1. Clinical Overview
A fixed-dose combination of an anthelmintic (Diethylcarbamazine) and a first-generation antihistamine (Chlorpheniramine Maleate). Primarily used for the treatment and prophylaxis of lymphatic filariasis (caused by Wuchereria bancrofti and Brugia malayi) and tropical pulmonary eosinophilia. The combination is particularly effective in the Indian context for mass drug administration (MDA) programs and individual treatment. Chlorpheniramine helps mitigate the acute inflammatory reactions (Mazzotti-type reactions) commonly seen with Diethylcarbamazine therapy.
| Onset | Duration | Bioavailability |
|---|---|---|
| Diethylcarbamazine: Parasite death begins within 1-2 hours. Chlorpheniramine: 30-60 minutes. | Diethylcarbamazine: 6-12 hours. Chlorpheniramine: 4-8 hours. | Diethylcarbamazine: >85% (well absorbed). Chlorpheniramine Maleate: ~25-50% (subject to significant first-pass metabolism). |
2. Mechanism of Action
Diethylcarbamazine (DEC) immobilizes microfilariae by altering their surface membranes, making them susceptible to host phagocytosis by the reticuloendothelial system. It also damages adult worms, impairing their muscular activity and metabolism. Chlorpheniramine Maleate is a competitive reversible H1-receptor antagonist. It blocks the effects of histamine released during the inflammatory response to dying parasites, thereby reducing symptoms like itching, rash, fever, and malaise.
3. Indications & Uses
- Treatment of Lymphatic Filariasis (Bancroftian and Brugian)
- Prophylaxis of Lymphatic Filariasis in endemic areas
- Treatment of Tropical Pulmonary Eosinophilia (TPE)
4. Dosage & Administration
Adult Dosage: For Filariasis: 150mg DEC + 2.5mg Chlorpheniramine as a single dose. Often repeated annually in MDA. For TPE: 150mg DEC + 2.5mg Chlorpheniramine three times daily for 14-21 days.
Administration: Administer after meals to minimize GI upset. Tablet should be swallowed whole with a full glass of water. For MDA programs, administration is directly observed.
5. Side Effects
Common side effects may include:
- Drowsiness, sedation (Chlorpheniramine)
- Dizziness, headache
- Nausea, vomiting, anorexia
- Weakness, malaise
6. Drug Interactions
| Drug | Effect | Severity |
|---|---|---|
| Alcohol and other CNS Depressants (Benzodiazepines, Opioids) | Additive CNS depression and impaired psychomotor performance. | Major |
| Monoamine Oxidase Inhibitors (MAOIs) e.g., Phenelzine | Increased anticholinergic and CNS effects of Chlorpheniramine; risk of hypertensive crisis. | Contraindicated |
| Other Anticholinergics (Atropine, Tricyclic Antidepressants) | Enhanced anticholinergic side effects (dry mouth, urinary retention, confusion). | Major |
| Hepatic Enzyme Inducers (Phenobarbital, Rifampicin) | May reduce plasma levels of both components. | Moderate |
| Hepatic Enzyme Inhibitors (Cimetidine, Ketoconazole) | May increase plasma levels of both components, increasing toxicity risk. | Moderate |
7. Patient Counselling
- DO take the tablet after food.
- DO inform your doctor if you are pregnant, planning pregnancy, or breastfeeding.
- DO complete the full course as prescribed, even if symptoms improve.
- DO NOT consume alcohol while on this medication.
- DO NOT drive or operate machinery as it causes drowsiness.
- DO NOT take any other sedative or allergy medication without consulting your doctor.
8. Toxicology & Storage
Overdose: DEC: Nausea, vomiting, dizziness, headache, encephalopathy (in high doses with heavy infection). Chlorpheniramine: CNS depression (drowsiness, coma) or stimulation (insomnia, hallucinations), anticholinergic crisis (flushed skin, hyperthermia, tachycardia, seizures), cardiovascular collapse.
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.