Medically Reviewed on 4/7/2022

Generic Name: praziquantel

Brand Name: Biltricide

Drug Class: Anthelmintics

What is praziquantel, and what is it used for?

Praziquantel belongs to a class of medications known as anthelmintics used to treat diseases caused by certain parasitic worm infestations, including schistosomiasis, clonorchiasis and opisthorchiasis. Schistosomiasis is a disease caused by a type of worm that lives in the blood vessels (blood flukes) and clonorchiasis and opisthorchiasis are caused by liver flukes that live in bile ducts. 

The Schistosoma species of parasites live in certain kinds of freshwater snails found in Africa, South America, Caribbean, Middle East and parts of Asia. When their eggs hatch, the larvae emerge into the water, and enter people’s bodies through the skin when they come into contact with the contaminated water. The larvae get into the bloodstream, develop into adults and lay eggs, some of which are passed in the urine and stools. The eggs that get lodged in tissues cause infection, inflammation and eventually, organ damage.

Liver fluke infection occurs from eating fluke-infested fresh water raw or undercooked fish, crabs or crayfish found in certain parts of Asia and Europe. Liver flukes pass through the intestinal walls and settle in the bile ducts. Mature adults may live up to 20-30 years, and untreated infections can persist and cause lasting damage. While a majority of people remain asymptomatic, in some people, the parasite can cause chronic liver inflammation that can even lead to liver cancer.

Praziquantel kills the flukes by making structural changes, severely paralyzing the worm’s muscles and increasing the permeability of their cell membranes to calcium. The paralysis and calcium influx into their cells dislodge the worms from the blood vessel/bile duct and kill them.

Praziquantel is approved to treat:

  • Schistosomiasis caused by all species of Schistosoma
  • Clonorchiasis cause by Clonorchis sinensis
  • Opisthorchiasis caused by Opisthorchis viverrini

Off-label uses include:

  • Intestinal tapeworm infections
  • Cysticercosis caused by Taenia solium which can affect brain, muscle or other tissue


  • Do not use praziquantel in the following circumstances:
    • Hypersensitivity to praziquantel or any of its components
    • Cysticercosis in the eye
    • Simultaneously with medications that are CYP450 inducers such as rifampin, which increase the activity of the enzyme CYP450 which metabolizes drugs; it may cause rapid metabolization of praziquantel and reduce its bioavailability 
  • Clinical deterioration may occur while treating schistosomiasis, due to inflammatory response to substances released by the dying parasites; monitor carefully
  • Use with caution in people with central nervous system disorders such as epilepsy; may aggravate the condition
  • It is advisable to hospitalize the patient for the duration of treatment, when schistosomiasis or fluke infection is found to be associated with cerebral cysticercosis
  • Patients with cardiac irregularities should be monitored during treatment
  • Minimal increases in liver enzymes have been reported in some patients
  • Use with caution in people with impaired liver function; reduced metabolization of praziquantel may lead to high blood concentrations of unmetabolized drug


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What are the side effects of praziquantel?

Common side effects of praziquantel include:

Less common side effects of praziquantel include:

Rare side effects of praziquantel include:

  • High eosinophil count in blood (eosinophilia)
  • Bloody diarrhea
  • Allergic reaction (generalized hypersensitivity, including inflammation of the serous membranes that cover the inner organs [polyserositis])
  • Irregular heart rhythms (arrhythmia) including:
    • Slow heartbeat (bradycardia)
    • Premature atrial contraction (ectopic rhythms)
    • Ventricular fibrillation
    • Interruption of impulse transmission between heart chambers (atrioventricular blocks)
  • Fatigue
  • Weakness (asthenia)
  • Vertigo
  • Convulsions
  • Muscle pain (myalgia)

This is not a complete list of all side effects or adverse reactions that may occur from the use of this drug.

Call your doctor for medical advice about serious side effects or adverse reactions. You may also report side effects or health problems to the FDA at 1-800-FDA-1088.

What are the dosages of praziquantel?


  • 600mg



  • 20 mg/kg orally three times a day for 1 day (at intervals of 4-6 hours)  

Clonorchiasis, Opisthorchiasis

  • 25 mg/kg orally three times a day for 1 day (at intervals of 4-6 hours)

Cysticercosis (Off-label)

  • 50-100 mg/kg/day orally divided every 8 hour for 14 days  

Tapeworms (Off-label)

  • 5-10 mg/kg as single dose or 25 mg/kg if caused by Hymenolepis nana



  • Children younger than 4 years: Safety and efficacy not established
  • Children 4 years and older: 20 mg/kg orally three times a day for 1 day (at intervals of 4-6 hours)

Clonorchiasis, Opisthorchiasis

  • Children younger than 4 years: Safety and efficacy not established
  • Children 4 years and older: 25 mg/kg orally three times a day for 1 day (at intervals of 4-6 hours)  

Cysticercosis (Off-label)

  • Children younger than 4 years: Safety and efficacy not established
  • Children 4 years and older: 50-100 mg/kg/day orally divided three times a day for 30 days  

Tapeworms (Off-label)

  • Children younger than 4 years: Safety and efficacy not established
  • Children 4 years and older: 5-10 mg/kg as single dose or 25 mg/kg if caused by Hymenolepis nana


  • There is no data available on the overdose of praziquantel. In case of overdose, a fast-acting laxative should be administered.

What drugs interact with praziquantel?

Inform your doctor of all medications you are currently taking, who can advise you on any possible drug interactions. Never begin taking, suddenly discontinue, or change the dosage of any medication without your doctor’s recommendation.

The drug interactions listed above are not all of the possible interactions or adverse effects. For more information on drug interactions, visit the RxList Drug Interaction Checker.

It is important to always tell your doctor, pharmacist, or health care provider of all prescription and over-the-counter medications you use, as well as the dosage for each, and keep a list of the information.

Check with your doctor or health care provider if you have any questions about the medication.

Pregnancy and breastfeeding

  • Animal studies do not reveal any evidence of fertility impairment or fetal harm with use of praziquantel during pregnancy. There are no well-controlled studies of praziquantel use in pregnant women; use with caution.
  • Praziquantel is present in breast milk at low concentrations, however, its effects on the breastfed infant is not known. Women should not nurse on the day of praziquantel treatment and during the subsequent 72 hours.

What else should I know about praziquantel?

  • Although Schistosoma and most of the other worms are not found in the U.S., they are found in many countries globally; exercise caution while traveling
  • Avoid hazardous tasks such as driving or operating heavy machinery on the day of treatment with praziquantel, and the following day

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Praziquantel is an anthelmintic medication used to treat diseases caused by parasitic worm infestations, including schistosomiasis, clonorchiasis, and opisthorchiasis. Common side effects of praziquantel include feeling unwell (malaise), headache, dizziness, excessive sweating (diaphoresis), abdominal discomfort and pain, nausea, vomiting, fever, drowsiness (somnolence), appetite loss (anorexia), and cerebrospinal fluid (CSF) reaction syndrome in patients treated for neurocysticercosis. Consult your doctor if pregnant or breastfeeding.

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You are encouraged to report negative side effects of prescription drugs to the FDA. Visit the FDA MedWatch website or call 1-800-FDA-1088.

Medically Reviewed on 4/7/2022