SAMSCA is indicated for the treatment of clinically significant hypervolemic and euvolemic hyponatremia (serum sodium <125 mEq/L or less marked hyponatremia that is symptomatic and has resisted correction with fluid restriction), including patients with heart failure, cirrhosis, and Syndrome of Inappropriate Antidiuretic Hormone (SIADH). Thiis condtion occurrs with lung cancer and less commonly other cancer or in associaitons with certain chemotherapy drugs that are used to treat cancer, such as cisplatin.
SAMSCA should be initiated and re-initiated in patients only in a hospital where serum sodium can be monitored closely. This allows observing for side efects and to titrate to an appropraite dose. The FDA aproved Prescribing information says: “The usual starting dose for SAMSCA is 15 mg administered once daily without regard to meals. Increase the dose to 30 mg once daily, after at least 24 hours, to a maximum of 60 mg once daily, as needed to achieve the desired level of serum sodium. ”
Cavalcante JL, Khan S, Gheorghiade M EVEREST study: Efficacy of Vasopressin Antagonism in Heart Failure Outcome Study with Tolvaptan. Expert Review of Cardiovascular Therapy 2008 Nov;6(10):1331-8
Madias NE Effects of tolvaptan, an oral vasopressin V2 receptor antagonist, in hyponatremia. American Journal of Kidney Diseases: the Official Journal of the National Kidney Foundation 2007 Aug;50(2):184-7
Miyazaki T, Fujiki H, Yamamura Y, Nakamura S, Mori T Tolvaptan, an orally active vasopressin V(2)-receptor antagonist – pharmacology and clinical trials. Cardiovascular Drug Reviews 2007 Spring;25(1):1-13
Konstam MA, Gheorghiade M, Burnett JC Jr, Grinfeld L, Maggioni AP, Swedberg K, Udelson JE, Zannad F, Cook T, Ouyang J, Zimmer C, Orlandi C; Efficacy of Vasopressin Antagonism in Heart Failure Outcome Study With Tolvaptan (EVEREST) Investigators Effects of oral tolvaptan in patients hospitalized for worsening heart failure: the EVEREST Outcome Trial. JAMA : the journal of the American Medical Association 2007 Mar 28;297(12):1319-31
Read the Layperson version here.