conventional diuretics, including loop diuretics, are commonly
prescribed for heart failure (HF) patients with
volume overload.1–6 Loop diuretics are clinically useful
to reduce volume overload, but patients sometimes have an
insufficient response. In the Acute Decompensated Heart Failure
Registry (ADHERE), diuretic resistance was observed in approximately
30% of patients.7 A few therapeutic strategies, including
salt restriction, intravenous administration of loop diuretics,
and combination therapy with loop and thiazide diuretics,
have been developed to reduce resistance to loop diuretics, but
often result in unsatisfactory resolution. Moreover, administration
of high-dose loop diuretics is recognized as inducing several
adverse events, including renal impairment and hyponatremia,
with higher mortality.5,8–11 Despite this unmet medical need,
no new oral diuretics have been developed over the past decade.
Tolvaptan (Otsuka Pharmaceutical Co, Ltd, Tokyo, Japan)
is an oral arginine-vasopressin (AVP) type 2 receptor antagonist
with an aquaretic effect.12–15 Tolvaptan increases urine volume
without increasing electrolyte excretion into urine (ie, aquaresis).
14 Schrier et al have reported that tolvaptan increased serum
sodium levels consistently in patients with hyponatremia.16
Tolvaptan is indicated for patients with hyponatremia and syndrome
of inappropriate antidiuretic hormone (SIADH) in the
USA, and for SIADH in the EU.17 In Japan, tolvaptan has been
approved for “volume overload in heart failure patients when
adequate response was not obtained with other diuretics (eg,
loop diuretics)” since 2010. The approval was based on the results
from the QUalification of Efficacy and Safety in the study
of Tolvaptan in cardiac edema study (QUEST) study, in which
Matsuzaki et al reported that tolvaptan showed efficacy in HF
patients with volume overload, and that its action was not associated
with electrolyte imbalance or renal impairment.18 The
presence of worsening congestive symptoms is a leading cause
of hospitalization, and reduction in the patient’s quality of life.19
In the QUEST study, improvement of congestive symptoms was
also reported.18
However, the applicability of the results of the QUEST study
is limited by the clinical trial’s strict inclusion and exclusion
criteria for enrollment. Therefore, it is desirable to confirm
whether the efficacy and safety features of tolvaptan in clinical
trials can be extended to real-world clinical settings. Hence the
aim of this study was to provide efficacy and safety data from
post-marketing surveillance of tolvaptan in HF patients with
volume overload. Hypernatremia is a major and unique concern
with tolvaptan because of its aquaretic nature, and a risk analysis
was executed to predict the occurrence of hypernatremia
after tolvaptan treatment