Mladsi D, Ramamohan V, Ronquest N, Boklage SH. A cost-consequences analysis of inpatient tolvaptan compared with fluid restriction among SIADH patients with hyponatremia. Poster presented at the 2015 AMCP Nexus; October 26, 2015. Orlando, FL. [abstract] J Manag Care Pharm. 2015 Oct; 21(10-a):S33.

BACKGROUND: Tolvaptan is a vasopressin-receptor antagonist used as an alternative to fluid restriction (FR) for the treatment of dilutional hyponatremia (HN) in hospitalized patients with syndrome of inappropriate diuretic hormone (SIADH). The efficacy of tolvaptan, compared to FR, as a treatment for HN was investigated in a prospective, multicenter, randomized, active-controlled, open-label trial (Gheorghiade et al., 2006).

OBJECTIVE: The objective of this cost-consequences study was to estimate the economic and health outcomes associated with tolvaptan, in comparison with FR.

METHODS: A decision-analytic model was developed from the perspective of a U.S. hospital system to estimate potential economic and health outcomes associated with tolvaptan compared to FR among hospitalized SIADH patients with HN. The model considers patients with severe (serum sodium [SS] levels <125 mEq/L) HN and patients with mild-to-moderate (SS levels ≥125 mEq/L) FR-resistant HN. Patients’ response to treatment with tolvaptan, based on response rates among all hyponatremic patients reported in Gheorghiade et al. (2006), was assumed not to change with HN severity. FR-resistant patients with mild-moderate HN were assumed not to respond to treatment with continued FR. The model assumes patients’ response to treatment (assessed in Gheorghiade et al., 2006) influences their health consequences: hospital length of stay, probability of an intensive care unit (ICU) admission, and probability of a 30-day all-cause hospital readmission. Health consequences data were obtained from published studies that compared patients with and without HN (Callahan et al., 2009; Deitelzweig et al., 2013).

RESULTS: Among hospitalized SIADH patients with severe HN, the model suggested that tolvaptan may yield total cost-savings of $223 per patient when compared to FR. Among hospitalized SIADH patients with mild-moderate FR-resistant HN, a total cost-savings of $966 per patient compared to continued FR. Tolvaptan drug costs were completely offset in both cases. Among hospitalized SIADH patients with severe HN, the model suggested reductions of 14.6% and 5.1% in the numbers of ICU admissions and 30-day readmissions, respectively. The model suggested reductions of 14% and 10% in the numbers of ICU admissions and 30-day readmissions, respectively, among hospitalized SIADH patients with mild-moderate FR-resistant HN.

CONCLUSIONS: As an effective treatment for HN among hospitalized CHF patients, tolvaptan, in comparison with FR, is expected to save hospitalization costs, regardless of HN severity.