It is important ro do the blood profile (complete blood count, biochem profile and thyroid levels). urinalysis and chest/abdominal x-ray films to start unraviling this problem. A MRI (brain scan) may be required to rule/out brain tumor.
There are two processes for seizures: metabolic and organic brain disease. The blood work, etc is to rule out metabolic disease(kidney/liver/infectious/etc), and the MRI is to rule out brain disease.
Cardiac disease can also cause seizures, and electrocardigram with ultrasound will be needed to characterize this problem.
As for constipation, I suggest Surfak (docusate sodium) and lactulose.
Discuss this with your vet and your pharmacist.
Dr. Van Lienden
Dr. Raymond Van Lienden DVM
The Animal Clinic of Clifton
12702 Chapel Road, Clifton
Virginia, U.S.A. 20124