Stronghold For Dogs 20.1-40 lbs (10.1-20 kg)

Description

Stronghold for Dogs 20.1–40 lbs (10.1–20.0 kg) delivers 120 mg selamectin per 1.0 ml tube, manufactured by Zoetis as a topical spot-on solution for medium-sized dogs. Selamectin is a macrocyclic lactone avermectin that disrupts chloride channel conductance in invertebrate nerve and muscle cells, producing paralysis and death across a spectrum of internal and external parasites through systemic distribution following skin absorption. This variant is labeled for dogs from 6 weeks of age weighing between 10.1 and 20.0 kg, with monthly application covering flea prevention and heartworm larval prevention, and single-dose treatment for ear mites, roundworms, and biting lice, alongside a two-dose monthly protocol for sarcoptic mange.

Recommended for

Dogs weighing 20.1–40 lbs (10.1–20.0 kg) from 6 weeks of age.

Indication/Coverage

For dogs suffering from, or at risk from, mixed parasitic infections, Stronghold 120 mg addresses the following conditions:

• Flea treatment and prevention (Ctenocephalides spp.): Selamectin eliminates adult fleas on the dog, halts viable egg production, and destroys environmental larvae; ovicidal activity is sustained for 3 weeks post-application, interrupting the flea reproductive cycle across every stage present on the animal and in accessible surroundings.
• Heartworm prevention (Dirofilaria immitis, L3/L4 larvae): Each monthly dose eliminates susceptible larval stages acquired during the preceding 30-day interval; the product carries no activity against established adult heartworms already residing in the pulmonary vasculature.
• Ear mite treatment (Otodectes cynotis, adults): A single dose constitutes the full labeled treatment course; loose debris from the external ear canal should be gently cleared at the time of treatment, and a veterinary follow-up at 30 days is recommended as a proportion of dogs require a second application.
• Roundworm treatment (Toxocara canis, adults): A single dose eliminates adult intestinal roundworm burden from the gastrointestinal tract.
• Sarcoptic mange treatment (Sarcoptes scabiei): Complete mite eradication requires one dose on each of two consecutive months; administering both doses simultaneously does not satisfy the labeled protocol.
• Biting lice treatment (Trichodectes canis): A single topical application resolves biting lice infestations in dogs within this weight range.

Key Benefits

The following characteristics are confirmed by the Stronghold label for the 120 mg dose covering dogs in the 10.1–20.0 kg range.

• Dose precision for medium dogs: The 120 mg selamectin dose sustains a minimum of 6 mg/kg across the full 10.1–20.0 kg range, keeping the per-kilogram concentration within the labeled therapeutic window at both weight boundaries.
• Six-indication single application: One monthly tube addresses fleas, heartworm larvae, ear mites, roundworms, sarcoptic mange, and biting lice, consolidating external and internal parasite coverage into a single topical dose.
• Flea population suppression beyond the animal: Debris shed from a selamectin-treated dog kills flea eggs and larvae in the environment that have not been directly exposed to the compound, extending flea control into areas the dog frequents.
• Transdermal route for internal coverage: Selamectin is absorbed through the skin following neck application and reaches maximum plasma concentration within approximately 3 days in dogs, delivering heartworm larval and roundworm coverage without requiring the dog to accept an oral dose.
• Sustained 30-day activity: The terminal elimination half-life of selamectin in dogs is approximately 11 days, maintaining detectable plasma concentrations throughout the full monthly dosing interval and supporting consistent flea and heartworm larval protection.
• Post-bath efficacy retention: The Stronghold label confirms that bathing or immersion 2 or more hours after application does not reduce product efficacy, making this variant practical for medium-sized dogs that swim regularly or require frequent grooming.
• Pregnancy and lactation clearance: Zoetis administered Stronghold at 3 times the recommended dose to pregnant and lactating females without adverse effects, supporting its use in breeding females within this weight category.
• Established breed safety data: Zoetis safety data confirm no adverse effects at 10 times the recommended dose; field testing covered over 100 pure and mixed dog breeds, with ivermectin-sensitive collies tested separately at 5 times the recommended dose with no adverse effects observed.

Caution

Hazards to Humans

This product is highly flammable; keep it clear of heat sources, open flame, and sparks throughout handling. Do not smoke, eat, or drink during application. Wash hands thoroughly with soap and water immediately after use. Flush any skin or eye contact with water at once; seek medical attention if the eyes are exposed. Keep children away from treated dogs for at least 30 minutes or until the coat is fully dry.

Hazards to Domestic Animals

Stronghold 120 mg is for external use in dogs only; do not administer orally or by injection. This variant is not labeled for dogs under 6 weeks of age, and the dose covers animals up to 20.0 kg only. Do not apply when the coat is wet. Dogs that are debilitated or in poor condition for their age and size should not receive this product without prior veterinary assessment. Reversible neurological signs including seizures have been reported on rare occasions with macrocyclic lactone-class products; veterinary clearance is warranted before use in any dog with a known history of neurological sensitivity. No interactions with routinely used veterinary medications or surgical procedures were identified in extensive field trials.

Possible Side Effects

Monitor your dog after each application, with close attention following the first dose in the series.

Dermal reactions at the application site are uncommon. Temporary hair clumping or a small residue of white powder at the treated area within the first 24 hours is a documented characteristic of the drying solution; it resolves without any intervention and does not indicate a problem with safety or efficacy.

Systemic reactions are exceptional. As a macrocyclic lactone, selamectin carries a documented but very low risk of reversible neurological signs including seizures; this has occurred only rarely across extensive breed and safety testing. Ivermectin-sensitive collie breeds were included in safety studies at 5 times the recommended dose without adverse neurological findings, though individual sensitivity in any given animal cannot be entirely ruled out.

If persistent skin changes, behavioral shifts, or unexpected systemic signs emerge after dosing, discontinue use and consult a veterinarian without delay.