Morantel is an antiparasitic active ingredient used in veterinary medicine. It is used in horses and livestock against internal parasites (mainly roundworms). It is not used against agricultural and household pests. It belongs to the chemical class of the tetrahydropyrimidines.

Common name:  MORANTEL

Type: veterinary medecine
Chemical class: tetrahydropyrimidine


Molecular structure of MORANTEL 


Type of action: Anthelmintic nematicide, endoparasiticide.
Main veterinary parasites controlled: Gastrointestinal roundworms = nematodes

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.


Morantel is a narrow-spectrum anthelmintic effective against gastrointestinal roundworms but not against those in the lungs or elsewhere in the host's body. It is also effective against certain tapeworms as well. It is ineffective against flukes (e.g. Fasciola hepatica). It is completely ineffective against external parasites.

Oral administration in the form of morantel tartrate is the rule. Nowadays it is used very scarcely in a few horse products (pastes & gels) but usage in livestock or pets is irrelevant.

Morantel has almost no residual effect, i.e. it kills the parasites during a few hours after treatment but offers no significant protection against re-infestation.

The table below indicates some usual dosing recommendations for morantel issued by manufacturers or documented in the scientific literature. They may not be approved in some countries.

Dosing recommendations for MORANTEL
Delivery Parasites Dose (against morantel-susceptible parasites)
Oral (tartrate) Gastrointestinal roundworms 7-15 mg/kg
Oral (tartrate) Gastrointestinal roundworms 6-12 mg/kg
Oral (tartrate) Gastrointestinal roundworms 7.5-12.5 mg/kg
Oral (tartrate) Tapeworms 7.5-12.5 mg/kg

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Dosing recommendations for antiparasitics depend on national regulations. National regulatory authorities determine whether a product is approved for a given indication, i.e. use on a particular host at a specific dose and against a specific parasite. Check the labels of the products available in your country for specific information on approved indications.


Oral LD50, rat, acute*: 551-586 mg/kg (tartrate); 986 mg/kg (tartrate, other source)
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: Yes
  • USA: Yes
  • AUS: Yes

* Any of the usual salts. 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 morantel 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: PFIZER → ZOETIS
Some original brands: PARATECT, RUMATEL, NEMATEL
Patent: Expired (particular formulations may be still patent-protected)

Use in LIVESTOCK: Yes, very low
Use in HORSES: Yes, rather scarce
Use in DOGS and CATS: No

Main delivery forms: 

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


In livestock: Yes, reported in the 1980s for Haemonchus sppOstertagia spp and Trichostrongylus spp  worms in sheep and goats, for Haemonchus spp in cattle, probably cross-resistance with levamisole. Nowadays morantel is very scarcely used in livestock.

Visit also the section in this site about parasite resistance to antiparasitics and more specifically to tetrahydropirimidines.


Morantel is a veteran, narrow-spectrum nematicide closely related to pyrantel and oxantel, all belonging to the tetrahydropyrimidines. It is mostly used as the tartrate salt.

Nowadays it is available in the form of feed additivestablets, or slow-release boluses for cattle, sheep and goats. However its use in livestock is moderate to low, because it has been replaced by other modern broad-spectrum anthelmintics.

It is not used in pets.

Efficacy of morantel

Morantel is highly effective against various adult gastrointestinal roundworms (e.g. of the genus Cooperia, Haemonchus, Nematodirus, Ostertagia, Trichostrongylus ). However, efficacy against immature stages is only ensured if present in the intestinal lumen. Stages in the tissues as e.g. arrested larvae are not controlled.

Unless delivered using a slow-release device, morantel has no residual effect. This means that a single administration will kill the parasites present in the host at the time of treatment, but it will not protect the host against re-infestations.

Morantel has no efficacy whatsoever against other non-gastrointestinal roundworms (pulmonary, skin, eyes, etc.), flukes (i.e. trematodes), and tapeworms (i.e. cestodes).

Pharmacokinetics of morantel

After oral administration morantel is very poorly absorbed to the bloodstream. It is excreted mainly in the feces in the form of the unchanged parent compound.

Mechanism of action of morantel

Tetrahydropyrimidines, including morantel, act on the nervous system of the worms as inhibitors of acetylcholinesterase (also known as AchE), an enzyme that hydrolyzes acetylcholine (Ach). Ach is a molecule involved in the transmission of nervous signals from nerves to muscles (so-called neuromuscular junctions) and between neurons in the brain (so-called cholinergic brain synapses). AchE's role is to terminate the transmission of nervous signals where acetylcholine is the neurotransmitter (there are several other neurotransmitters). Inhibition of AchE massively disturbs the normal movements of the parasites.

The bottom line for the parasitic worms is that they are paralyzed and die more or less quickly, or are expelled from the gut because they cannot keep themselves attached to the intestinal wall.

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