon has efficacy and recurrence rates comparable to other treatment modalities. 1
Specific Interferon Products Used Intralesionally
Interferon alfa-2b (recombinant): Injected directly into warts at 1 × 10⁶ IU per wart, three times weekly for three weeks, producing 62% reduction in wart area and 36% complete clearance at 13 weeks post-treatment. 2
Natural interferon alfa (Alferon N): Injected intralesionally twice weekly for up to eight weeks, achieving complete wart elimination in 62% of patients compared to 21% with placebo. 3
Interferon alfa-2 (recombinant): Administered at 10⁶ IU per wart three times weekly for three weeks, resulting in 53% complete clearing of treated condyloma. 4
Why Subcutaneous Interferon Fails for Condyloma
Research directly comparing systemic versus intralesional administration demonstrates that subcutaneous interferon alpha-2b given at distant sites (either 3 MU/m² daily IM for 3 weeks or 3 MU/m² subcutaneously three times weekly for 4 weeks) achieved only 20% complete response rates at 6 months, comparable to the 8% spontaneous resolution in untreated controls. 5 A separate trial using 1.5 MIU subcutaneous interferon alpha-2a three times weekly for 4 weeks showed no difference in efficacy compared to placebo at 3 months. 6
Current Clinical Recommendation
Interferon therapy is not recommended for routine use in condyloma treatment due to inconvenient routes of administration (requiring intralesional injection into each wart), frequent office visits, and high frequency of systemic adverse effects including flu-like symptoms, fatigue, fever, chills, myalgia, headache, and leukopenia. 1
Preferred Alternative Treatments
The CDC recommends patient-applied therapies (podofilox 0.5% solution or imiquimod 5% cream) or provider-administered treatments (cryotherapy with liquid nitrogen, TCA/BCA 80-90%, or surgical removal) as first-line options, reserving intralesional interferon only for refractory cases. 7, 8