EVIDENCE-BASED ANSWER
Of the available oral therapies for common warts, none has sufficient evidence to recommend it as an effective therapy (strength of recommendation [SOR]: B). To date, no oral agent has been shown to be effective in a randomized, placebo-controlled, double-blinded trial. Very limited evidence is emerging that zinc may be effective (SOR: C).
CLINICAL COMMENTARY
Persistent treatment with topical/intralesional therapy should continue to be the mainstay
Christopher P. Paulson, MD
US Air Force Family Medicine Residency, Eglin Air Force Base, Eglin, Fla
Verruca vulgaris (the common wart) is frequently encountered by the family physician, often after unsuccessful topical treatment. Unfortunately, evidence is insufficient to warrant routine use of oral agents such as cimetidine, zinc, or levamisole in the treatment of refractory lesions. The added cost and potential side effects of proposed oral treatments isn’t justified until more rigorous studies show clear clinical efficacy. Persistent treatment with proven topical and intralesional therapy for refractory lesions should continue to be the mainstay of therapy for verruca vulgaris.
Evidence summary
Oral therapies for common warts suffer from a lack rigorous clinical data regarding their efficacy. A detailed literature search found multiple trials evaluating various oral agents. However, only 6 trials met the selection criteria of randomized, controlled trials published in English.
Cimetidine (Tagamet) has been compared with placebo in 3 trials1-3 and was not found superior to placebo. Levamisole (Ergamisol), used in combination with cimetidine, has been compared with cimetidine alone in 2 trials,4,5 and was found to be effective at speeding regression of warts, with patients in the combination arm showing a mean regression time of 7.8 weeks compared with 11 weeks in the cimetidine alone group. These small studies involved 48 and 44 patients, respectively. In addition, 1 nonrandomized controlled trial6 found levamisole at 5 mg/kg for 3 days every 2 weeks to be superior to placebo in achieving complete cure of warts in a group of 40 patients.
Zinc is the only agent to demonstrate efficacy in a completely randomized and placebo-controlled study.7 However, this trial was unblinded, had only 40 subjects assigned to each agent, had a dropout rate of 46%, and did not follow intention-to-treat analysis.
Recommendations from others
Clinical Evidence lists cimetidine and levamisole as therapies of unknown effectiveness.8 The commentary on both agents notes that the size of each randomized controlled trial cited may have been too small to detect clinically important differences.