Levamisole: lack of immunopotentiation in a controlled trial

The immunopotentiating effect of levamisole was assessed in a double-blind trial in two comparable groups of patients with Down's syndrome, with which the immunodeficiency and susceptibility to infection are known to be associated. One group was given levamisole continuously and at the same dose for 16 weeks, and the other group was given placebo tablets. A checklist was designed to record the type, frequency, and duration of all infections which occurred in the patients, and delayed type hypersensitivity responses to various antigens were measured. There were no differences between the two groups in body weight, number of intercurrent infections, duration of illness, nor was there any change in degree of depression or cutaneous delayed-type hypersensitivity. These findings, taken with claims of success in some patients and failure in others, suggest that levamisole is not a general immunopotentiating agent, although it may have a specific site (or sites) of action on the immune system. If levamisole is to be used more selectively, this action needs to be characterized.