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Stronghold 120mg is a topical spot-on treatment specifically formulated for medium-sized dogs weighing 10.1kg to 20kg (22–44 lbs) — treating fleas, mites, and worm parasites, and preventing fleas and heartworm. Applied to the skin only; not designed for oral or injectable use.
Important: Stronghold treats adult roundworms (Toxocara canis) and prevents heartworm (Dirofilaria immitis) — it doesn’t treat an existing heartworm infection.
This item requires a current prescription from your vet before we can dispatch it. The good news? Sorting it out is simple and only takes a moment.
As soon as your prescription reaches us, our team will verify the details and get your pet’s treatment posted out to you.
Stronghold 120mg is a topical spot-on treatment specifically formulated for medium-sized dogs weighing 10.1kg to 20kg (22–44 lbs) — treating fleas, mites, and worm parasites, and preventing fleas and heartworm. Applied to the skin only; not designed for oral or injectable use.
Important: Stronghold treats adult roundworms (Toxocara canis) and prevents heartworm (Dirofilaria immitis) — it doesn’t treat an existing heartworm infection.
Supplied exclusively on prescription. Issued only after veterinary verification and approval.
Stronghold 120mg Spot-On Solution, prescribed for medium dogs (10.1–20kg)Stronghold 120mg is a prescription-only, colourless-to-yellow spot-on solution specifically formulated for medium dogs weighing between 10.1kg and 20kg. Applied directly to the skin at the back of the neck, this medication requires a monthly application to provide ongoing, continuous protection against fleas and heartworm.
For the treatment of roundworms, biting lice, and ear mites, a single dose is typically sufficient to clear the infestation. However, a veterinary re-check is highly recommended approximately 30 days after treating ear mites, as some dogs may need a second application.
Importantly, when treating sarcoptic mange, owners must administer a single dose for two consecutive months to ensure full clearance of the mites — making it the only condition listed that strictly requires a follow-up dose to prevent under-treating the infection.
From the datasheet, for dogs specifically, Stronghold does not treat ticks, tapeworms, or hookworms — and it prevents heartworm rather than treating an existing infection. If your dog already has heartworm, speak to your vet before starting treatment.
Worth Knowing: This particular strength (Stronghold 120mg) is built for one specific weight band: dogs between 10.1kg and 20kg — think Cocker Spaniel, Springer Spaniel, or a smaller Border Collie. You’ll know you’ve got the right pipette because the cap is red and it delivers exactly 1.0ml, containing 120mg of selamectin (a 12% concentration). Get a smaller or bigger dog onto this dose, and you’re either under-protecting them or giving more than they need, so the weight band strictly matters here — not just a label on the box.
Each 1.0ml pipette contains:
Active Substance: Selamectin 120mg
Excipients: Butylated Hydroxytoluene 0.08%
Legal Category:
POM-V | Stronghold for Medium Dogs
Please note: Due to current regulations, we are unable to dispatch veterinary medicines to Northern Ireland.
How to apply it
A bit of hair clumping at the spot, or a light dusting of white powder, is completely normal — it clears up within a day and doesn’t affect how well it’s working.
Handling precautions
Disclaimer: For detailed safety information, please refer to the manufacturer’s datasheet.
Packsize Option
| Active ingredient | Selamectin, 120mg |
| Suitable for | Dogs 10.1kg–20kg |
| Pipette cap colour | Red |
| Dose volume | 1.0ml |
| Legal category | POM-V (prescription required) |
| Manufacturer | Zoetis UK Limited |
Doesn’t cover: ticks. If tick protection matters where you walk your dog, you’ll want something to go with this.
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Yes. POM-V items require a valid prescription from your UK vet.
Upload your prescription during checkout.
Photos must be clear. If details are wrong or expired, orders can’t be processed. This is standard across UK pet pharmacies.
No. Under UK law, vets must provide a written prescription if you request one for a POM-V medicine. They may charge a reasonable fee for issuing it, but they cannot refuse. This allows you to choose where to buy your pet’s medication, whether directly from your vet or from a registered UK pharmacy such as Ashcroft 4 Pets.
In the UK, most POM-V prescriptions are valid for 6 months, unless your vet specifies a shorter duration. Prescriptions for Schedule 2 or 3 controlled medicines are usually valid for 28 days and are not repeatable. At Ashcroft 4 Pets, we follow these same UK veterinary guidelines to ensure your pet’s medication is dispensed safely and legally.
At Ashcroft 4 Pets, we are a fully VMD-registered and accredited online retailer. This means every prescription and over-the-counter pet medicine we supply is safe, genuine, and dispensed according to UK law.
We follow all Veterinary Medicines Directorate (VMD) rules, and our team checks every prescription carefully before processing. You can order with confidence, knowing your pet’s health is in the hands of experts and all medicines are traceable, legally supplied, and authentic.
In the UK, most repeat prescriptions for POM-V medicines are valid for up to 6 months from the date your vet issues them. You can order multiple times within this period if your vet has authorised repeats.
For controlled medicines (Schedule 2 or 3), the prescription is valid for 28 days only and cannot be repeated. These medicines are strictly regulated due to their potential for misuse.
At Ashcroft 4 Pets, we follow UK law carefully, ensuring all prescriptions are dispensed safely, legally, and in the exact amounts prescribed.
If your vet prescribes a human medicine for your pet under the Cascade, we can usually dispense against that prescription (with the right checks).
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Home/Pet Advice/Worms/How Often Does a Dog Need Worming? Vet Schedule UK Worms How Often Does a Dog Need Worming? Vet Schedule UK Reviewed by Dr Brian Faulkner, BVetMed MRCVS Clinical Lead, Ashcroft 4 Pets · RCVS Reg. 7041592 Verified Updated
Home/Pet Advice/Fleas & Ticks/Best Flea Treatment for Dogs UK Fleas & Ticks Best Flea Treatment for Dogs UK: How to Choose the Right Option Reviewed by Dr Brian Faulkner, BVetMed MRCVS Clinical Lead, Ashcroft 4 Pets · RCVS Reg. 7041592
