Double-blind study of levamisole in aphthous stomatitis.

Sixty-five patients with recurrent aphthous stomatitis participated in a double-blind study to evaluate levamisole. Nineteen of 34 patients improved on levamisole and only five of 31 patients improved on placebo (P less than 0.004, chi-square with two degrees of freedom). After breaking the code and switching placebo patients to levamisole and non-responders to an alternate dosage schedule, 46 of 60 patients noted clinical improvement.