You should speak with the vet who prescribed it.
From this link:
Incurin - Product Data Sheet
Adverse reactions (frequency and seriousness)
Oestrogenic effects such as swollen vulva, swollen mammary glands and/or attractiveness to males and vomiting have been observed at the highest recommended dose of 2 mg per dog. The incidence is about 5-9 %. These effects are reversible after lowering the dose.