A double-blind, controlled trial of
levamisole in the prevention and treatment of recurrent
cold sores was performed. Forty-eight subjects received
levamisole in a dosage of 2.5 mg/kg on two consecutive days each week for six months. The 51 control subjects were given a placebo identical to the
drug in appearance. Both groups were given the same instructions. Nineteen subjects receiving
levamisole and eight receiving placebo withdrew during the six months of the study. There were no significant differences between the
levamisole-treated and control groups in the duration or severity of the lesions during the trial period or in the subjective assessment of
drug efficacy by the participants at the end of the trial. Before treatment the frequency of lesions in the
levamisole group was higher than in the control group. Only when this factor was taken into account by analysis of covariance did the decreased frequency of lesions during
therapy appear significantly lower in the group receiving
levamisole than in the placebo group. The difference remained clinically unimpressive. This study does not support earlier suggestions that
levamisole, in these doses, is useful in the treatment of recrudescent circumoral
herpesvirus infections.