Trifexis (Spinosad / Milbemycin Oxime) Dosage for Dogs
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.
Dosage Calculator
Enter your dog's weight to calculate the recommended dose.
Recommended Dosage
Low Dose
—
mg
Standard Dose
—
mg
Max Dose
—
mg
Frequency
once monthly
These calculations are estimates based on standard veterinary dosing guidelines. Always confirm with your veterinarian before administering medication.
Trifexis Dosage Chart for Dogs by Weight
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| Weight | Low Dose | Standard Dose | Max Dose | 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 |
What is Trifexis (Spinosad / Milbemycin Oxime) used for in dogs?
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 of Trifexis in dogs
Common side effects
Serious side effects
- seizures (rare)
- severe vomiting
- tremors
- hypersalivation
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