1. Clinical Overview
Praziquantel is a broad-spectrum anthelmintic agent, specifically a pyrazinoisoquinoline derivative, used primarily for the treatment of schistosomiasis (bilharzia) and infections caused by liver flukes (clonorchiasis, opisthorchiasis) and intestinal flukes (fasciolopsiasis). It is considered the drug of choice for most trematode and cestode infections. In the Indian context, it is a critical drug for public health programs targeting parasitic worm infections, particularly in endemic rural and peri-urban areas.
| Onset | Duration | Bioavailability |
|---|---|---|
| Rapid, with parasite paralysis occurring within 1-2 hours of administration. | The therapeutic effect is sustained post a single or short-course dose, with elimination of the parasite. The drug itself has a short plasma half-life. | Approximately 80% when administered orally, but undergoes significant first-pass metabolism, reducing systemic bioavailability to a variable extent. Absorption is increased up to 5-fold when taken with a high-fat meal. |
2. Mechanism of Action
Praziquantel increases the permeability of the cell membrane of susceptible worms to calcium ions, leading to massive contraction and paralysis of the parasite's musculature. This results in detachment from host tissues (e.g., blood vessel walls). The paralyzed worms are then dislodged and transported to the liver, where they are ultimately destroyed by the host's immune system. The drug also causes tegumental damage, exposing hidden antigens to the host's antibodies.
3. Indications & Uses
- Schistosomiasis (all species: S. haematobium, S. mansoni, S. japonicum)
- Clonorchiasis (Chinese liver fluke)
- Opisthorchiasis (Southeast Asian liver fluke)
- Intestinal fluke infections (e.g., Fasciolopsis buski)
4. Dosage & Administration
Adult Dosage: Schistosomiasis/Trematodes: 40-60 mg/kg as a single dose or 20 mg/kg three times in one day (depending on species). Intestinal tapeworms: 10-25 mg/kg as a single dose. Neurocysticercosis: 50 mg/kg/day in 3 divided doses for 14-30 days, with concomitant corticosteroids.
Administration: Tablet to be swallowed whole with water during a meal. Do not chew (bitter taste). For single-dose regimens, take with an evening meal. For multi-dose regimens, space doses 4-6 hours apart. A high-fat meal significantly enhances absorption.
5. Side Effects
Common side effects may include:
- Abdominal pain or discomfort
- Nausea
- Headache
- Dizziness
- Malaise
- Mild fever
- Pruritus
6. Drug Interactions
| Drug | Effect | Severity |
|---|---|---|
| Rifampicin | Markedly decreases praziquantel plasma levels by inducing CYP3A4, leading to therapeutic failure. | Major |
| Phenytoin / Carbamazepine | Decreases praziquantel plasma levels via CYP450 induction. | Major |
| Cimetidine | Increases praziquantel plasma levels by inhibiting CYP3A4, potentially increasing toxicity. | Moderate |
| Dexamethasone | May decrease praziquantel plasma levels (CYP3A4 induction). | Moderate |
| Chloroquine | May reduce bioavailability of praziquantel; administer at least 4 hours apart. | Moderate |
| Grapefruit juice | May increase praziquantel levels by inhibiting CYP3A4. | Minor |
7. Patient Counselling
- DO take the tablet whole with water during or immediately after a meal, preferably containing some fat.
- DO complete the full course as prescribed, even if you feel better.
- DO inform your doctor if you are taking any other medicines, especially for seizures or TB.
- DON'T chew or crush the tablet; it has a very bitter taste.
- DON'T drive or operate heavy machinery for 24 hours after taking the dose.
- DON'T take a second dose if you vomit within 1 hour of taking the tablet; consult your doctor.
8. Toxicology & Storage
Overdose: Nausea, vomiting, abdominal pain, drowsiness, dizziness, sweating, headache. In severe cases, ataxia, convulsions, and cardiac arrhythmias may occur.
Storage: Store below 30°C. Protect from light and moisture. Keep out of reach of children. Do not use after the expiry date printed on the pack.