Industry updates / Health Alert – Comfortis Tablets used with “off-label” worming products

Comfortis (Spinosad) Chewable Tablets are a commonly used and effective monthly tablet for the prevention and treatment of flea infestation in dogs.

Spinosad, the active ingredient in Comfortis Tablets, belongs to the family of drugs called ‘macrocyclic lactones’.

Elanco Animal Health, the manufacturer of Comfortis Tablets, has advised that dogs receiving “off-label” doses of other macrocyclic lactones (eg Ivermectin) should not be treated with Comfortis (Spinosad) Tablets simultaneously.

“Off-label” usage of any medication (including worming products) must only occur under the direction of a veterinarian. Many of these “off-label” products are manufactured for use in other species (e.g. horses, cattle). Your veterinarian can provide advice and appropriately prescribe and label the product to minimise the risk to your greyhound’s health.

Some examples of “off-label” products which are sometimes used in greyhounds and which contain macrocyclic lactones include:

  • Ivermectin (e.g. Equimax LV Oral Paste For Horses)
  • Abamectin (e.g. Equimax Liquid All Wormer for Horses)
  • Doramectin (e.g. Dectomax Injectable).

Macrocyclic lactone toxicity has been observed in dogs when Ivermectin or high doses of other macrocylic lactones are co-administered with Comfortis (Spinosad) Tablets. There has been an awareness of this drug interaction since 2008 and sporadic cases of death have been reported over this time. Dogs affected by macrocyclic lactone toxicity most frequently present with neurological signs such as trembling, an inability to stand and seizures. Symptoms may progress to coma and death in severe cases.

Never use Comfortis (Spinosad) Tablets together with “off-label” products containing Ivermectin, Abamectin or Doramectin. Monthly use of Ivermectin, Abamectin or Doramectin in greyhounds for internal worm control will not be safe if used in combination with Comfortis (Spinosad) Tablets. If Ivermectin is prescribed “off-label” by your veterinarian for worming or treating demodectic mange, consider at least a six-week delay prior to using Comfortis (Spinosad) Tablets.

There are many registered products available for the worming of greyhounds that offer a safer and more effective alternative to the “off-label” use of cattle or horse products. To reduce the risk of medication side-effects, it is best practice to choose products which are specifically designed for and registered for use in dogs.

If you have any questions or concerns, please contact the Commission’s veterinary team on 13 GWIC (13 49 42) or email