Inclusion Criteria:

- Patients with medullary thyroid cancer

- Men and women from all ethnic and racial groups

- Diarrhea ( >=3 loose bowel movements per day)

- Duration of diarrhea of at least 1 week

Exclusion Criteria:

- Patients with MEN 2b (since these patients may have megacolon)

- Patients taking any clay products

- History of significant neurological or psychiatric disorders that would impede giving
consent, treatment, or follow up.

- Patients who cannot comply with medications

- Patients whose current medication schedule would not permit an approximate 2 hour
window between administration of CASAD and other scheduled medications.

- Pregnancy or lactation

- Patients receiving systemic chemotherapy (includes tyrosine kinase inhibitors)