Levamisole is a synthetic imidazothiazole derivative with immunomodulatory and anthelmintic properties. In the Indian context, it is primarily used as an adjuvant therapy in colorectal cancer and for the treatment of ascariasis (roundworm infection) and hookworm infections. It acts by stimulating the immune system, particularly T-cell function and macrophage activation, and by causing paralysis in susceptible helminths.
Adult: **Anthelmintic:** 150 mg as a single dose (for ascariasis). For hookworm: 150 mg once daily for 3 days. **Adjuvant Cancer Therapy:** 50 mg every 8 hours (150 mg/day) for 3 days, repeated every 2 weeks, in combination with fluorouracil. The 150mg tablet is often used as a single daily dose in such regimens.
Note: Administer orally, with or without food. Tablet should be swallowed whole with a glass of water. For anthelmintic use, no special dietary restrictions or purging is necessary. In cancer therapy, dosing is precisely timed with fluorouracil administration.
Levamisole exhibits a dual mechanism. 1) As an anthelmintic, it acts as a nicotinic acetylcholine receptor agonist at the neuromuscular junction of susceptible nematodes, causing sustained depolarization, spastic paralysis, and subsequent expulsion of the worm by peristalsis. 2) As an immunomodulator, it restores depressed immune function in T-cells, monocytes, and macrophages. It enhances chemotaxis, phagocytosis, and intracellular killing by neutrophils and macrophages. It may also stimulate antibody formation and potentiate delayed-type hypersensitivity reactions.
Pregnancy: **Category C (US FDA). Contraindicated.** Animal studies have shown teratogenicity. There are no adequate and well-controlled studies in pregnant women. Risk of fetal harm outweighs any potential benefit. Effective contraception is advised during treatment.
Driving: May cause dizziness, vertigo, or blurred vision. Patients should be cautioned about operating machinery or driving until they are certain levamisole does not affect them adversely.
| Fluorouracil (5-FU) | Synergistic antitumor and toxic effects (myelosuppression, GI toxicity). Used therapeutically together but requires close monitoring. | Major |
| Phenytoin | Levamisole may inhibit metabolism of phenytoin, increasing its plasma levels and risk of toxicity. | Moderate |
| Warfarin | Levamisole may potentiate anticoagulant effect, increasing INR and bleeding risk. | Moderate |
| Alcohol | May cause a disulfiram-like reaction (flushing, tachycardia, nausea, vomiting). | Moderate |
| Other myelosuppressive drugs (e.g., Clozapine, Chemotherapy) | Increased risk of severe bone marrow suppression, especially agranulocytosis. | Major |