Stronghold Plus for Cats - Dosage and Side Effects

Laura García Ortiz
By Laura García Ortiz, Veterinarian specialized in feline medicine. September 28, 2023
Stronghold Plus for Cats - Dosage and Side Effects

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Stronghold plus for cats is a broad-spectrum antiparasitic agent which is used to combat both internal and external parasites. Unlike many other antiparasitic deworming agents for animals, Stronghold Plus has two active ingredients. This provides protection against external parasites such as fleas, ticks and mites, as well as internal parasites such as roundworm, heartworm and other nematodes. To ensure this protection is optimal, we need to apply Stronghold Plus with the correct dosage. Since it is such a strong antiparasitic, it is also important to ensure we are considerate of any side effects or reactions.

At AnimalWised, we explain everything you need to know about Stronghold Plus for cats. We explain its dosage and side effects, as well as how to apply Stronghold Plus to your cat for maximum protection against parasites.

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  1. What is Stronghold Plus for cats?
  2. What is Stronghold Plus for cats used for?
  3. How to apply Stronghold Plus for cats
  4. Stronghold Plus for cats side effects
  5. Stronghold Plus for cats contraindications

What is Stronghold Plus for cats?

Stronghold plus is an antiparasitic product that is composed of a combination of two macrocyclic lactones, selamectin and sarolaner:

  • Selamectin: this compound is a type of avermectin that is responsible for killing and/or paralyzing various parasitic invertebrates. It works by interfering with their chlorine channel conductibilities, in turn this results in normal neurotransmission being interrupted. This affects the electrical activity of the muscle cells of arthropods and the nerve cells of nematodes, resulting in paralysis. Since they cannot function, the parasites die.

  • Sarolaner: this active ingredient of Stronghold Plus for cats is an isoxazoline. Its action against parasites is the blocking of chloride channel function. These channels are linked to glutamate and GABA receptors in the nervous system of parasites. Sarolaner produces an increase in nervous stimulation, resulting in their death.

As we have stated already, this preventive drug works for both internal and external parasites. We discuss this further below, but you can also learn about the most common external parasites in cats with our related article.

What is Stronghold Plus for cats used for?

Stronghold Plus is a broad-spectrum antiparasitic product for feline species. This means it kills and protects against a wide range of parasites. This is contrasted against other anthelmintic and insecticidal drugs which only kill a certain species or type. For this reason, Stronghold Plus is effective against the following parasites:

  • Fleas: such as Ctenocephalides felis and Ctenocephalides canis with activity against eggs, larval forms and adults. This means it breaks the life cycle of the flea and can help eradicate infestations. In addition, skin flakes from the cat with Stronghold Plus kill the eggs and larvae of fleas in the environment upon contact. This activity begins 24 hours after application and lasts 5 weeks.

  • Mites: such as Otodectes cynotis.

  • Lice: such as Felicola subrostratus.

  • Intestinal nematodes: such as hookworms (e.g. Ancylostoma tubaeforme) and roundworms (Toxocara cati). Learn more about the different types of worms in cats.

  • Filaria larvae: such as Dirofilaria immitis. This is a parasite known as heartworm which can be potentially fatal and is also contorlled by other drugs such as Milbemax for cats.

  • Ticks: such as Ixodes ricinus, Ixodes hexagonus, Rhipicephalus sanguineus and Dermacentor reticulatus.
Stronghold Plus for Cats - Dosage and Side Effects - What is Stronghold Plus for cats used for?

How to apply Stronghold Plus for cats

There are various preparations of antiparasitic dewormers for cats, but Stronghold Plus comes as a pipette. This allows us to squeeze the liquid medication onto the skin of the cat. This is absorbed into the follicles to provide protection against external parasites, as well as entering the bloodstream for internal parasite protection.

Stronghold Plus pipettes are most effective when applied to the dorsal area of the neck between the shoulders. This is because the cat cannot reach this area for grooming, so the product has time to absorb and spread across their body. It is applied in a single application with the appropriate format according to the weight of the cat.

Stronghold Plus for cats dosage

  • Cats weighing less than 2.5 kg: a 0.25 ml pipette containing 15 mg of selamectin and 2.5 mg of sarolaner.
  • Cats weighing 2.5-5 kg: a 0.5 ml pipette containing 30 mg selamectin and 5 mg sarolaner is used.
  • Cats weighing between 5-10 kg: a 1 ml pipette containing 60 mg of selamectin and 10 mg of sarolaner.

To apply this Stronghold Plus pipette correctly, you will have to remove it from the packaging and separate the hair in the application area until the skin is visible. This is the area between the shoulder blades at the base of the neck. Once we have done this, we will have to apply the tip of the pipette until its entire contents are emptied into a single point.

Discover another type of deworming agent for felines with our article on ivermectin for cats.

Stronghold Plus for cats side effects

Within 24 hours of applying Stronghold plus, caking of the hair may occur. We may also see dry white or greasy deposits in the application area. Although it does not usually cause adverse effects, this medication may cause temporary itching at the application site that may be accompanied by mild to moderate alopecia and erythema.

In very rare occasions, cats may also drool or have neurological signs such as ataxia or epilepsy. Gastrointestinal signs such as diarrhea, anorexia or vomiting are likely if the product is ingested orally.

Learn more about the causes of diarrhea and vomiting in cats.

Stronghold Plus for Cats - Dosage and Side Effects - Stronghold Plus for cats side effects

Stronghold Plus for cats contraindications

As with all other veterinary medicines, Stronghold Plus has certain contraindications for use. They include the following:

  • Do not use in underweight or weak cats
  • Do not use in cats that are suffering from or being treated for any pathological process
  • Do not apply to cats with known allergy or hypersensitivity to the active ingredients or excipients
  • Do not use in pregnant or lactating cats

Although selamectin is considered safe for use in pregnant or lactating felines, its safety has not been proven for sarolaner.

Stronghold Plus is a great borad-spectrum deworming treatment for cats, but it is not effective against all types of parasite. For example, the literature does not provide information about its protection against giardia in cats.

This article is purely informative. AnimalWised does not have the authority to prescribe any veterinary treatment or create a diagnosis. We invite you to take your pet to the veterinarian if they are suffering from any condition or pain.

If you want to read similar articles to Stronghold Plus for Cats - Dosage and Side Effects, we recommend you visit our Medicine category.

  • European Medicines Agency. Stronghold Plus technical sheet. Retrieved from:
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Stronghold Plus for Cats - Dosage and Side Effects