Levamisole in the adjuvant treatment of colon cancer

The chemistry, pharmacology, pharmacokinetics, assay methodologies, adverse effects, and dosage of levamisole are described, and the clinical studies of levamisole therapy in patients with colorectal carcinoma are reviewed. Levamisole is a synthetic, orally active agent that has antihelmintic and immunomodulatory properties. It is capable of inducing T-cell differentiation and restoring depressed effector functions of peripheral lymphocytes and phagocytes to normal. The drug is well absorbed from the gastrointestinal tract after oral administration and is extensively metabolized by the liver. Gas chromatography and high-performance liquid chromatography are the most common methods used to measure concentrations of levamisole in biologic fluids. Levamisole combined with fluorouracil has been associated with a one-third reduction in recurrence and risk of death in patients with surgically resected Dukes stage C colon cancer; this combination is now recommended as standard therapy in these patients. Uses in patients with rectal carcinoma, Dukes stage B colon cancer, metastatic colon cancer, other malignancies, or nonmalignant disorders remain investigational. Common adverse effects include nausea, abdominal pain, vomiting, diarrhea, metallic or altered taste, flulike symptoms, mood elevation, insomnia, hyperalertness, dizziness, and headache. The most serious adverse effect associated with levamisole is granulocytopenia. The FDA-approved dosage of levamisole is 50 mg orally every eight hours for three days every two weeks. Levamisole therapy is to be initiated no earlier than 7 and no later than 30 days after surgery and is to be continued for one year. Levamisole combined with fluorouracil has been associated with a one-third reduction in recurrence and risk of death in patients with resected stage C colon cancer. Further research is needed to more clearly define the mechanism of action, optimum dose and scheduling, and clinical efficacy of levamisole in treating other malignancies.