1. Clinical Overview
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.
| Onset | Duration | Bioavailability |
|---|---|---|
| Anthelmintic effect: Within hours. Immunomodulatory effect: Days to weeks. | Anthelmintic effect: Up to 24 hours. Immunomodulatory effect: Several weeks. | Approximately 80-90% after oral administration. |
2. Mechanism of Action
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.
3. Indications & Uses
- Adjuvant therapy in combination with fluorouracil (5-FU) for Duke's stage C colon cancer after surgical resection
- Treatment of ascariasis (roundworm infection caused by *Ascaris lumbricoides*)
4. Dosage & Administration
Adult Dosage: **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.
Administration: 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.
5. Side Effects
Common side effects may include:
- Nausea, vomiting, abdominal pain
- Diarrhea or loose stools
- Metallic taste
- Flu-like symptoms (fever, fatigue, myalgia, arthralgia) - often with immunomodulatory use
- Dizziness, headache
6. Drug Interactions
| Drug | Effect | Severity |
|---|---|---|
| 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 |
7. Patient Counselling
- **DO** take the tablet exactly as prescribed by your doctor.
- **DO** inform your doctor about all other medicines, vitamins, or herbal products you are taking.
- **DO** report any signs of infection (fever, sore throat), unusual bruising/bleeding, or skin rash immediately.
- **DO NOT** consume alcohol during treatment and for at least 48 hours after the last dose.
- **DO NOT** take this medicine if you are pregnant, planning pregnancy, or breastfeeding.
8. Toxicology & Storage
Overdose: Symptoms are extensions of side effects: **Severe nausea, vomiting, abdominal cramps, diarrhea, dizziness, headache, confusion, hallucinations, seizures, hypotension, and respiratory depression. Agranulocytosis risk is heightened.**
Storage: Store below 30°C, in a cool, dry place, protected from light and moisture. Keep out of reach of children. Do not use after the expiry date printed on the pack.