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PetDosageChart

Antiparasitic combination · For Dogs

How much Trifexis (Spinosad / Milbemycin Oxime) can I give my dog?

Standard Trifexis dose for dogs is 30 mg per kg (13.61 mg per lb), given once monthly. Use the calculator below for your dog's exact weight, or jump to the weight-by-weight chart.

Onset
30 minutes (flea killing)
Duration
30 days
Class
Antiparasitic combination

This dosage information is for educational purposes only. Always consult your veterinarian before giving any medication to your pet. Dosages may vary based on your pet's health conditions, other medications, and individual factors.

Content reviewed by licensed veterinarians. Sourced from Plumb's Veterinary Drug Handbook and the Merck Veterinary Manual.

Dosage Calculator · 01

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By Weight

Trifexis dose by dog weight

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Dosage Chart · 02

Trifexis dosage for dogs by weight

Scroll sideways to see full table

Weight Low Dose Standard Max Safe Frequency
5 lbs (2.3 kg) 69mg 69mg 138mg (140mg tablet) once monthly
10 lbs (4.5 kg) 135mg (140mg tablet) 135mg (140mg tablet) 270mg (2 × 140mg) once monthly
15 lbs (6.8 kg) 204mg 204mg 408mg (3 × 140mg) once monthly
20 lbs (9.1 kg) 273mg (2 × 140mg) 273mg (2 × 140mg) 546mg (4 × 140mg) once monthly
25 lbs (11.3 kg) 339mg 339mg 678mg (5 × 140mg) once monthly
30 lbs (13.6 kg) 408mg (3 × 140mg) 408mg (3 × 140mg) 816mg (6 × 140mg) once monthly
40 lbs (18.1 kg) 543mg (4 × 140mg) 543mg (4 × 140mg) 1086mg (8 × 140mg) once monthly
50 lbs (22.7 kg) 681mg (5 × 140mg) 681mg (5 × 140mg) 1362mg once monthly
60 lbs (27.2 kg) 816mg (6 × 140mg) 816mg (6 × 140mg) 1632mg once monthly
70 lbs (31.7 kg) 951mg (7 × 140mg) 951mg (7 × 140mg) 1902mg once monthly
80 lbs (36.3 kg) 1089mg (8 × 140mg) 1089mg (8 × 140mg) 2178mg once monthly
90 lbs (40.8 kg) 1224mg 1224mg 2448mg once monthly
100 lbs (45.4 kg) 1362mg 1362mg 2724mg once monthly
120 lbs (54.4 kg) 1632mg 1632mg 3264mg once monthly
150 lbs (68 kg) 2040mg 2040mg 4080mg (29 × 140mg) once monthly

Common Uses · 03

What is Trifexis (Spinosad / Milbemycin Oxime) used for in dogs?

flea prevention heartworm prevention roundworm treatment hookworm treatment whipworm treatment

Administration · 04

How to give Trifexis to your dog

Trifexis MUST be given with food for proper absorption — this is critical for effectiveness. Give on the same day each month. A heartworm test is required before starting. The tablet is not as palatable as some alternatives, so you may need to hide it in food or a pill pocket.

Available Forms

chewable tablet

Give with Food?

Yes — give with food

Side Effects · 05

Side effects of Trifexis in dogs

Common side effects

vomiting
decreased appetite
diarrhea
lethargy
itching

Serious side effects — call your vet

  • seizures (rare)
  • severe vomiting
  • tremors
  • hypersalivation

Emergency · 06

When to call the vet

Call your vet immediately if your dog shows any of these signs:

  • Vomiting within 1 hour of dosing
  • Seizures or tremors
  • Severe or persistent vomiting
  • You still see fleas after 24 hours
  • Lethargy lasting more than 24-48 hours

Related · 08

Related medications for dogs

Sources · 09

Sources & references

The dosage information on this page is compiled from the following veterinary and pharmaceutical references:

  • Plumb's Veterinary Drug Handbook — the standard veterinary pharmacology reference used by veterinarians worldwide.
  • Merck Veterinary Manual — a trusted, peer-reviewed resource for veterinary professionals and pet owners.
  • DailyMed (FDA Drug Labels) — official FDA-approved drug labeling and prescribing information for Spinosad / Milbemycin Oxime.

Read more about our methodology and how we calculate dosages.

Frequently Asked · 07

Questions about this medication

What does Trifexis cover?
Trifexis covers fleas, heartworm, roundworms, hookworms, and whipworms in a single monthly tablet. However, it does NOT cover ticks. If your dog is in a tick-prone area, you will need an additional tick preventive.
Why does Trifexis make my dog vomit?
Vomiting is the most commonly reported side effect of Trifexis. This is often because it was given on an empty stomach. Always give Trifexis with a full meal — this significantly reduces the chance of vomiting and is required for proper absorption.
Is Trifexis safe for dogs?
Trifexis is FDA-approved and has been used widely since 2011. It is generally safe when used as directed. The most common concern is vomiting, which is usually prevented by giving with food. Rare neurological events have been reported with spinosad-containing products.
Does Trifexis kill ticks?
No. Trifexis does not protect against ticks. You will need a separate tick preventive (such as a tick collar or an isoxazoline product like NexGard) if your dog is exposed to ticks. Consult your vet for the best combination approach.

Safety · 10

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