Masivet® information for animal owners

My pet has a mast cell tumour or mastocytoma: What now?

What is a mast cell tumour?

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

What is Masivet®?

Masivet® helps to stabilise or heal the tumour in your dog. The active substance is Masitinib, which is a Protein Tyrosine Kinase (PTK) inhibitor that acts on c-Kit. It is not chemotherapy and therefore causes minimal damage to healthy tissues. Masivet® is administered in the form of tablets. The dose is administered once a day directly before meals or during meals with some food. As with other tumor therapies, it is difficult to say whether the treatment with Masivet® will work in your dog and how long the effect of Masivet® lasts. It is therefore important to regularly visit your veterinarian at
. It is also important to have the vet check the blood values and determine whether 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 that you take some precautions when administering the medicine, handling the animal and its faeces, vomit and saliva:

  • Avoid direct contact of the tablets with the skin. Wear disposable gloves when administering.
    of the tablets and when disposing of faeces or vomit;
  • Clean up your pet's faeces;
  • Wash your hands thoroughly after stroking the dog/cat and when the dog/cat has licked you.

We recommend that the use of Masivet® be carefully considered in case of:

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

Store the tablets out of reach of children and pets. Return any unused remnants of the medicine to your vet or pharmacy for destruction. Read the leaflet carefully before use! 

What side effects may occur?

Vomiting and/or diarrhoea is a common side effect. If the tablet is regurgitated within 10 minutes of administration, treatment should be repeated
. If the tablet is regurgitated more than 10 minutes after administration, the treatment should not be repeated. Your veterinarian can prescribe an anti-vomiting medicine and/or a stomach protector if necessary.

How should I give Masivet® to my dog?

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

If you forget a dose, administer the next dose as prescribed. You should not increase or double the dose. If you have exceeded the prescribed number of tablets you should contact your vet.

How long should my dog be given Masivet®?

The duration of treatment depends on how your dog responds to the treatment. Treatment should be continued in cases of stable disease, i.e. in cases of static, partial or complete response of the tumour, 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 tumour is still growing after 4 weeks, the treatment is unlikely to be successful and should be reconsidered.

How will my dog be monitored?

Your dog will need to be seen by your vet every 2 weeks during the first 8 weeks of treatment. During these check-ups, your animal's general condition will be assessed and blood and/or urine tests will be performed. Your vet may ask you to bring your dog's urine.

Tip: Wear disposable gloves when collecting urine.

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

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


Maxani Animal Healthcare BV

Lark Avenue 14b

3704 GR Zeist


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