Masivet® information for pet owners.

My pet has a mast cell tumor or mastocytoma: Now what?


What is a mast cell tumor?

Mast cell tumors are the most common skin tumors in dogs and the second most common skin tumors in cats. Mast cells normally help fight infections and play an important role in allergic reactions. When the division of these mast cells goes haywire, we speak of a
mast cell tumor.

What is Masivet®?

Masivet® helps stabilize or cure the tumor in your dog. The active ingredient is Masitinib, which is a Protein Tyrosine Kinase (PTK) inhibitor that acts on c-Kit. It is not a chemotherapy and therefore causes minimal damage to healthy tissues. Masivet® is administered in the form of tablets. The dose is administered once a day immediately before meals or during meals with some food. As with other tumor therapies, it is difficult to say whether treatment with Masivet® will work in your dog and how long the effect of Masivet® will last. Therefore, it is important to check in regularly with
your veterinarian. It is also important to have your veterinarian check the blood levels and determine if the dose of Masivet® needs to be adjusted.

Precautions when using Masivet®.

The active substance in Masivet® belongs to the risky substances for animals and humans. Therefore, we recommend observing some precautions when administering the drug, handling the animal and his/her feces, vomit and saliva:

  • Avoid direct contact of tablets with skin. Wear disposable gloves when administering.
    tablets and cleaning up feces or vomit;
  • Clean up your pet's feces;
  • Wash your hands well after petting the dog/cat and when the dog/cat licks you.

We recommend careful consideration of the use of Masivet® when:

  • Households with pregnant or lactating women;
  • Households with people with poor health;
  • Dogs that tend to lick the people/children in the household a lot.

Store tablets out of reach of children and pets. Return leftover drug that is no longer used to your veterinarian or pharmacy for destruction. Read the package insert carefully before use! 

What side effects may occur?

Vomiting and/or diarrhea is a common side effect. If the tablet is vomited within 10 minutes of administration, treatment should be
repeated. If the tablet is vomited more than 10 minutes after administration, treatment should not be repeated. Your veterinarian may prescribe an anti-vomiting agent and/or a stomach protector if needed.

How should I give Masivet® to my dog?

Always wear (disposable) gloves when administering the tablets. Tablets should be given once a day before or during meals and should be given whole. Tablets should not be divided, broken or crushed. Broken tablets that are spit out after chewing by the dog should be discarded (take leftovers to your veterinarian or pharmacy for destruction). Wear gloves when doing this, too.

If you forget a dose, administer the next dose as directed. You should not increase or double the dose. If you have administered more than the prescribed number of tablets, you should contact your veterinarian.

How long should my dog be given Masivet®?

The duration of treatment depends on how your dog responds to treatment. Treatment should be maintained in case of stable disease, that is, in case of static, partial or complete response of the tumor, provided that the product is sufficiently well tolerated. In this case, treatment is given for 6 to 12 months. Treatment should be evaluated after 4 weeks to assess the initial response. If the tumor is still growing after 4 weeks, the treatment is probably not responding and should be reviewed.

How will my dog continue to be monitored?

Your dog will need to visit your veterinarian every 2 weeks for the first 8 weeks of treatment. At these checkups, your pet's general condition will be reviewed and blood tests and/or urinalysis will be done. Thus, your veterinarian may ask you to bring urine from your dog.

Tip: Wear disposable gloves when collecting urine.

After these 8 weeks, visit your veterinarian at increasingly longer intervals (at least monthly), depending on how your animal is doing.
Long-term treatment should only be done under the strict supervision (at least monthly) of your veterinarian.

Do you have further questions? Please contact your attending veterinarian!