Praziquantel is a narrow-spectrum antiparasitic active ingredient used in veterinary and human medicine. It is used in dogs, cats, horses and livestock against internal parasites, mainly tapeworms. It is not used against agricultural and household pests. It belongs to the chemical class of the isoquinolines.


Type: veterinary medecine
Chemical class: isoquinoline


Molecular structure of PRAZIQUANTEL 


Type of action: Anthelmintic taenicide, endoparasiticide.
Main veterinary parasites controlledtapeworms (=cestodes), pancreas fluke (Eurytrema pancreaticum), blood flukes (Schistosoma spp)

Efficacy against a specific parasite depends on the delivery form and on the dose administered.

Click here for general information on features and characteristics of PARASITICIDES.


Click here to view the article in this site with the most common dosing recommendations for praziquantel used in domestic animals.


Oral LD50, rat, acute*: >2840 mg/kg
Dermal LD50, rat, acute*: not found
* These values refer to the active ingredient. Toxicity has to be determined for each formulation as well. Formulations are usually significantly less toxic than the active ingredients.

MRL (maximum residue limit) established for either beef, mutton pork or chicken meat*:

  • CODEX: No
  • EU: No (Annex II, not needed)
  • USA: No
  • AUS: No

* This information is an indicator of the acceptance of an active ingredient by the most influential regulatory bodies for use on livestock.

Withholding periods for meat, milk, eggs, etc. depend on delivery form, dose and national regulations. Check the product label in your country.

Learn more about praziquantel safety (poisoning, intoxication, overdose, antidote, symptoms, etc.).

General safety information for antiparasitics is available in specific articles in this site (click to visit):


It is obvious that veterinary products are not intended for and should never be used on humans!!!


Decade of introduction: 1970
Introduced by: BAYER
Patent: Expired (particular formulations may be still patent-protected)

Use in LIVESTOCK: Yes, very scarce
Use in HORSES: Yes, abundant
Use in DOGS and CATS: Yes, a lot

Main delivery forms: 

Use in human medicine: Yes
Use in public/domestic hygiene: No
Use in agriculture: No
Generics available:  Yes, a lot


With praziquantel alone

With praziquantel + pyrantel

With praziquantel + other active ingredients


In pets: No
In livestock & horses: No

Learn more about parasite resistance and how it develops.


Praziquantel is an excellent taenicide belonging to the chemical class of the isoquinolines. It is very much used in dogs and cats in various delivery forms (e.g. suspensions, injectables, tablets, pills, etc.). It is very much less used in livestock (a few products for sheep) or birds.

Due to its narrow spectrum of activity it is often used on pets in combination with a broad spectrum nematicide (e.g. macrocyclic lactones, benzimidazoles, tetrahydropyrimidines, etc.)

Efficacy of praziquantel

Praziquantel is highly effective against adults of many parasitic tapeworms (i.e. cestodes, e.g. of the genus Dipylidium, Taenia, Echinococcus, Mesocestoides, Moniezia, Avitellina, Stilesia, etc.) as well as against a few flukes (i.e. trematodes, e.g. of the genus Eurytrema and Schistosoma). It is also effective against larvae and/or eggs of certain species. 

The delivery form can influence the efficacy against certain parasites: e.g. efficacy against Echinococcus is usually lower after subcutaneous injection than after oral administration.

It has no efficacy whatsoever against roundworms (nematodes) and other important parasitic flukes such as liver flukes (Fasciola spp) or stomach flukes (Paramphistomum spp), nor against external parasites.

Praziquantel has no residual effect. This means that a single administration will kill the parasites present in the host at the time of treatment, but will not protect the host against re-infestations.

Pharmacokinetics of praziquantel

After oral or parenteral (injection) administration praziquantel is quickly and almost completely absorbed into the bloodstream in all species. Maximum plasma levels are reached 30 to 120 minutes after administration in dogs, 2 hours after administration in sheep. It is also quickly distributed throughout the whole body: highest concentrations are found in the liver and the kidneys. It is partly released back to the gut lumen, which makes it effective against parasitic stages in the intestinal wall.

Praziquantel is quickly metabolized to ineffective metabolites. Half-life in plasma is about 30 minutes, i.e., the anthelmintic effect is rather brief and hence it's lack of residual effect.

Excretion is accomplished 40 to 70% through urine, the rest through bile and feces, almost completely in the form of its metabolites. Less than 1% is excreted unchanged. Excretion half-life in dogs and sheep is 2 to 3 hours. Twenty-four hours after treatment 80% of the administered dose has been excreted, 48 hours after treatment excretion is complete.

Mechanism of action of praziquantel

The molecular mode of action of praziquantel is not precisely known at present. In Schistosoma worms it seems to affect the permeability of the calcium ions in the muscular membrane. As consequence the worms are paralyzed and die. In tapeworms it seems to affect carbohydrate metabolism and to damage the worm's tegument structures. As a consequence the parasites cannot avoid being digested by the gastric fluids of the host.

Click here to view the list of all technical summaries of antiparasitic active ingredients in this site.