Tolvaptan in Hyponatremic Cancer Patients

Inclusion Criteria:

1. Euvolemic or hypervolemic (patients with heart or liver failure) with cancer admitted to MD Anderson Cancer Center for any reasons with serum sodium between 125 and 130 mEq/L (both inclusive)
2. Patients must be greater than or equal to 18 years of age
3. Patient has an Eastern Cooperative Oncology Group (ECOG) performance status of 0-3 at baseline.
4. Women of childbearing potential must use a medically accepted method of contraception and to continue use of this method for the duration of the study and for 30 days after study participation. Acceptable methods of contraception include abstinence, barrier method with spermicide, intrauterine device (IUD), or steroidal contraceptive (oral, transdermal, implanted, and injected) in conjunction with a barrier method. Men must practice abstinence or use a barrier method of birth control, and must agree to continue use for the duration of the study and for 30 days after study participation.
5. Subjects must be able to comply with scheduled visits and follow-ups.
6. Informed consent must be signed

Exclusion Criteria:

1. History of hypersensitivity to tolvaptan
2. Patients admitted to the critical care unit.
3. Patients with renal failure(creatinine clearance less than 25 ml/min)
4. Patients with a life expectancy less than 3 months
5. Patients with volume depletion, BP \< 100/60 or urinary sodium \<20 meq/L.
6. Patients who are not able to swallow or cannot take medication through feeding tubes
7. Patients with diuretic-induced hyponatremia.
8. Patients with spurious hyponatremia
9. Patients with hyponatremia related to psychogenic polydypsia, head trauma, post operative conditions, uncontrolled hypothyroidism or cortisol insufficiency or any hyponatremia associated with the use of medication that can be safely withdrawn.
10. The use of alcohol while participating in the study
11. Currently taking demeclocycline, lithium, benzazepine derivatives, ketoconazole, grapefruit, grapefruit juice and receiving strong CYP3A inhibitors such as clarithromycin, fluconazole, voriconazole, posaconazole, itraconazole, ritonavir, indinavir, nelfinavir, saquinavir, nefazodone, and telithromycin.